7.3 Congenital adrenal hyperplasia in children

Congenital adrenal hyperplasia (CAH) is caused by the genetic impairment of one of the five enzymes required for the biosynthesis of cortisol from cholesterol. In 95% of cases 21-hydroxylase deficiency (21-OHD) is responsible for the disease (1). Classic 21-OHD has an incidence varying from 1:11 800 to 1:21 800, depending on the population background. The pathophysiology, clinical picture, genetics, and the unique aspects of management from the point of view of the paediatric endocrinologist are addressed, and the problems encountered from birth to puberty are described. The child specific issues of rare forms of CAH are summarized thereafter. The reader is referred to Chapter 5.11 for a comprehensive overview of 21-OHD and for more details on all other forms of CAH.

CAH due to 21-OHD results in a state of hypocortisolism, hypoaldosteronism, and hyperandrogenism, combined with epinephrine deficiency and related metabolic disturbances. The adrenal biosynthesis of the glucocorticoid, cortisol, is regulated by negative feedback on the secretion of hypothalamic corticotropin-releasing hormone (CRH) and pituitary adrenocorticotropic hormone (ACTH). Insufficient cortisol biosynthesis leads to an increase in CRH and ACTH secretion, which chronically stimulates the adrenal cortex, resulting in the pathological finding of hyperplastic adrenal glands. Cortisol and aldosterone biosynthesis are deficient because of a disturbance in the enzymatic conversion of the steroid precursors progesterone to 11-deoxycorticosterone and of 17-hydroxyprogesterone to 11-deoxycortisol (Fig. 7.3.1). These reactions are catalysed by the microsomal cytochrome P450 enzyme 21-hydroxylase, which is expressed and translated exclusively in the adrenal cortex. The steroid precursors, progesterone and 17-hydroxyprogesterone, accumulate, and are shunted into adrenal androgen biosynthesis, leading to elevated levels of androstenedione, testosterone, dihydrotestosterone, and peripherally aromatized oestrogens. Steroid biosynthesis and its regulation by the hypothalamic-hypophyseal-adrenal axis are active from an early postconceptional age. 21-OHD is therefore effective prenatally and its reduced activity in CAH causes virilization of the fetus. Adrenocortical glucocorticoids are essential for the development of the adrenal medulla and for its function of synthesizing epinephrine. Without endogenous cortisol the organogenesis of the adrenal medulla is severely disturbed, resulting in epinephrine deficiency (2).

CAH due to 21-OHD covers a clinical continuum from the severe classical salt-wasting form to the less severe simple virilizing 21-OHD, and to the nonclassical forms, which manifest during early adolescence or adulthood. The classical forms are characterized by an increase in androgen biosynthesis, and decreased cortisol and aldosterone secretion (Fig. 7.3.2). All female patients exhibit some degree of ambiguous external genitalia. The severity of virilization is classified in five stages defined by Andrea Prader, ranging from a simple clitoromegaly (Prader stage 1) to a complete fusion of the labial folds and a penile appearance of the clitoris resembling normal male genitalia (Prader stage 5) (Fig. 7.3.3). The internal genital organs, uterus, fallopian tubes, and ovaries show normal female differentiation. Boys with 21-OHD may show completely normal external genitalia or various degrees of hyperpigmentation as a result of elevated androgen levels. Two out of three patients suffering from classical 21-OHD are prone to salt-losing episodes after birth and later, due to insufficient aldosterone biosynthesis. The clinical correlate is life-threatening hyponatremia, dehydration, and shock. The most severe clinical phenotype is known as salt-wasting 21-OHD. There is no correlation between the severity of the salt-wasting and the degree of virilization. The remaining third of patients with classical 21-OHD produces sufficient aldosterone to prevent salt-losing crises. However, these patients almost always present with elevated plasma renin activity, suggesting a compensated sub-clinical salt loss. Since virilization is the only overt clinical sign in these patients, this subgroup is referred to as simple virilizing. Without medical treatment, patients with classical salt-wasting 21-OHD will either die after birth or show progressive virilization with precocious pseudopuberty, frequently leading to central precocious puberty and diminished adult height. Nonclassical 21-OHD is caused by a partial deficiency of 21-hydroxylase activity, which results in late-onset of milder clinical symptoms without prenatal virilization. Postnatal presentation usually becomes obvious in the peripubertal period, with premature pubarche, tall stature, advanced bone age, menstrual irregularities, infertility, hirsutism, and acne.

The 21-hydroxylase coding gene CYP21A2 is located on chromosome 6p21.3 within the HLA histocompatibility complex. The CYP21A2 gene codes for active 21-hydroxlyase, whereas CYP21A1 is a highly homologous, but inactive pseudogene. Most mutations of the active CYP21A2 gene are generated by recombination events between the active and the inactive gene. The mutations enclose single point mutations, intronic changes, and complete gene deletions or conversions (1). Depending on the residual activity of the mutant protein, there is a good correlation between genotype and phenotype with regard to salt-loss (Fig. 7.3.4). Large gene deletions and point mutations with no measurable enzyme activity are associated with salt-wasting 21-OHD. Mutations that lead to 1–2% residual enzyme activity allow sufficient aldosterone biosynthesis to prevent salt-loss, and result in simple-virilizing forms of 21-OHD. The correlation between genotype and genital phenotype is less obvious, and appears to be modified by additional genetic or epigenetic factors. Nonclassical forms are caused by mutations with up to 60% residual enzyme activity. Most patients are so-called compound heterozygotes, carrying one or more different mutations on each allele. In such cases, the severity of the disease depends on which mutation has the greater residual activity.

The first goal in the management of 21-OHD in infancy and childhood is to obtain the earliest possible accurate diagnosis of the disease. Genital virilization or a salt-losing crisis should alert the midwife and paediatrician either to diagnose or rule out 21-OHD (Fig. 7.3.5). Whereas genital ambiguity in 46,XX individuals is obvious at birth and will initiate prompt further diagnostic work up, salt-losing crises generally occur in the second week of life, at a time when the neonate is already discharged from hospital. Since the clinical signs are vomiting, diarrhoea, and dehydration, such infants are occasionally thought to have viral gastroenteritis or intestinal obstruction, and delayed treatment may result in the infant’s death. Thus, the main aim of newborn 21-OHD screening is to prevent neonatal deaths due to salt-losing crises, particularly in boys, who otherwise manifest no signs of the disease. CAH due to 21-OHD deficiency can be diagnosed in modern newborn screening programmes by detecting 17-hydroxyprogesterone concentration in dried blood spots. Apart from reducing neonatal mortality, early diagnosis through newborn screening can also be assumed to have an effect on the consequences of virilization and long-term outcome, particularly for male patients with simple virilizing forms.

If cases are not diagnosed by newborn screening, simple virilizing boys usually manifest at 3–7 years, when they present with iso-sexual precocious pseudopuberty, tall stature, and advanced bone age. Diagnosis can be made by a basal measurement of 17-hydroxyprogesterone. In such cases a stimulation test with synthetic ACTH(1–24) is not necessary. The measurement of plasma renin activity helps to verify a subclinical salt-loss and in those with raised levels mineralocorticoid treatment can be initiated. The diagnosis of nonclassical 21-OHD in peripubertal, teenage and adult patients requires the detection of 17-hydroxyprogesterone and adrenal androgens in response to intravenous synthetic ACTH(1–24). The usual dose is 125 µg ACTH(1–24) up to 1 year of age and 250 µg ACTH(1–24) in older children and adults. Androgens, cortisol, and 17-hydroxyprogesterone are measured at baseline and after 60 min and the responses must be compared with age- and sex-specific data from healthy children. The cortisol response to ACTH is normal in nonclassical 21-OHD, whereas the response of 17-hydroxyprogesterone is increased to >30 nmol/L. Adrenal androgens, such as dehydroepiandrosterone and androstenedione, are usually elevated.

The correct measurement of the marker steroid 17-hydroxyprogesterone is vital for the diagnosis of 21-OHD. Various techniques for measuring 17-hydroxyprogesterone are available. The routine methods applied in screening overestimate the 17-hydroxyprogesterone levels due to insufficient antibody specificity and, especially in neonates, to cross-reacting steroid hormones of fetal adrenal origin; prematurity and critical illness also cause elevated 17-hydroxyprogesterone levels. For these reasons various cut-off levels based on birthweight or on gestational age have been established. The problem of false-positive results in premature or stressed newborns can be overcome by using steroid profiles, and more specific methodology, such as liquid chromatography-mass spectrometry. Molecular genetic diagnostics are not necessary for the diagnosis of 21-OHD. However, knowledge of the exact individual genotype is helpful for genetic counselling, future prenatal diagnostics, and therapy, as well as for predicting the severity of the disease in individual cases.

Glucocorticoid treatment of pregnant mothers at risk for classic 21-OHD was first described in the 1980s. After crossing the placental barrier dexamethasone suppresses the fetal hypothalamus-pituitary-adrenal axis, thus preventing genital ambiguity in about 85% of cases of females with 21-OHD. However, only affected female fetuses need therapy. Because of the autosomal recessive mode of inheritance, there is a risk of treating seven out of eight fetuses unnecessarily. Dexamethasone is administered in a dose of 20 µg/kg/day divided into three equal doses immediately after pregnancy is noticed, ideally before the 6th week of gestation (Fig. 7.3.6). Genetic analysis by chorionic villous sampling can be performed at 9–11 weeks of gestation. In the case of an affected female fetus dexamethasone treatment is continued until birth. In all other cases, dexamethasone can be discontinued. Treated children showed normal pre- and postnatal growth, and there was no increase in the number of congenital malformations. Documented rare mild adverse effects could not be clearly attributed to the dexamethasone medication. The treated mothers reported side effects, such as increased weight gain, oedema, and striae, but there is little long-term follow-up data on prenatal dexamethasone therapy. Only a few follow-up studies on cognitive development have been performed and the results are controversial, most probably due to the small number of probands enrolled and the different psychological work-ups. Prenatal dexamethasone in pregnancies at risk is therefore still considered experimental.

The aim of medical treatment during childhood is to adequately suppress adrenal androgens with glucocorticoids without impairing growth, but still allowing normal pubertal development and fertility. The glucocorticoid dose has to exceed the physiological cortisol secretion rate of about 6 mg/m² per day in order to suppress elevated CRH and ACTH levels. Hydrocortisone is the preferred substance for use during childhood because it is identical to physiologic cortisol which has a short half-life. The recommended dose ranges from 10 to 15 mg/m² hydrocortisone equivalent per day (3). The need for glucocorticoids is usually higher during the first postnatal weeks, but it is important to lower the initial dose shortly thereafter in order to promote good growth. Following a period of relatively low demand for glucocorticoids for androgen suppression during childhood, the need increases during puberty. Various dose distributions are used, ranging from twice a day to four times a day. It is still questionable whether outcomes are better when the highest dose is taken in the morning or in the evening. Although regimens using long-acting glucocorticoids, such as prednisone or dexamethasone, appear to be possible in principle, they are not routinely used before the epiphyseal growth plates have fused. Therapy can be monitored through 24-h urinary steroid profiling, saliva steroid measurements, or plasma steroid detection. The urinary profile serves as an integral parameter for therapy adjustment. Repeated saliva measurements of 17-hydroxyprogesterone can reveal an inadequate dose distribution throughout the day. Plasma steroids reflect the short-term status, but are useful if adrenal androgens, such as androstenedione, are measured. Age- and sex-specific normative data for each method are necessary for the final assessment. Growth monitoring (height and height velocity) and bone maturation (bone age) remain the gold standards for controlling medical treatment in 21-OHD.

All patients suffering from 21-OHD show a sub-clinical salt loss regardless of the clinical phenotype, and a mineralocorticoid is therefore administered in cases of clinically manifest salt-wasting, as well as in simple virilizing CAH with raised rennin levels. Mineralocorticoid replacement reduces the need for glucocorticoids and improves linear growth. Standard doses of 100 to 200 µg/day fludrocortisone are sufficient, although higher doses of up to 400 µg/day are needed during infancy as the renal capability to retain salt is immature during the first year of life. Additional salt supplementation (1–2 g NaCl/day) may be helpful. Therapy can be monitored by measuring blood-pressure and plasma renin activity, which should be in the mid-normal range for age.

Patients suffering from classical 21-OHD are unable to produce sufficient amounts of cortisol in response to physical stress. Elevated pharmacological doses of hydrocortisone are therefore necessary during episodes such as febrile illness, surgery, or trauma. Recent studies endorse the recommendation to triple the hydrocortisone maintenance dose (4). If a patient is unable to take oral medication, intramuscular, or rectal administration is advised in an emergency and prompt hospitalization is advocated. A manifest Addisonian crisis requires higher hydrocortisone doses, e.g. a single dose of 15 mg/m² followed by a continuous intravenous infusion of 150 mg/ m² per day.

CAH due to 21-OHD leads not only to insufficient adrenal steroid biosynthesis, but also to a developmental defect in the formation and function of the adrenal medulla (2). Physical stressors not only aggravate a rise in plasma cortisol, but also induce catecholamines, which increase heart rate and blood pressure, and activate metabolic pathways, such as lipolysis, ketogenesis, thermogenesis, and glycolysis. The latter is mainly influenced by epinephrine. Epinephrine production in response to various forms of exercise is severely impaired in 21-OHD patients and no exercise-induced increase in blood glucose levels is reported. Thus, 21-OHD patients might be at risk of hypoglycaemia during physical exercise and other stressful conditions. Infants are especially prone to hypoglycaemia, as epinephrine is one of the most important triggers for a rise in blood glucose at this age.

Hyperandrogenism cannot be controlled without administering supraphysiological doses of glucocorticoids, thus inducing a state of hypercortisolism, resulting in reduced final height with more or less pronounced signs of virilization. One experimental treatment regimen involves blocking excess sex steroid action, making it possible to lower the glucocorticoid dosage (5). The therapeutic concept includes the anti-androgen flutamide, the aromatase-inhibitor testolactone and a reduced dose of hydrocortisone and fludrocortisone. Long-term results are still pending. In general, hepatotoxicity with anti-androgens and aromatase-inhibitors is still a concern and requires rigorous monitoring. Adrenalectomy is another experimental treatment possibility in cases where standard therapy has failed. This cures androgen excess, but patients are subsequently even more prone to adrenal crises. Lifelong substitutive therapy with glucocorticoids, mineralocorticoids, and probably adrenal androgens is crucial.

Increased adrenal stimulation due to insufficient cortisol biosynthesis in 21-OHD causes excessive prenatal production of adrenal androgens. Androgens cause genital virilization, ranging simply from clitoral enlargement to apparently male external genitalia. The management of the newborn child with ambiguous genitalia and counselling of the parents remain difficult and challenging. Regardless of all theoretical road-maps, an individual approach that depends on individual attitudes, experience and cultural background is essential. Although sex assignment should be postponed until sufficient information on the underlying disease can be gathered, it is understandable that the parents will wish to assign a sex to the newborn as early as possible, and a thorough and efficient work-up is therefore necessary. The diagnosis of 21-OHD or other forms of CAH can be completed within 24 h by measuring a baseline or ACTH-stimulated steroid profile. Additional tests are ultrasonography of the internal genitalia and analysis of the karyotype.

Today, 46,XX individuals with 21-OHD are almost always assigned to the female sex as they are diagnosed early, have intact gonads, uterus and vagina, feminize during puberty and can be fertile. However, it must be borne in mind that the decision about sex assignment should not be based only on the appearance of the external genitalia before or after surgery, or on the karyotype or the hormonal status, as there is no correlation between genital and brain masculinization. Unfortunately, there is no way to predict whether an individual will have gender identity problems in the future, which is why some adult 21-OHD patients advocate postponing the decision until the patient is able to give informed consent to medical treatment. However, the psychosocial problems that might arise from this approach are completely unknown and most professionals advise making an early decision on sex assignment. The decision-making process should always be supported by an experienced team comprising an endocrinologist, geneticist, urologist, or surgeon and a psychiatrist.

Various studies have shown that 46,XX 21-OHD patients raised as females display masculinized behaviour with regard to toys, play, playmates, and other activities (6). However, masculinized behaviour is not an indication of gender identity problems. Data from a meta-analysis of gender identity in 21-OHD show that 5% of 46,XX females reported problems such as uncertainty about their identity or gender dysphoria (7). One-third of these cases wanted to change their gender. 12.5% of 46,XX males reported gender identity problems. However, the meta-analysis showed no significant difference between 46,XX males and females. Furthermore, there is no obvious relationship between the degree of genital masculinization and the prevalence of gender identity problems.

Two issues are important when considering feminizing surgery for virilized female patients with 21-OHD. First, surgery creates a potentially irreversible genital status. There is no evidence that surgery to render the genital appearance compatible with sex of rearing improves psychological or psychosexual outcome, or promotes a stable gender identity. The parents must be informed that some groups and professionals discourage genital surgery until the child is old enough to decide for itself. They should be supported in making a decision with which they will be comfortable, in the almost certain knowledge that they and the surgeons will one day be criticized by the patient, whatever decision has been reached.

Secondly, the timing of surgery has to be discussed. The current advice is that once agreement for surgery between the interdisciplinary medical team and the parents has been reached, it should be performed as soon as is feasible. However, opinions vary as to whether surgery should be carried out in one or more stages, and whether vaginal reconstruction should be attempted during infancy or adolescence. Data on these issues are scarce and the operative results are highly dependent on the experience of the surgeon. The frequency of postoperative vaginal stenosis ranges from 0 to 77% (8). If vaginal reconstruction is performed during infancy, vaginal dilatation is contraindicated during childhood, although this procedure is often useful in adolescence and in adulthood. In many cases, subsequent vaginoplasties are necessary after puberty.

In view of the difficulties involved, the most important point is to be cautious when considering the indication for genital surgery. A decision should not be taken during the first weeks of life as the stimulated genital tissues will regress under the glucocorticoid therapy and genital appearance can change dramatically. The extent of ambiguity, clitoromegaly, and posterior fusion must be carefully evaluated to determine whether genitoplasty, including clitoral reduction, should be considered at all. An obstructed urinary outflow path can lead to early surgery to decrease the risk of recurrent urinary tract infections; however, urinary tract obstructions are rarely seen. Girls with a mild to moderate degree of clitoromegaly should not be operated upon because of the potential risk of compromising genital sensitivity.

One of the main goals in the management of children with 21-OHD is to achieve normal growth. Untreated patients with CAH have extremely short stature in adulthood. Final height in treated patients with 21-OHD is also compromised if compared to the general population or mid-parental height (Fig. 7.3.7) (9). The mean final height SDS corrected for target height ranges from –0.9 to –1.21. It is not entirely clear which factors contribute to this and which is the most relevant. Possible elements are clinical phenotype, mid-parental height, age at start of treatment, hormonal control and glucocorticoid dosage.

Neonates with classic 21-OHD show a significantly greater birth length and weight than the population mean (10). This is most probably due to prenatal androgen excess affecting intrauterine growth. Interestingly, untreated patients with simple virilizing 21-OHD show a normal growth pattern and no signs of androgen excess until age 18 months. However, growth in infancy is closely related to glucocorticoid dosage. If treated with supraphysiological glucocorticoid doses of up to 40 mg/m² hydrocortisone, infants can lose up to 3 SDS until the age of one (9). With less hydrocortisone, the loss in height SD during infancy is reduced.

The impact of onset of puberty and pubertal growth on final height in 21-OHD has not yet been established. Early onset of puberty combined with a normal growth spurt (11) or reduced growth spurt (12), normal onset of puberty with an increased growth spurt (9) as well as delayed puberty with reduced growth spurt (13) have all been reported. Again, glucocorticoid dosing is critical for growth in puberty, with higher hydrocortisone doses responsible for smaller stature in adulthood. The risk of growth impairment is even greater with potent long-acting glucocorticoids, such as prednisone or dexamethasone, as these drugs have only a small therapeutic index. All glucocorticoids interfere with the growth hormone axis, impairing spontaneous growth hormone secretion, as well as stimulated growth hormone secretion (14). In addition, target tissues such as the epiphyseal growth plate show a diminished response to growth factors during glucocorticoid treatment. Elevated androgens with 21-OHD and the therapeutic use of glucocorticoids in supraphysiological doses can both negatively affect final height. Additional factors resulting in poor height outcome are the late initiation of therapy, as well as poor compliance. The most critical periods during which optimal glucocorticoid dosage is vital are the first year of life, and the prepubertal period between 8 years of age and the start of puberty (15).

Since glucocorticoid therapy is one of the major parameters that influences growth, improved dosage strategies, as well as alternative treatment regimens, such as adrenalectomy, or the use of antiandrogens and aromatase inhibitors, may improve final height in 21-OHD. However, these treatments are experimental. Another approach to improving final height in 21-OHD in subjects with poor height prediction and central precocious puberty is combined treatment with GnRH agonists (GnRHa) and growth hormone. With this combination therapy CAH patients can gain +1 SD score compared with untreated subjects (16). This regimen is at most an experimental second line treatment, which might be beneficial in some selected patients after standard glucocorticoid therapy has failed (Fig. 7.3.8).

Suppressive therapy with hydrocortisone is especially challenging during puberty. Traditionally, this has been attributed to pubertal behaviour and the resulting problems with compliance. However, there is increasing evidence that pharmacokinetics of glucocorticoids are influenced by the changes in the endocrine milieu during puberty (17). Elevated growth hormone and IGF-1 levels are incriminated in diminished 11β-HSD type I activity and increased glomerular filtration capacity, which lead to accelerated cortisol clearance. At the same time, elevated growth hormone and IGF-1 levels during adolescence lead to increased 17-hydroxylase/17,20-lyase activity combined with diminished 3β-HSD type II activity, resulting in increased adrenal androgen biosynthesis. This may partly explain why adolescent subjects with hitherto well controlled 21-OHD present with overt signs of hyperandrogenaemia. In cases where problems with compliance are assumed, a switch to longer-acting glucocorticoids, such as prednisone or dexamethasone, can be advantageous near to or after closure of the epiphyseal growth plates.

If therapy of 21-OHD is well controlled during childhood and sufficient to allow a normal growth pattern, pubertal development generally starts at the appropriate age. Most studies report a normal age for menarche in CAH girls at around 12–13 years (18). Delayed menarche in 21-OHD is associated with poor therapeutic control, as is menstrual irregularity in adolescent girls and women. There is not much data on male pubertal development, but one may assume that glucocorticoid therapy in 21-OHD also influences the onset of male puberty. Contrary to delayed menarche with undertreatment, inadequate glucocorticoid replacement therapy for a prolonged period during childhood can lead to a switch from iso- or heterosexual precocious pseudo-puberty to central precocious puberty. An excess of adrenal androgens promotes skeletal maturation and early signs of secondary sexual characteristics, which defines the picture of precocious pseudopuberty in CAH. Central puberty generally starts at a bone age of 11–13 years, even if the chronological age is significantly younger.

Data on adolescent sexuality in 21-OHD is not available and can only be deduced from adult studies. Questionnaires have revealed that sexual function is much lower in 21-OHD than in controls, with the lowest indices in cases in high Prader categories (19). Clitoral and vaginal sensitivity, including thermal, vibratory, and light-touch sensory thresholds may be severely disturbed. Age at first intercourse is not significantly different in patients with Prader stages I–III and healthy controls, but, as might be expected, females with Prader stage IV–V were significantly older. Satisfaction with height, body hair, external genitalia, sexual fantasies, and sexual interest appear not to be different in patients with 21-OHD, but the latter are less satisfied with their total physical appearance in adulthood. Data regarding body perception in adolescent patients reveal that 21-OHD girls, in particular, are at risk of developing a negative body image during puberty (20).

Fertility in women suffering from classical or nonclassical 21-OHD is reduced. Although fertility is generally not a paediatric concern, most CAH fertility problems have their origins in childhood. Well-described reasons are severe hormonal imbalances in classic 21-OHD, polycystic ovary syndrome as part of the metabolic syndrome and deficient surgical genital reconstruction techniques. Fertility in males with 21-OHD is frequently impaired due to testicular adrenal rest tumours. These tumours most probably arise from cells with mixed adrenal and Leydig cell properties, which produce all the major adrenal steroids. The impairment of the local steroid hormone milieu in the testis results in oligo- or azoospermia. Long-acting glucocorticoids may reverse infertility and reduce the size of the tumour. Testis-sparing surgery does not generally improve pituitary-gonadal function, even when the tumour itself is removed. Testicular adrenal rest tumours can be detected during childhood and adolescence, and impair Leydig and Sertoli cell function, as demonstrated by reduced inhibin B, anti-müllerian hormone and testosterone levels (21). Semen conservation should be considered in late adolescence or early adulthood because of the high incidence of such tumours.

It has recently been recognized that patients with 21-OHD may be at risk for long-term metabolic problems. Pre-pubertal children and adolescents with 21-OHD are more obese than healthy subjects, with significantly higher body mass indices (BMI), and subscapular and triceps skinfold thickness (22). This is due to a higher fat mass, since bone mineral density and lean body mass are comparable with that in healthy subjects. The increased fat mass is associated with elevated fasting serum insulin, leptin, and testosterone concentrations (23). The impaired leptin regulation is potentially influenced by the dysfunction of the adrenal medulla. Glucocorticoid therapy further aggravates hyperinsulinism. Insulin and leptin stimulate adrenal and gonadal steroidogenesis, contributing to the development of polycystic ovary syndrome (PCOS), which is found in up to 76% of postmenarcheal patients (24). PCOS in adolescence can already be detected in 40% of patients. Blood pressure measured by 24-h ambulatory monitoring is significantly elevated in children and adolescents with 21-OHD (25). This is not correlated with hydrocortisone or fludrocortisone doses, but with leptin and insulin levels, as well as with the degree of overweight and obesity.

Increased BMI, high fat mass, insulin resistance, hyperandrogenaemia, increased blood pressure, and PCOS are found already in adolescent patients with 21-OHD. All these metabolic abnormalities resemble the features of the metabolic syndrome and are independent risk factors for cardiovascular disease. Since no data on morbidity and mortality in adult patients are available, the question as to whether 21-OHD comprises an elevated risk for cardiovascular disease cannot be answered. However, it would appear expedient to take measures to prevent the development of these potential risk factors during childhood and adolescence.

The rare forms of congenital adrenal hyperplasia comprise approximately 5% of defects in steroidogenesis. Most of these diseases include insufficient biosynthesis of cortisol. Because of this, the pituitary secretes increased levels of ACTH, promoting adrenal hypertrophy and hyperplasia. Depending on the inactivated enzyme (Fig. 7.3.1), these forms of CAH present additionally as 46,XY disorders of sex development or 46,XX disorders of sex development (Table 7.3.1).

Decreased androgen biosynthesis in 46,XY individuals is present in 20, 22-desmolase deficiency, steroid acute regulatory protein (StAR) deficiency, 3β-hydroxisteroid dehydrogenase deficiency, 17α-hydroxylase deficiency^/17,20-lyase deficiency, as well as P450 oxidoreductase deficiency.

The enzyme 20,22-desmolase, also called P450scc (side chain cleavage), is responsible for the conversion of cholesterol to pregnenolone. This reaction takes place at the inner mitochondrial membrane. The mitochondrial membrane is nearly impermeable to cholesterol. Hence, the steroid acute regulatory (StAR) protein facilitates the transmembraneous shuttling of cholesterol (39). Deficiency of 20,22-desmolase, as well as StAR deficiency, cause insufficient synthesis of all adrenal and gonadal steroids. In the case of StAR deficiency cholesterol accumulates within the steroidogenic cell causing the histological picture of lipoid adrenal hyperplasia (7). The adrenal glands in 20,22-desmolase deficiency are usually not detectable or small on ultrasound or MRI. The typical patient with 20,22-desmolase deficiency and StAR deficiency manifests in the neonatal period, or during early infancy with severe salt loss and glucocorticoid deficiency (24, 29). Several children with 20,22-desmolase deficiency have been born prematurely, because the inactivated enzyme interferes with normal placental steroid biosynthesis. As placental steroid biosynthesis is not dependent on StAR, StAR deficiency by itself does not cause prematurity. The lack of adrenal and gonadal androgen formation usually generates a lack of virilization in 46,XY children. Of note, single cases with 46,XY karyotype and normal male external genitalia and partial StAR deficiency have been recently reported (3). In contrast to 20,22-desmolase genetic females with StAR deficiency may have spontaneous onset of puberty with thelarche and even menarche. However, premature ovarian failure is usually reported. The diagnosis of 20,22-desmolase and StAR deficiency can be established with low basal levels of adrenal and gonadal steroids together with highly elevated levels for ACTH and renin. The accurate differential diagnosis can be only made with molecular genetics. The enzyme 20,22-desmolase is coded by the CYP11A1 gene. The StAR protein is coded by the StAR gene. Both diseases follow an autosomal recessive trait. The therapeutic strategy during infancy consists of hydrocortisone and fludrocortisone in replacement dosages. Monitoring treatment includes clinical parameters, such as growth, weight, bone age, as well as laboratory parameters, such as ACTH, free cortisol in 24-h urine samples, renin, and electrolytes. Puberty has to be induced with oestrogens. Genetic males with female phenotype are raised as females and should undergo orchidectomy because of the risk of gonadoblastoma.

The nicotinamide-adenine-dinucleotide (NAD) dependent membrane bound enzyme 3β-hydroxysteroid dehydrogenase type II is responsible for the oxidation and Δ4-isomerization of the Δ5-steroid precursors pregnenolone, 17-hydroxypregnenolone, dehydroepiandrosterone, and androstenediol into the respective Δ4-steroids progesterone, 17-hydroxyprogesterone, androstenedione, and testosterone in the adrenals and gonads (36). The clinical phenotypes of classic 3β-hydroxysteroid dehydrogenase type II vary with salt-losing and non-salt-losing forms (6). Both forms of classic 3β-hydroxysteroid dehydrogenase type II deficiency can manifest with adrenal crisis. Genetic males show a disorder of sex development because of the insufficient adrenal and gonadal androgen synthesis. The clinical consequences are different degrees of hypospadias often accompanied by maldescended testes. In contrast, genetic females show minor forms of virilization due to direct action and peripheral conversion of dehydroepiandrosterone by the iso-enzyme 3β-hydroxysteroid dehydrogenase type I. The salt-losing form is easily detected within the first weeks of like. The non-salt-losing form in 46,XY patients is apparent because of the genital abnormalities. The disease may go undetected with a 46,XX karyotype until a premature adrenarche develops. Single cases with normal isosexual puberty and menarche are reported (1). The two isoenzymes of 3β-hydroxysteroid dehydrogenase are coded by two highly homologous genes called HSD3B1 and HSD3B2. 3β-hydroxysteroid dehydrogenase deficiency is only caused by mutations of the HSD3B2 gene. The severity of the salt-loss depends on the residual activity of the mutant enzyme. No such relationship can be seen with the degree of under-virilization in genetic males. Patients suffering from 3β-hydroxysteroid dehydrogenase type II deficiency need glucocorticoid and mineralocorticoid therapy. Depending on the residual activity of the mutant enzyme the pubertal development has to be initiated, and supported with oestrogens and progestogens. Micropenis in genetic males can be treated with local application of dihydrotestosterone during infancy. Operative repair of hypospadias should be performed within the first year of life.

17α-hydroxylase/17,20-lyase deficiency is a rare type of steroidogenic disease (45). Most cases are found in consanguineous families. The enzyme 17α-hydroxylase/17,20-lyase converts pregnenolone into 17-hydroxypregnenolone and progesterone into 17-hydroxyprogesterone by its hydroxylase activity. The same enzyme promotes a 17,20-lyase reaction in order to build DHEA and androstenedione out of 17-hydroxypregnenolone and 17-hydroxyprogesterone. Hence, deficient 17α-hydroxylase activity causes a deficiency of glucocorticoids, as well as sex steroids (2). Glucocorticoid deficiency causes an increase in ACTH secretion, which in turn leads to elevated precursor steroids with mineralocorticoid activity and, hence, hypertension. As corticosterone binds to the glucocorticoid receptor, the patients are usually not in danger of having adrenal crisis. Rare cases of isolated 17,20-lyase deficiency have been described, showing isolated absence of sex steroids. Girls with classical 17α-hydroxylase deficiency are born with normal external and internal genitalia. Genetic males show a disorder of sex development, most often a complete sex reversal. However, müllerian structures are absent in these cases. Both sexes clinically manifest with primary amenorrhoea and absent signs of puberty. In case of partial enzyme inactivation some breast development might be seen. The elevated mineralocorticoid precursors are responsible for increased blood pressure, low potassium, and suppressed renin levels. Patients with the isolated 17,20-lyase deficiency present with lack of pubertal development without glucocorticoid deficiency or hypertension. The deficiency of sex steroid causes elevated levels for luteinizing hormone and follicle-stimulating hormone (FSH) around the time of puberty consistent with hypergonadotropic hypogonadism. Inactivating mutations within the CYP17A1 gene are responsible for both clinical forms. The protein is a type II P450 enzyme, using NADPH as co-factor and P450 oxidoreductase and cytochrome b5 as electron donators (18). Approximately 30 mutations have been described, which usually completely inactivate enzymatic activity. In contrast, mutations responsible for isolated 17, 20-lyase deficiency impede cytochrome b5 binding, which is essential for the generation of DHEA and androstenedione, but not for 17α-hydroxylase activity. Therapy aims at normalizing glucocorticoid levels in order to lower ACTH levels and, hence, reduce mineralocorticoid precursors and blood pressure. As with other forms of CAH, hydrocortisone is the preferred treatment when a child is growing. Thereafter, therapy may be switched to prednisone or dexamethasone. Depending on the age at start of treatment glucocorticoids may or may not normalize the blood pressure. Most patients with 17α-hydroxylase deficiency are raised as females. As the diagnosis is usually made during adolescence, gonadectomy should be discussed in genetic males. Both sexes typically need induction of puberty with estrogens.

Oxidoreductase deficiency is a combined lesion affecting 21-hydroxylase and 17α-hydroxylase activity. It is caused by inactivating mutations within the POR gene located on chromosome 7 (15). P450 oxidoreductase is the electron donator for class II P450 enzymes, namely adrenal 21-hydroxylase and 17α-hydroxylase. Oxidoreductase deficiency is associated with slightly elevated levels of 17-hydroxyprogesterone and progesterone together with low levels of sex steroids, but normal mineralocorticoid biosynthesis. Insufficient levels of sex steroids lead to under-virilization in genetic males (31). Interestingly, genetic females show some virilization of the external genitalia. In addition, hyperandrogenaemia may be noticed in the pregnant mother causing acne or hirsutism. No further virilization is noticed after birth in female offspring. The male under-virilization is most likely caused by insufficient DHEA production. However, the prenatal virilization in females is at present explained by an alternative pathway for androgen biosynthesis, which is active during pregnancy, but inactive thereafter. Reports on pubertal development in oxidoreductase deficiency are scarce. It can expected that puberty will need to be induced and supported in both sexes. Basal glucocorticoid biosynthesis is usually adequate for survival. However, because of a high likelihood for stress intolerance of the adrenal, increased stress dosing with glucocorticoids is advisable. In addition to the adrenal phenotype, sterol biosynthesis is altered due to a reduced 14α-demethylase activity due to oxidoreductase deficiency. The altered sterol formation is most likely responsible for the skeletal phenotype in oxidoreductase deficiency. Signs of the disease are craniofacial dysmorphism with low-set ears, mid-facial hypoplasia, craniosynostosis, choanal atresia, arachnodactyly, and radiohumeral synostosis (35).

Increased adrenal androgen biosynthesis causing severe forms of disorders of sex development is present in 11β-hydroxylase deficiency. Minor virilization of 46,XX individuals can be seen in 3β-hydroxysteroid dehydrogenase type II deficiency and P450 oxidoreductase deficiency. These two entities are discussed above.

Adrenal 11β-hydroxylase converts 11-deoxycortisol into cortisol. Therefore, 11β-hydroxylase deficiency causes cortisol deficiency with concomitant ACTH increase and adrenal hyperplasia. The steroid precursors are shunted into adrenal androgen production causing prenatal and postnatal virilization. The enzyme 11β-hydroxylase can also convert 11-deoxycorticosterone into corticosterone. Metabolites such as 19-nor-deoxycorticosterone synthesized with 11β-hydroxylase deficiency cause the clinical picture of hypertension. Classical 11β-hydroxylase deficiency is the second most common type of congenital adrenal hyperplasia (46). The incidence is approximately 1:200,000 in Europe although the exact frequency is dependent on the population background. Nonclassical forms of 11β-hydroxylase deficiency are described. Classic and nonclassical forms are recognized. Classical forms show the potential for prenatal virilization, which is comparable to virilization in 21-hydroxylase deficiency. Genetic females have normal internal genitalia and should be raised as females. The male genitalia are normal at birth. Persistent androgen excess causes increased growth velocity, advanced bone maturation resulting in reduced adult height. Boys develop isosexual precocious pseudopuberty and girls present with heterosexual precocious pseudopuberty, which will subsequently turn into central precocious puberty. In 11β-hydroxylase deficiency salt loss does not occur as 11-deoxycorticosterone and other metabolites act as mineralocorticoids and adrenal crises are not typically seen as corticosterone can act on the glucocorticoid receptor. However, these precursors are not directly regulated by ACTH and, therefore, biosynthesis is not increased by additional stressors. Female patients with nonclassical 11β-hydroxylase deficiency present without severe prenatal virilization. Some cases with isolated cliteromegaly have been reported. Both sexes develop symptoms of hyperandrogenaemia, such as increased height velocity, premature pubarche, hirsutism, or acne. The clinical picture is therefore comparable to nonclassic 21-hydroxylase deficiency. A plasma sample is sufficient to diagnose classical 11β-hydroxylase deficiency. The precursors 11-deoxycorticosterone and 11-deoxycortisol are highly elevated. Cortisol is below normal and ACTH is elevated. Renin is suppressed because of the mineralocorticoid action of 11-deoxycorticosterone. 11β-hydroxylase deficiency may be detected indirectly in newborn screening by slightly elevated levels of 17-hydroxyprogesterone. As with nonclassical 21-hydroxylase deficiency, the nonclassical form of 11β-hydroxylase deficiency has to be diagnosed by ACTH stimulation testing. The enzyme 11β-hydroxylase is coded by the CYP11B1 gene. It is located on chromosome 8q24 in close proximity to the highly homologous CYP11B2 gene coding aldosterone synthase. Mutations in the CYP11B1 cause 11β-hydroxylase deficiency (43). The disease follows a recessive trait. Mutations causing classic 11β-hydroxylase deficiency have no residual enzyme activity. Mutations such as N133H, T319M, or P42S have some residual activity and cause nonclassical 11β-hydroxylase deficiency. Like other forms of CAH, 11β-hydroxylase is treated with glucocorticoids to suppress adrenal androgen production, and to lower the elevated mineralocorticoid precursors and the blood pressure. Hydrocortisone is the recommended glucocorticoid during childhood and adolescence. Stress dosing with hydrocortisone is advised in cases of intercurrent illness, fever, and operations. Virilized genetic females should undergo feminizing surgery. Fertility can be normal with adequate treatment. Prenatal therapy with dexamethasone can reduce or prevent prenatal virilization (8). However, the same limitations and uncertainties are present as encountered with prenatal therapy in 21-hydroxylase deficiency.