Plasma Glycoprotein Hormone α-Subunit in the Syndrome of Gonadal Dysgenesis: The Effect of Estrogen Replacement in Hypergonadotropic Hypogonadism^*

Elevated plasma LH and FSH levels in hypergonadotropic hypogonadism can be reduced byestrogen therapy, but the change in readily releasable glycoprotein hormone α-subunit with therapy is undefined. We administered 100 μg LRF iv to seven patients (11–19 yr old)with the syndrome of gonadal dysgenesis before and during 9 months of therapy with oral conjugatedestrogens at a dose of 0.3 mg/day. The control group was seven normal girls, aged 12–16 yr. Mean basal glycoprotein hormone levels for the untreated and treated gonadal dysgenesis groups and the control group were, respectively: α-subunit, 4.2, 1.3, and 0.8 ng/ml; LH, 9.3, 3.3, and 1.4 ng/ml; and FSH, 46.7, 17.8, and 1.6 ng/ml. Mean peak LRF-stimulated values for the untreated and treated gonadal dysgenesis groups and the control group were, respectively: α-subunit, 18.9, 5.1, and 3.7 ng/ml; LH, 43.4, 11.8, and 6.4 ng/ml; and FSH, 78.0, 23.3, and 3.6 ng/ml. Mean basal and peak plasma α-subunit, LH, andFSH concentrations in untreated patients with gonadal dysgenesis were higher (P < 0.005) than those in controls and treated patients (P < 0.05). The mean basal and peak plasma α-subunit and LH concentrations in treated patients were not significantly different than those in control patients. Mean basal and peak FSH concentrations in treated patients with gonadal dysgenesis were significantly higher (P < 0.05) than those in the control group.

We conclude that 1) basal and peak LRF-stimulated plasma α-subunit values are significantly higher in untreated patients with gonadal dysgenesis than in normal girls and low dose estrogen therapy decreases α-subunit concentrations to normal; 2) estrogen therapy lowers basal and LRF-stimulated plasma LH concentrations to the normal range and lowers basal and LRF-stimulated FSH concentrations to a lesser degree; and 3) the release of the α-subunit in patients without primary thyroid disease is stimulated by hypothalamic LRF, as are the gonadotropins, but the secretion of α-subunit is more closely associated with the secretion of human LH than with that of human FSH.