Thyroid nodules

Neck XRT or TBI

Malignant nodules

Benign nodules

Significant increased risk following neck XRT (RR ∼15)

Incidence increases from 5–10 years post XRT

Possible ‘cell kill’ effect at doses above 30 Gy

Risk significantly greater in children compared with adults, and females compared with males

Increased prevalence of all benign thyroid disease

Palpable nodules in 20–30% patients who received neck XRT

Prevalence dependent on time since XRT, female gender, and XRT dose

Thyroid dysfunction

Neck XRT or TBI

Hypothyroidism

Hyperthyroidism

Frank or compensated hypothyroidism occurs in 20–30% of patients who receive TBI, and 30–50% of those who received neck irradiation (30–50 Gy)

Hypothyroidism generally occurs within 5 years of XRT

Thyroxine therapy should be instituted early because of the hypothesis that an elevated TSH may drive early thyroid cancers

Graves’ disease is reported to occur at increased frequency (RR ∼8)

Parathyroid

Neck XRT

Late-onset hyperparathyroidism

Latency of 25–47 years

Dose-dependency observed