Effects of treatment with radioiodine (¹³¹I) on the gonadal function of the hyperthyroid patients

Introduction: Hyperthyroidism is a relatively common disorder caused by different etiologies. Graves’ disease, and toxic-nodular goiter (Plummer’s disease) are among the most common causes. Treatment with radioiodine is considered to be the treatment of choice in many of the patients. Higher biological half-life of ¹³¹I in hyperthyroid patients as compared with patients with differentiated thyroid carcinoma who have undergone thyroidectomy, may lead to a higher frequency of complications with radioiodine at similar dosage. Therefore gonadal dysfunction in hyperthyroid patients treated with radioactive iodine is not unlikely. Material and Methods: Hyperthyroid patients with the clinical diagnosis of Graves’ disease, toxic multinodular goiter and toxic adenoma were entered the study. Their age distribution was 16-40 years in women and 17-60 years in men (Reproductive years). Patients were euthyroid at the time of radioiodine treatment. FSH, LH, testosterone and semen analysis in men; and FSH, LH, estrogen and progesterone in women were measured before and 3 months after radioiodine therapy. All patients with previous history of radioiodine treatment, those with known sexual hormone abnormalities, women with a history of tube ligation and men with a history of vasectomy, as well as those women who were receiving OCP contraception were excluded from the study. Results: From 104 enrolled patients, 40 (38.5%) were men and 64 (61.5%) were women. The cause of hyperthyroidism was Graves’ disease in 66 cases (63.5%), toxic multinodular goiter in 28 cases (26.9%) and toxic adenoma in 10 others (9.6%). Hormonal status was normal in all patients before therapy while this became abnormal in 20 (19.2%) of patients after treatment. Semen analysis became abnormal in 8/20 (40%) of the patients after treatment. Conclusion: Among different variables which were analyzed during study, meaningful correlation was found in the following situations: FSH values in men and women were found to be increased after radioiodine treatment (P35) (P=0.003) and changes in hormonal status in women in two different age groups (=30) were found to be statistically significant (P=0.015).