Endocrine Abstracts (2006) 11 P912

Is 131I therapy for hyperthyroidism harmful for testis function?

C Ceccarelli, D Canale, E Fiore, C Moschini, C Caglieresi, P Vitti & A Pinchera

Dept. of Endocrinology - University of Pisa, Pisa, Italy.

Radioiodine-131 is commonly used for treatment of hyperthyroidism, however the effects on testis function are not known. This prompted us to study testis function in hyperthyroid men after 131I treatment. 15 hyperthyroid patients scheduled for 131I treatment underwent: testis US, hormone assessment and sperm analysis before and 45 days, 3, 6 and 10–15 months after 131I. The control group (for testis volume and semen analysis) was constituted by 19 normal subjects. Testis volume was similar in patients and in controls (31 and 32 ml, respectiveliy). Basal hormone levels in hyperthyroid males were within the normal limit.

After 131I treatment, FSH did not change significantly. Only in 2 patients FSH increased: one of them was severely hyperthyroid and underwent a second course of 131I; the other had small testes and basal FSH in the normal upper limit. Serum testosterone and testosterone/LH (T/LH) ratio were significantly reduced as compared to basal values from 45 days to 6 months after treatment and reverted to basal levels after one year. Semen analysis showed sperm concentration and percentage of normal form not different between patients and controls. Motility was significantly reduced (P=0.008). 10 out of 15 hyperthyroid patients (67%) were asthenospermic before treatment. No significant variation of sperm concentration and percentage of normal forms was observed after 131I. On the contrary, a significant increase of progressive motility was observed after 131I therapy (P=0.01).

Conclusions: Our results show that in males treated for hyperthyroidism with 131I, germinal epithelium and Leydig cell function undergo only marginal changes that might have some relevance in subjects with a pre-existing fertility impairment.

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