Inhibitory effects of hypothyroidism on the testicular functions of postnatal rats

The effects of thyroid hormones on female gonadal functions are well established. The role of thyroid hormones in testicular physiology is still uncertain, and so the effect of hypothyroidism on the testicular functions was investigated in postnatal rats. Hypothyroidism was induced during postnatal life by adding methimazole to the drinking water of lactating mothers starting from the day of birth. On day 25 the rats were sacrificed and testis, epididymis, seminal vesicles and ventral prostate were collected. A reduction in the body weight and the weights of testis, epididymis and accessory sex organs of treated rats was recorded. The levels of all the biochemical parameters in the testis, e.g. protein, RNA, ascorbic acid, acid phosphatase, alkaline phosphatase and isocitrate dehydrogenase, were reduced following methimazole treatment. The results indicated decreased bioavailability of androgens in hypothyroid rats and an inhibition of testicular functions. The results suggest that thyroid hormones are necessary for normal testicular functions.