Pituitary GH and prolactin deficiency and testis enlargement in hypothyroid rats caused by goitrogen methimazole.

This paper describes the effects of goitrogen-induced hypothyroidism on GH, prolactin and the testis size of rats. Hypothyroidism was caused by lifetime-rearing on goitrogen methimazole (MMI). This condition was brought on by adding 0.025% (Weight/ Volume) MMI to the mother's drinking water immediately after birth. Offspring, after weaning, were given the same food and drinking water as that of the mother until sacrified. Four experimental groups were designed: group 1, CMF (normal rat chow) and tap water; group 2, CMF with 0.025% thyroid powder and tap water; group 3, CMF and tap water containing 0.025% MMI and group 4, CMF with the thyroid powder and tap water containing 0.025% MMI. The rats were killed at 73 days of age after rearing under the 4 conditions described. Pituitary GH and PRL and serum PRL were significantly less in group 3 than in the others. Testis weight was the same for groups 3 (2.51 +/- 0.14 g; Mean +/- SD), 1 (2.76 +/- 0.07 g) and 2 (2.60 +/- 0.06 g). Increased testis weight was noted only in group 4 (3.25 +/- 0.1 g). The ratio of testis to body weight was significantly higher in group 3 than in the other groups. The authors concluded that hypothyroidism causes pituitary dysfunction with GH and PRL deficiency and also causes testis enlargement with age.