Effect of thyroid hormone on the pre- and post-natal development of the rat testis

The relationship between thyroid function and testicular development in the rat was investigated. Hypothyroidism was induced during fetal or postnatal life by adding methimazole (MMI) to the drinking water of pregnant or lactating mothers. A group of newborn rats was treated with MMI and i.p. injections of L-tri-iodothyronine (L-T 3 ). Hypothyroidism was shown by the reduced serum levels of total T 3 and of total thyroxine (T 4 ) in pregnant mothers and in pubertal rats.