Thyroid hormones and male reproductive system

Experimental hypothyroidism during sexual development Testes size and number of spermatozoa in adulthood are determined by postnatal/pubertal proliferation of seminal tubule somatic cell constituents, the Sertoli cells. Cessation of proliferation of Sertoli cells during early development occurs concomitantly with formation of their terminally differentiated population. Transient experimental hypothyroidism in newborn rats evokes prolongation of Sertoli cell proliferation period and retards their maturation. In adulthood it results in increased Sertoli cell number, doubled final testis size in comparison to normal values, and animals produce more spermatozoa. However, prolonged hypothyroidism depresses testicular development and induces germ cell degeneration.