(1) The principal androgenic hormone, produced by the interstitial (Leydig) cells of the testes in response to stimulation by the luteinizing hormone of the anterior pituitary gland; it is thought to be responsible for regulation of gonadotropic secretion, spermatogenesis, and wolffian duct differentiation. It is also responsible for other male characteristics after its conversion to dihydrotestosterone. In addition, testosterone possesses protein anabolic properties. It is used as replacement therapy for androgen deficiency in males, in the treatment of delayed male puberty or hypogonadism, and in the palliation of certain breast cancers in females; used as the base or various esters (e.g., cypionate, enanthate, propionate).
(2) Tthe most important male sex hormone (androgen) produced by the Leydig cells of the testes in response to luteinizing hormone (LH) secreted by the pituitary. Its chief function is to stimulate the development of the male reproductive organs and the secondary sex characters, such as the crest. It is necessary for the appearance of normal male sexual behavior. It encourages growth of bone and muscle, and helps maintain muscle strength. It is occasionally secreted in large amounts also by granulosa-theca cell tumors of the ovary, especially in mares.