Learning Objective

Understand how androgens influence muscle mass, the temperature-dependent process of spermatogenesis, and the regulation of FSH and LH secretion in males.

Effect on Muscle Mass

The capacity of androgens to stimulate protein synthesis and decrease protein breakdown, especially in muscle, is responsible for the larger muscle mass in men compared with women.
Exogenous androgens (anabolic steroids) are sometimes taken by men and women in an attempt to increase muscle mass. Excess use can lead to adverse effects.

Spermatogenesis Is Temperature-Dependent

Effect on Fertility: Spermatogenesis ceases at temperatures typical of the abdominal cavity. If the testes fail to descend (a condition called cryptorchidism) and surgical correction is not performed, infertility results.

Normally, the scrotum provides an environment approximately 4°C cooler than the abdominal cavity. This cooling is achieved by a countercurrent heat exchanger in the spermatic cord. The temperature of the scrotum and testes is also regulated by the contraction and relaxation of the cremasteric muscles and scrotal skin rugae that surround and suspend the testes.

Activity

Effect on FSH and LH

Elevated temperatures of cryptorchid testes adversely affect Sertoli cells and germ cell maturation. In adults with bilaterally undescended testes:

• FSH secretion is elevated, likely due to decreased inhibin production by Sertoli cells.
• Testosterone secretion by Leydig cells is low, resulting in elevated LH secretion.

Clinical relevance: Cryptorchidism in adulthood leads to impaired spermatogenesis and hormonal imbalances, highlighting the importance of early surgical correction.

Activity