Androgens: Male sex hormones.

The amount of these estrogens in the body varies over the course of the menstrual cycle. After menopause, estrone becomes the predominant endogenous estrogen in women’s bodies even though the ovaries continue to produce small amounts of estradiol, as do the secondary hormone-production sites. The adrenal gland continues to produce androstenedione, which is converted to estrone and estradiol in body fat and in muscle and skin cells. In addition, the ovaries continue making small amounts of testosterone, which can be converted to estradiol.

  • The brain regulates almost all aspects of reproductive life, from the development of the sex organs to their ultimate aging
  • Puberty is a brain-driven event, initiated even in the absence of gonads
  • Gonadotropins from brain and hypothalamus have a critical role in establishing and maintaining normal sexual activity
  • Hypothalamus passes gonadotropin releasing hormone to anterior pituitary and triggers secretion of two gonadotropins
    1. Luteinizing hormone (LH): manufacture of testosterone
    2. Follicle-stimulating hormone (FSH): sperm production
  • Gonadotropin releasing hormone levels decline with aging


Male Secondary Sexual Characteristics

Testosterone levels are low for the first decade; The onset of puberty is brain driven.
  • Triggered by surge in testosterone production; results in onset of sperm production
  • Sexual organs grow and develop
  • Voice changes; muscle and bone growth