Gonads

• Klinefelter's syndrome


  • Occurs in about 1 of 400 men and is caused by the presence of an extra X chromosome (47 chromosomes, XXY sex chromosomes)
  • Due to the presence of Barr bodies → "extra/inactive" X chromosome
  • Pregnancies have been reported in this condition
  • Characterized by: gynecomastia, presence of small and firm testicles, smaller penis, taller less muscular body, weaker bones, lower energy level, delay in puberty, less facial and body hair, broader hips and longer legs, azoospermia and resultant sterility, low testosterone levels but high FSH and LH levels
  • Low testosterone can be caused by deficient seminiferous tubule mass
  • High FSH (due to underproduction of inhibin) and LH levels induce increased aromatase activity, resulting in elevated estrogen levels
• Testicular feminization syndrome


  • Most severe form of androgen resistance syndrome, resulting from mutation of the androgen receptor and lack of testosterone action in the target tissues
  • The physical development of a patient pursues the female phenotype, with fully developed breast and female distribution of fat and hair
  • Biochemical evaluation reveals normal levels of testosterone with elevated FSH and LH levels
• Monitoring Testosterone Replacement Therapy

  1. Prostate-specific antigen (PSA), blood counts, and lipid levels should be checked 3–6 months after initiation of testosterone replacement and at least yearly thereafter

  2. If PSA elevation is noted after testosterone replacement, prostate evaluation with possible biopsy is recommended

  3. Active prostate cancer is a contraindication to testosterone replacement
• Regulation of Female Reproduction

  1. Before the onset of puberty, both LH and FSH are secreted in small amounts, but as puberty approaches, the amplitude of LH and FSH pulsatile secretions increases and nocturnal rise in LH secretion increases

  2. Nocturnal rise disappears with adulthood

  3. Onset of puberty is characterized by increasing secretion of LH and FSH that stimulates gonadal activity and increased activity of hypothalamic GnRH neurons