Key Points
2
➤ Hypogonadism is a clinical syndrome that results from failure of
the testis to produce physiological concentrations of testosterone
(T deficiency) and/or a normal number of spermatozoa due to
pathology at one or more concentrations of the hypothalamic-
pituitary-testicular axis.
➤ Testosterone (T) deficiency can be due to testicular defects
(primary hypogonadism), hypothalamus-pituitary defects (secondary
hypogonadism) or both.
• Primary hypogonadism results in low T concentrations, impairment of
spermatogenesis, and elevated gonadotropin levels. The causes of primary
hypogonadism are listed in Table 1.
• Secondary hypogonadism results in low T concentrations, impairment of
spermatogenesis, and low or inappropriately normal gonadotropin levels. Causes
of secondary hypogonadism are listed in Table 1.
• Combined primary and secondary hypogonadism results in low T concentrations,
impairment of spermatogenesis, and variable gonadotropin levels.
➤ Additionally, the process of evaluating secondary hypogonadism
may uncover a deficiency/excess of other pituitary hormones or a
hypothalamic or pituitary tumor that may require management in
addition to treating hypogonadism.
