Hypogonadism is a medical term which describes a diminished functional activity of the gonads – the testes and ovaries in males and females, respectively – that may result in diminished sex hormone biosynthesis and impaired gamete production and/or regulation. Low androgen (e.g., testosterone) levels are referred to as hypoandrogenism and low estrogen (e.g., estradiol) as hypoestrogenism, and may occur as symptoms of hypogonadism in both sexes, but are generally only diagnosed in males and females respectively. Other hormones produced by the gonads which may be decreased by hypogonadism include progesterone, DHEA, anti-Müllerian hormone, activin, and inhibin. Spermatogenesis and ovulation in males and females, respectively, may be impaired by hypogonadism, which, depending on the degree of severity, may result in partial or complete infertility.
Contents

1 Classification 1.1 Affected system 1.2 Primary or secondary 1.3 Congenital vs. acquired 1.4 Hormones vs. fertility 2 Symptoms 2.1 In both sexes 2.2 Exclusively in men 2.3 Exclusively in women 3 Diagnosis 3.1 In men 3.2 In women 4 Treatment 5 Testosterone and longevity 6 See also 7 References 8 External links

Classification
Main article: Hypergonadotropic hypogonadism
Main article: Hypogonadotropic hypogonadism
Main article: Isolated hypogonadotropic hypogonadism

Deficiency of sex hormones can result in defective primary or secondary sexual development, or withdrawal effects (e.g., premature menopause) in adults. Defective egg or sperm development results in infertility. The term hypogonadism is usually applied to permanent rather than transient or reversible defects, and usually implies deficiency of reproductive hormones, with or without fertility defects. The term is less commonly used for infertility without hormone deficiency. There are many possible types of hypogonadism and several ways to categorize them. Hypogonadism is also categorized by endocrinologists by the level of the reproductive system that is defective. Physicians measure gonadotropins (LH and FSH) to distinguish primary from secondary hypogonadism. In primary hypogonadism the LH and/or FSH are usually elevated, meaning the problem is in the testicles, whereas in secondary hypogonadism, both are normal or low, suggesting the problem is in the brain.
Affected system

Hypogonadism resulting from defects of the gonads is traditionally referred to as primary hypogonadism. Examples include Klinefelter syndrome and Turner syndrome. Mumps is known to cause testicular failure, and in recent years has been immunized against in the US. A varicocele can reduce hormonal production as well.

Hypogonadism resulting from hypothalamic or pituitary defects are termed secondary hypogonadism or central hypogonadism (referring to the central nervous system). Examples of Hypothalamic defects include Kallmann syndrome. Examples of Pituitary defects include hypopituitarism.

An example of a hypogonadism resulting from the lack of hormone response is androgen insensitivity syndrome, where there are inadequate receptors to bind the testosterone, resulting in a female appearance despite XY chromosomes.