Hypogonadism

Hypogonadism is a medical term for a defect of the reproductive system which results in lack of function of the gonads (ovaries or testes). The gonads have two functions: to produce hormones (testosterone, estradiol, antimullerian hormone, progesterone, inhibin B), activin and to produce gametes (eggs or sperm). 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.

Classification
There are many possible types of hypogonadism and several ways to categorize them.

by Congenital vs. acquired

 * An example of congenital hypogonadism (present at birth) is Turner syndrome.
 * An example of acquired hypogonadism (develops in childhood or adult life) is castration.

by Hormones vs. fertility
Hypogonadism can involve just hormone production or just fertility, but most commonly involves both.
 * Examples of hypogonadism that affect hormone production more than fertility are hypopituitarism and Kallmann syndrome; in both cases fertility is reduced until hormones are replaced but can be achieved solely with hormone replacement.
 * Examples of hypogonadism that affect fertility more than hormone production are Klinefelter syndrome and Kartagener syndrome.

by Affected system
Hypogonadism is also categorized by endocrinologists by the level of the reproductive system which is defective.


 * Hypogonadism resulting from defects of the gonads is traditionally referred to as primary hypogonadism. Examples include Klinefelter syndrome and Turner syndrome.


 * 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 hormone response is androgen insensitivity syndrome

Steroid use
Hypogonadism may be induced by chronic use of anabolic/androgenic steroids (AAS). The negative-feedback system of the hypothalamic-pituitary-gonadal axis (HPTA) shuts down pituitary production of gonadotropins after extended exposure to AAS. This has been documented both in patients receiving AAS for legitimate medical reasons such as AIDS or cancer as well as athletes using AAS illicitly.

Hypogonadism may persist for some time after steroid use is discontinued.

Diagnosis
Physicians measure gonadotropins (LH and FSH) to distinguish primary from secondary hypogonadism. In primary hypogonadism the LH and/or FSH are usually elevated, while in secondary hypogonadism both are normal or low.

Hypogonadism is often discovered during evaluation of delayed puberty, but ordinary delay which eventually results in normal pubertal development and reproductive function is termed constitutional delay.

Treatment
Hypogonadism is most often treated by replacement of the appropriate hormones. For men this is testosterone. For women estradiol and progesterone are replaced. Some types of fertility defects can be treated; some cannot.