Hypogonadism

Hypogonadism is a medical term for a defect of the reproductive system that 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.

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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 that 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 and in athletes using AAS illicitly.

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

Symptoms

Low Testosterone (Low T) symptoms include loss of energy, fatigue, loss of libido, muscle mass decline, decreased positive mood factors and an increased negative mood factors.

Diagnosis

Low Testosterone can be identified through a simple blood test performed by a physician. Normal testosterone levels range from 298 - 1098 ng/dl. Physicians measure gonadotropins (LH and FSH) to distinguish primary from secondary hypogonadism. In primary hypogonadism the LH and/or FSH are usually elevated, whereas, 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, wherein reproductive function is termed constitutional delay.

Treatment

Hypogonadism is most often treated by replacement of the appropriate hormones. For men, this is testosterone. Commonly-used testosterone formulations include transdermal testosterone, injectable testosterone, and buccal testosterone. Oral testosterone is no longer used in the U.S. because it is broken down in the liver and rendered inactive. Another feasible alternative is human chorionic gonadotropin (hCG). For women estradiol and progesterone are replaced. Some types of fertility defects can be treated; some cannot.

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