Hypogonadism means diminished functional activity of the gonads—the testes or the ovaries—that may result in diminished production of sex hormones. Low androgen (e.g., testosterone) levels are referred to as hypoandrogenism and low estrogen (e.g., estradiol) as hypoestrogenism. These are responsible for the observed signs and symptoms in both males and females. Hypogonadism, commonly referred to by the symptom "low testosterone" or "Low T", can also decrease other hormones secreted by the gonads including progesterone, DHEA, anti-Müllerian hormone, activin, and inhibin. Sperm development (spermatogenesis) and release of the egg from the ovaries (ovulation) may be impaired by hypogonadism, which, depending on the degree of severity, may result in partial or complete infertility. In January 2020, the American College of Physicians issued clinical guidelines for testosterone treatment in adult men with age-related low levels of testosterone. The guidelines are supported by the American Academy of Family Physicians. The guidelines include patient discussions regarding testosterone treatment for sexual dysfunction; annual patient evaluation regarding possible notable improvement and, if none, to discontinue testosterone treatment; physicians should consider intramuscular treatments, rather than transdermal treatments, due to costs and since the effectiveness and harm of either method is similar; and, testosterone treatment for reasons other than possible improvement of sexual dysfunction may not be recommended. Classification
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 usually means 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 (hyper-gonatropic hypogonadism); whereas in secondary hypogonadism, both are normal or low, suggesting the problem is in the brain (hypo-gonatropic hypogonadism). Affected system
Hypogonadism resulting from defects of the gonads is referred to as hypergonadotropic hypogonadism or 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 is termed hypogonadotropic hypogonadism (HH), secondary hypogonadism, or central hypogonadism (referring to the central nervous system).Examples of hypothalamic defects include Kallmann syndrome. Examples of pituitary defects include hypopituitarism and pituitary hypoplasia. 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 varying clinical phenotypes of sexual characteristics despite XY chromosomes.