Hypogonadism

• 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).[3]
  • 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.[4]
  • Isolated hypogonadotropic hypogonadism (IHH), also called idiopathic or congenital hypogonadotropic hypogonadism (CHH) as well as isolated or congenital gonadotropin-releasing hormone deficiency (IGD) accounts for a small subset of cases of hypogonadotropic hypogonadism (HH) due to deficiency in or insensitivity to gonadotropin-releasing hormone (GnRH) where the function and anatomy of the anterior pituitary are otherwise normal and secondary causes of HH are not present.

• Primary - defect is inherent within the gonad: e.g. Noonan syndrome, Turner syndrome (45X,0), Klinefelter syndrome (47XXY), XY with SRY gene-immunity[5]
• Secondary - defect lies outside of the gonad: e.g. Polycystic ovary syndrome, and Kallmann syndrome, also called hypogonadotropic hypogonadism.[6] Hemochromatosis and diabetes mellitus can be causes of this as well.[7]

• Examples of congenital causes of hypogonadism, that is, causes that are present at birth:
  • Turner syndrome and Klinefelter syndrome. It is also one of the signs of CHARGE syndrome.
• Examples of acquired causes of hypogonadism:
  • Opioid Induced Androgen Deficiency (resulting from the prolonged use of opioid class drugs, e.g. codeine, Dihydrocodeine, morphine, oxycodone, methadone, fentanyl, hydromorphone, etc.)
  • Anabolic steroid-induced hypogonadism (ASIH)
  • Childhood mumps
  • Children born to mothers who had ingested the endocrine disruptor diethylstilbestrol for potential miscarriage
  • Traumatic brain injury, even in childhood
  • In males, normal aging causes a decrease in androgens, which is sometimes called "male menopause" (also known by the coinage "manopause"), late-onset hypogonadism (LOH), and "andropause" or androgen decline in the aging male (ADAM), among other names.
  • It is a symptom of hereditary hemochromatosis[8]

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.

Hypogonadism can occur in other conditions, like Prader–Willi syndrome.

The symptoms of hypogonadotrophic hypogonadism, a subtype of hypogonadism, include late, incomplete or lack of development at puberty, and sometimes short stature or the inability to smell; in females, a lack of breasts and menstrual periods, and in males a lack of sexual development, e.g., facial hair, penis and testes enlargement, deepening voice.

Testing serum LH and FSH levels are often used to assess hypogonadism in women, particularly when menopause is believed to be happening. These levels change during a woman's normal menstrual cycle, so the history of having ceased menstruation coupled with high levels aids the diagnosis of being menopausal. Commonly, the post-menopausal woman is not called hypogonadal if she is of typical menopausal age. Contrast with a young woman or teen, who would have hypogonadism rather than menopause. This is because hypogonadism is an abnormality, whereas menopause is a normal change in hormone levels. In any case, the LH and FSH levels will rise in cases of primary hypogonadism or menopause, while they will be low in women with secondary or tertiary hypogonadism.[10]

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. It may be discovered during an infertility evaluation in either men or women.[11]

Low testosterone can be identified through a simple blood test performed by a laboratory, ordered by a health care provider. Blood for the test must be taken in the morning hours, when levels are highest, as levels can drop by as much as 13% during the day and all normal reference ranges are based on morning levels.[12] However, low testosterone in the absence of any symptoms does not clearly need to be treated.

Normal total testosterone levels depend on the man's age but generally range from 240 to 950 ng/dL (nanograms per deciliter) or 8.3-32.9 nmol/L (nanomoles per liter).[13] According to American Urological Association, the diagnosis of low testosterone can be supported when the total testosterone level is below 300 ng/dl.[14] Some men with normal total testosterone have low free or bioavailable testosterone levels which could still account for their symptoms. Men with low serum testosterone levels should have other hormones checked, particularly luteinizing hormone to help determine why their testosterone levels are low and help choose the most appropriate treatment (most notably, testosterone is usually not appropriate for secondary or tertiary forms of male hypogonadism, in which the LH levels are usually reduced).

Treatment is often prescribed for total testosterone levels below 230 ng/dL with symptoms.[15] If the serum total testosterone level is between 230 and 350 ng/dL, free or bioavailable testosterone should be checked as they are frequently low when the total is marginal.

The standard range given is based on widely varying ages and, given that testosterone levels naturally decrease as humans age, age-group specific averages should be taken into consideration when discussing treatment between doctor and patient.[16] In men, testosterone falls approximately 1 to 3 percent each year.[17]

Blood testing

A position statement by the Endocrine Society expressed dissatisfaction with most assays for total, free, and bioavailable testosterone.[18] In particular, research has questioned the validity of commonly administered assays of free testosterone by radioimmunoassay.[18] The free androgen index, essentially a calculation based on total testosterone and sex hormone-binding globulin levels, has been found to be the worst predictor of free testosterone levels and should not be used.[19] Measurement by equilibrium dialysis or mass spectroscopy is generally required for accurate results, particularly for free testosterone which is normally present in very small concentrations.