Hypogonadism

Clinical information

Hypogonadism occurs when the body's sex glands, also called gonads (ovaries or testes), produce little or no sex hormones. Hypogonadism can also cause a reduction in the levels of other hormones produced in the gonads such as dehydroepiandrosterone (DHEA), progesterone and anti-Müllerian hormone (AMH).

The cause of hypogonadism can be primary (due to a problem with the testes or ovaries) or secondary (hypogonadotropic hypogonadism), which is caused by a lack of the hormones released by the pituitary gland or hypothalamus that normally stimulate the gonads.

Male hypogonadism is defined as a failure of testicular function that affects androgen production, sperm production or both. A decline in testosterone levels occurs naturally with ageing from the age of 30, with an estimated 20 % of men over 60 and 30 % to 40 % over 80 having subnormal testosterone levels. A decrease in testosterone levels can also occur as a result of acute or chronic illness, depression or wasting conditions. Disorders affecting the hypothalamic–pituitary–testicular axis can also lead to hypogonadism. In addition to ageing, other risk factors for developing hypogonadism include poor diet, obesity and type II diabetes.

The clinical features of female hypogonadism depend on the age of the patient at the time of presentation. Symptoms of hypogonadism are uncommon prior to the onset of puberty, with absence of pubertal development and amenorrhoea (absence of menarche) considered the main features. Following puberty, features of hypogonadism include secondary amenorrhoea, perimenopause and infertility. Hypogonadism is commonly caused by the onset of menopause in women, which occurs on average around the age of 50.

Hypogonadism can be congenital or acquired. The most common genetic disorders causing primary hypogonadism are Turner syndrome (in women) – a rare condition affecting the X chromosomes; and Klinefelter syndrome (in men), where an extra X chromosome is present. Kallmann syndrome, a condition characterised by delayed or absent puberty and an impaired sense of smell, is caused by a genetic disorder leading to secondary hypogonadism.

Diagnostics

To diagnose hypogonadism, serum levels of oestrogen (women) and testosterone (men) are measured. In addition, luteinising hormone (LH) and follicle-stimulating hormone (FSH) are also determined, as both LH and FSH are pituitary hormones secreted by the gonads. Prolactin, a hormone released by the pituitary gland, is also commonly measured.

In men, persistently low morning testosterone in conjunction with elevated LH is indicative of primary hypogonadism, whereas low testosterone in the presence of low or normal LH levels suggests secondary hypogonadism.