Hypogonadism is when the sex glands produce little or no hormones. In men, these glands (gonads) are the testes; in women, they are the ovaries.

The cause of hypogonadism may be "primary" or "central." In primary hypogonadism, the ovaries or testes themselves do not function properly. Some causes of primary hypogonadism include:

• Surgery
• Radiation
• Genetic and developmental disorders
• Liver and kidney disease
• Infection
• Certain autoimmune disorders

The most common genetic disorders that cause primary hypogonadism are Turner syndrome (in women) and Klinefelter syndrome (in men).

In central hypogonadism, the centers in the brain that control the gonads (hypothalamus and pituitary) do not function properly. Some causes of central hypogonadism include

• Tumors
• Surgery
• Radiation
• Infections
• Trauma
• Bleeding
• Genetic problems
• Nutritional deficiencies
• Iron excess (hemochromatosis)

A genetic cause of central hypogonadism that also produces an inability to smell is Kallmann syndrome (males). The most common tumors affecting the pituitary area are craniopharyngioma (in children) and prolactinoma (in adults).

In girls, hypogonadism during childhood will result in lack of menstruation and breast development and short height. If hypogonadism occurs after puberty, symptoms include loss of menstruation, low libido, hot flashes, and loss of body hair.

In boys, hypogonadism in childhood results in lack of muscle and beard development and growth problems. In men the usual complaints are sexual dysfunction, decreased beard and body hair, breast enlargement, and muscle loss.

If a brain tumor is present (central hypogonadism) there may be headaches or visual loss, or symptoms of other hormonal deficiencies (such as hypothyroidism). In the case of the most common pituitary tumor, prolactinoma, there may be a milky breast discharge. People with anorexia nervosa (excessive dieting to the point of starvation) also may have central hypogonadism.

Tests may be done that check estrogen level (women) and testosterone level (men) as well as FSH level and LH level, the pituitary hormones that stimulate the gonads. Other tests may include a thyroid level; sperm count; prolactin level (milk hormone); blood tests for anemia, chemistries, and iron; and genetic analysis.

Sometimes imaging is necessary, such as a sonogram of the ovaries. If pituitary disease is suspected, an MRI or CT scan of the brain may be done.