Androgen deficiency

lower than normal amounts of androgens, particularly testosterone

Dihydrotestosterone (DHT)

a more potent form of testosterone (greater affinity for androgen receptors) formed by the conversion of testosterone by the enzyme 5α-reductase.


the presence of abnormally high levels of prolactin in the blood


a condition whereby the sex glands (testes, ovaries) produce little or no hormones (mainly testosterone and oestrogen, respectively)

Hypogonadotropic hypogonadism

absent or decreased function of the male testes or female ovaries. Hypogonadotropic hypogonadism is considered a form of ‘secondary hypogonadism’

Primary hypogonadism

relating to a failure of the sex glands, which may be caused by impairment of function by cytokines (e.g. impairment of Leydig’s cells in the testes by proinflammatory cytokines, such as TNF-α, IL-1, and IL-6), opportunistic infections and malignancies

Secondary hypogonadism

hypogonadism due to a problem with the pituitary or hypothalamus