The most important male sex hormone is testosterone, which influences sperm production, fertility, and sex drive. Male sex hormones also promote the development of secondary sexual characteristics at puberty. Over- or underproduction of male sex hormones may be due to a variety of factors, including inherited disorders, long-term illnesses, tumours, or lifestyle factors.
Male sex hormones, or androgens, are produced mainly by the testes but also by the adrenal glands. The production of male sex hormones is controlled by hormones secreted by the pituitary gland. In turn, the pituitary gland is under the control of a part of the brain called the hypothalamus.
The changes that occur at puberty are controlled by the sex hormones. This section starts by discussing early or late onset of puberty in boys, which may be a symptom of under- or overproduction of male sex hormones. Hypogonadism, in which male sex hormones are underproduced, is covered next. In boys, this condition can suppress sexual development; in men, hypogonadism lowers sperm production and fertility. The final article discusses gynaecomastia, breast enlargement in males that temporarily affects nearly half of all boys during puberty.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.
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