amenorrhoea

n.

the absence or stopping of the menstrual periods. It is normal for the periods to be absent before puberty, during pregnancy and milk secretion, and after the end of the reproductive period (see menopause). In primary amenorrhoea the menstrual periods fail to appear at puberty, due to absence of the uterus or ovaries, a genetic disorder (e.g. Turner's syndrome), or hormonal imbalance. It is diagnosed when menarche has not occurred by the age of 16½ years but there is normal development of secondary sexual characteristics or by the age of 14 years if secondary sexual characteristics are absent. In secondary amenorrhoea the menstrual periods stop after establishment at puberty for a minimum of six months. Causes include disorders of the hypothalamus (a part of the brain), deficiency of ovarian, pituitary, or thyroid hormones, mental disturbance, depression, anorexia nervosa, or a major change of surroundings or circumstances.