amenorrhea, cessation of menstruation. Primary amenorrhea is a delay in or a failure to start menstruation; secondary amenorrhea is an unexpected stop to the menstrual cycle. It is caused by dysfunctioning of the pituitary gland, ovaries, uterus, and hypothalamus, by surgical removal of the ovaries or uterus, by medication, or by emotional trauma. The result is an inadequate amount of body fat, calories, and protein to sustain menstruation. Female athletes have a higher than average rate of menstrual dysfunction, particularly amenorrhea, but the long-term effects of the exercise-related disorders are not known. It is also common among anorexics. The lack of estrogen, however, may contribute to the development of osteoporosis. Hormonal deficiencies over prolonged periods of time, particularly in combination with poor diets, may cause luteal phase deficiency and hypoestrogenic amenorrhea, which may last a long time. Methods of treatment include oral contraceptives or estrogen-progestin therapy.

Lack of menstruation. Signs of primary amenorrhea (failure to start menstruating by age 16) include infantile reproductive organs, lack of breasts and pubic hair, dwarfism, and deficient muscle development. In secondary amenorrhea (abnormal cessation of cycles once started), the genitals atrophy and pubic hair diminishes. Not itself a disease, amenorrhea reflects a failure in the balance among the hypothalamus, pituitary gland, ovaries, and uterus; tumours, injuries, or diseases of these can lead to amenorrhea. Other causes include systemic diseases, emotional shock, stress, hormone over- or underproduction, anorexia nervosa, absence of ovaries or uterus, pregnancy, lactation, and menopause. Infrequent menstruation or amenorrhea not resulting from organic disease is not harmful.

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