The menopause literally means the last menstrual period. It indicates primary ovarian failure. On average, it occurs at 51 years in the U.K., although it is slightly earlier among smokers. Physiologically, it is characterised by increased production of FSH and LH as negative feedback from serum oestrogen diminishes.

Ovarian function does not cease instantaneously. Symptoms of impending failure may be apparent several months or years before the last menstrual period. This period is known as the perimenopause or climacteric, and is what most lay people refer to as the menopause. Similarly, symptoms may persist for several years afterwards.

A woman is regarded as postmenopausal from 1 year after her final menstrual period. Sometimes it may be difficult to define precisely when the menopause occurs, especially if the woman begins to take hormone replacement therapy during the menopause.