When menopause occurs before the age of 40.

The natural process in which the older the female fetus, girl or woman gets the fewer are the eggs (as primordial follicles) left in the ovaries; the huge majority of eggs are lost because of atresia, only a tiny fraction by ovulation. Before the eggs are depleted there is a mild or moderate elevation in serum FSH when measured during the menstrual phase (often called a day 3 FSH. When the eggs are more or less depleted there will be primary ovarian failure and, in women who have had periods, the menopause will take place, perhaps prematurely (premature menopause). Infertility, however, usually precedes total egg depletion by up to 10 years. See also mitochondrion and oopause.

The commonest cause of severe mental retardation in males, caused by a long "triple repeat sequence" in a part of a gene for intelligence located on an X-chromosome, rendering this sex chromosome susceptible to breakage, which can be revealed either in a karyotype performed under special laboratory conditions or using a special PCR DNA test; females have two X-chromosomes and so may be carriers for this devastating condition, which will affect one-in-two of their male children; the carrier state in females can have clinical effects, namely a susceptibility to reduced numbers of ovarian follicles and hence primary ovarian failure and premature menopause, so should be looked for before assisted conception attempts are made in these clinical circumstances.

An abnormal condition of the bones, which are weakened by a loss of calcium. Deficient estrogen, such as after the menopause or after primary ovarian failure (premature menopause), eventually causes osteoporosis, with a tendency to bone fractures, especially of the wrist, the thigh and the backbone.

Failure of the ovaries to produce enough follicles, because of a problem in the ovary itself, and resulting in depletion of eggs before the age of 40 years (known as premature menopause, a cause of secondary amenorrhea), or maybe even before the age puberty is expected (causing failure of puberty to happen, including primary amenorrhea). Sometimes occurs in spite of good numbers of primordial follicles that (inexplicably, so far) won't develop. The younger the woman, the more likely that an aneuploidy will be found if a karyotype is done on blood or on a biopsy of the ovary. Estrogen replacement therapy is important to prevent general jeopardy to health, including prevention of osteoporosis.

A trisomy with a karyotype of 47,XXX -- a female with an extra X-chromosome. The old description of 'super female' is misleading, because fertility, if affected, is most likely reduced; primary ovarian failure is more common than with a normal chromosome complement and premature menopause then follows.