The general name for one of the two principal female sex hormones (the other is progesterone), responsible for stimulating growth of the female reproductive system (the vagina, the cervix, the uterus and the fallopian tubes) and growth of the breasts. The main estrogen is estradiol, produced by: the developing follicle (and to a lesser extent by the corpus luteum) in the ovary; by the trophoblast of the placenta; and by the body's fat tissues (through conversion from male sex hormones, or androgens, in the blood). After the menopause the main estrogen is the weaker one, estrone, largely derived from conversion by the body's fat of the weak androgen androstenedione.

(ERT) The therapeutic use of estrogen to stop the effects of menopause after the ovaries have been removed or have stopped functioning. If the uterus is still present the hormone regimen must include at least 11 days' progestogen usage each month, or there will be a risk of endometrial hyperplasia and hence endometrial cancer.

A drug that blocks the action of estrogens and so tricks the pituitary gland into thinking the ovary's follicles are not producing enough estradiol, so that natural FSH production is temporarily increased, the ovaries thereby are stimulated, and follicles grow. The LH surge and ovulation usually follow naturally, but human chorionic gonadotropin can be given if monitoring is used to make sure the follicle is properly mature. Brand names: Clomid (Marion Merrell) and Serophene (Serono)

A progestogen that is particularly effective at blocking the effect of male sex hormones (androgens)on the skin, and therefore reducing abnormal hair growth (hirsutism) and acne. Found singly in Androcur and in combination with an estrogen in Diane-35, a formulation used for oral contraception. Dangerous if taken in pregnancy, because it stops male fetuses from developing normal genital organs. Not available in the US.

A formulation of the oral contraceptive pill that contains, as well as an estrogen, the progestogen known as cyproterone acetate, which is particularly effective at blocking the effects of male hormones on the skin. Made by Schering.

A natural or pollutant substance in the environment possibly capable of acting -- alone or in combination with other substances -- as an estrogen or as a blocker of androgens during development of the fetus. Suspected of causing endometriosis and oligospermia in later life.

Diminishment of the endometrium through lack of support by, especially, the hormone estrogen or by the loss, through chronic endometritis and/or injury at curettage under abnormally low estrogen conditions, of subsequent receptiveness to estrogen. Can cause light periods hypomenorrhea or absent periods amenorrhea.

Overgrowth of the endometrium, caused usually by prolonged action of estrogen unopposed by progesterone (i.e. prolonged anovulation), as is the case in, particularly, the polycystic ovary syndrome. Potentially dangerous, because it can turn to cancer of the endometrium. Can be suspected by an echogenic appearance of the endometrium on transvaginal ultrasound and is confirmed by pathological examination of tissue obtained at curettage.

The most powerful natural estrogen. Produced by the ovarian follicle and corpus luteum in women, and (to a small extent) by the Sertoli cells in men. Also produced by fat cells (through conversion of testosterone) in older women, especially after the menopause.

A weak estrogen. Increased in pregnancy, especially late pregnancy.

A weak estrogen, which needs to be converted (in target tissues such as the endometrium) to the strong estrogen estradiol before, as a hormone, it causes an estrogen effect. The main estrogen in blood after the menopause. Formed from estradiol when that hormone in tablet (or oral) forms is absorbed across the intestines. Abbreviated E1.

Normal structure in the ovary that contains the egg, or oocyte. All are formed as primordial follicles before birth and remain microscopic in size until growth starts (folliculogenesis), a month or two before the cycle in which the particular follicle will be a candidate to ovulate. About 3 mm in diameter at the start of a cycle, and about 2 cm in diameter when ready to ovulate. The follicle makes more and more estrogen (particularly estradiol) as it grows. In ovarian monitoring for assisted conception, the number growing and their rate of growth are monitored by transvaginal ultrasound.

Cells of the follicle that surround the egg (the oocyte). An increase in number is what causes the follicle to grow. In tertiary follicles they are responsible for converting androgens (from surrounding ovarian thecal cells) into estrogens, particularly estradiol. A tertiary follicle's cells are also called granulosa cells.

A follicle is "recruited" at two distinct stages of development. Early or continuous recruitment refers to the ongoing, continuous recruitment of primordial follicles to start their growth and become antral follicles, a process that is independent of major hormones, starts before birth and ends when there are no follicles left, this taking place around the time of menopause. Cyclical recruitment refers to the much later recruitment of medium-sized tertiary follicles into the ovarian cycle due to a temporary elevation of follicle stimulating hormone, which occurs at the end of each luteal phase, thus initiating a new follicular phase; the group of "recruits" susceptible to this late recruitment is called a cohort. Time-wise for a particular follicle, the two episodes of recruitment occur 8 months apart: in other words, it takes 8 months for a follicle to grow from its resting state before it can have a chance of making estrogen and then undergoing ovulation. Not all early-recruited follicles undergo later cyclical recruitment: some are lost through early atresia, many reach the stage at which they could be cyclically recruited at a stage when FSH is low (most stages of the ovarian cycle) and undergo atresia then. Readers will appreciate that ovulation induction, including intentional superovulation, can have no effect on the rate at which follicles are used up in ovaries or on the age at which menopause will occur (the different recruitment points involved are 8 months apart, with the early recruitment point governing the rate eggs are used up and the late recruitment point deciding how many follicles can respond to provide useable eggs.

Generic name for Dimetriose, a drug used in the treatment of endometriosis that inhibits ovulation and blocks the action of both estrogen and progesterone; risks and side effects are similar to danazol; it is usually taken just twice weekly, by mouth.

Any hormone that switches on the function of the gonads. There are two main families of gonadotropins: (a) the gonadotropin that stimulates the growth of the follicle, or follicle stimulating hormone (FSH); and (b) those that cause ovulation from the mature follicle and stimulate the corpus luteum that results to develop and to produce progesterone, namely luteinising hormone (LH) and human chorionic gonadotropin (hCG). FSH will cause growing follicles to produce the estrogen estradiol, provided that a small amount of LH (or hCG) is present. FSH and LH are produced in the pituitary gland, whereas hCG comes from the placenta in pregnancy. In men, FSH stimulates the Sertoli cells of the testicular tubules, and hence drives spermatogenesis; LH and hCG stimulate the Leydig cells to produce testosterone.

(HRT) This could literally be the replacement of any naturally deficient hormone, but in practice it means estrogen replacement therapy.

Hormone replacement therapy; see estrogen replacement therapy.

One of several tests of the ability of sperm to penetrate cervical mucus at the time of ovulation or under the influence of estrogen.

Adhesions inside the endometrial cavity caused by prior infection (endometritis), especially if there has been a curettage during the period of infection, or if curettage is performed in conditions of low estrogen. The circumstances in which this combination is most common are treatment for a missed abortion and treatment of a postpartum hemorrhage (bleeding a few weeks after the birth of a baby). A cause of absent periods amenorrhea, light periods (hypomenorrhea) or recurrent miscarriages.

An in vitro (laboratory) test of the interaction between sperm and cervical mucus, in which the mucus to be tested is drawn into two fine glass tubes (another two tubes are filled with mucus that is known to be good) to give a 4-way test between: husband's (or male partner's) sperm and wife's (or female partner's) mucus; husband's sperm and known good mucus; known good sperm with wife's mucus; known good sperm with known good mucus. Because of the laboriousness of the test it's usual to administer estrogen for at least a week in the follicular phase to ensure that the mucus is optimal.

The phase of the menstrual cycle in the endometrium during which there is menstruation, caused by withdrawal of progesterone at the end of the ovarian luteal phase as a new ovarian follicular phase starts; in anovulatory cycles or during treatment with estrogens, menstrual bleeding can occur from withdrawal, insufficiency or downward fluctuations of estrogen alone.

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.

The equivalent of the menstrual cycle in the ovary, comprising the follicular phase and the luteal phase. Thus the ordered sequence of timely development of tertiary follicles to a (usually) single dominant follicle or Graafian follicle, characterised by increasing production of the estrogen estradiol), through ovulation, when estradiol falls and progesterone starts to rise, followed by the development and then decline of the corpus luteum, with the further production of progesterone. Because estradiol and progesterone control the growth and development of the endometrium in the uterus, the ovarian cycle determines the menstrual cycle (normally lasting from 24 to 35 days in length, and with a typical duration of about 28 days) and also the cycle of the normal female hypothalamus and pituitary gland.

A mixture of estrogens in tablet form (from Ayerst Laboratories) with the reputation of being 'natural', though in reality extracted from the serum of pregnant mares (horses); the main human estrogen it contains is estrone.

(PMT) A distressing group of symptoms usually timed for the lead up to a period, then relieved as menstruation takes place, although many women experience different timing; includes downheartedness or depression (certainly an absence of well-being), aggression, fluid retention and weight gain, painful breasts ('mastalgia'), headaches and pain in the pelvis; caused by a periodic fall in the brain's endorphins, in turn usually precipitated by falling levels of progesterone in the second half of the luteal phase, although similar symptoms often accompany the use of progestogens, especially in older women; may be better during superovulation cycles because of generally higher hormone levels, but this is not always the case and PMT at the end of an unsuccessful cycle of assisted conception is particularly hard to put up with. Usually treated (up to a point) symptomatically, with perhaps fluid tablets (diuretics) and analgesics, although it's claimed that the drug Prozac has a specifically beneficial effect on mood, and encouragement of endorphin release with exercise can also be useful. Because progesterone and progestogens are the culprits, an operation to remove the ovaries (plus hysterectomy to simplify estrogen replacement therapy without needing progestogens) is usually curative, but drastic.

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 progesterone-like substance, usually more active when given by mouth than natural progesterone is. Used with an estrogen in the birth control (oral contraceptive) pill. Commonly used examples have a structure like progesterone itself (e.g. medroxyprogesterone acetate, or Provera; cyproterone acetate, or Androcur) or have a structure distantly related to the male hormone testosterone (e.g. norethisterone, or Primolut N; norgestrel)

(PRL) The hormones produced by the pituitary gland to stimulate the production of milk in the breasts. Produced in increasing amount during pregnancy, although milk secretion is postponed until levels of estrogen and progesterone fall after the baby is born. For more on prolactin in the animal kingdom, and its importance in being produced by decidual cells in pregnancy.

Failure of ovulation along with low estrogen production from the ovaries because of insufficient signalling from the pituitary gland by its hormones, the gonadotropins.

17-hydroxyprogesterone is formed from progesterone in the adrenal glands (mostly as an intermediary substance on the way to making the adrenal's main hormone, cortisol) and in the ovaries (on the way to making androgens and estrogens). A congenital lack of one or other of the enzymes needed to make cortisol in the adrenal causes androgens to be made instead, in turn causing hirsutism and oligomenorrhea in women, maybe with the polycystic ovary syndrome (in mild cases), or (in severe cases) causing intersex at birth. The adrenal glands enlarge in an attempt to maintain production of cortisol (hence congenital adrenal hyperplasia, CAH). An inappropriately high level of 17-hydroxyprogesterone in serum is diagnostic of CAH.

A layer of cells in the ovary lying immediately around the follicle; under the influence of luteinising hormone it's responsible for producing the weak male sex hormone androstenedione, which is then (1) converted by the follicle cells (the granulosa cells) into estrogen, principally estradiol, or (2) converted by other tissues outside the ovary to testosterone.