In medicine the word primary can denote primacy in one of 3 ways: (1) event-wise (e.g. primary amenorrhea is when there has been no precedent -- no prior period -- whereas secondary amenorrhea) follows prior periods, and likewise the distinction between primary infertility and secondary infertility, a distinction based on prior successful pregnancy); (2) developmentally or time-wise (e.g. a primary follicle gives rise to a secondary follicle, then to a tertiary follicle); or (3) causally (e.g. primary ovarian failure is based within the ovary itself, whereas secondary ovarian failure is secondary to failure of gonadotropins). These sort of distinctions is one reason why medical school takes a long time.

Amenorrhea when a woman has never had a spontaneous menstrual period, that is, a period not brought on by hormone treatment.

The first stage of growth or further development of the follicle, in which the egg is enclosed by a single layer of round-shaped follicle cells, which are multiplying. The majority of primary follicles undergo atresia; a minority develop into secondary follicles.

Trouble getting pregnant (infertility) in someone who has never had a successful pregnancy. Although the exact definition can vary among gynecologists, the differentiation between primary infertility and secondary infertility is most useful if a prior ectopic pregnancy or a prior miscarriage is consistent with the state of primary infertility, whereas a prior induced abortion (which, the odds are, would otherwise have developed normally) means the state is secondary infertility.

The form of the ovum, or egg, produced in the ovaries of fetuses by oogonia that have begun the first part of the cell division known as meiosis (by which the chromosomes will eventually halve in number). Persists into childhood and adult life by containment in follicles. Gives rise to a secondary oocyte and the first polar body just before ovulation.

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.

The form of the sperm cell (or male gamete) at the first stage of spermatogenesis, by which spermatogonia enter meiosis to start to reduce the number of chromosomes for the more mature sperm cells (the spermatozoa) that will eventuate.

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.

Painful menstruation. Can be primary, present in teenagers, generally in spasms around the start of the period; or it can be secondary, developing as a woman gets older, and then typically lasting more than a day or so into the period, with prolonged aching as well as spasms. Primary dysmenorrhea might have no medical importance beyond the suffering the pain causes, and typically gets better as a woman reaches her 20s; severe or persistent cases, however, warrant investigation. Secondary dysmenorrhea can signify, for example, endometriosis, fibroids, adenomyosis or peritubal adhesions.

The process by which a primary follicle or a tertiary follicle stops growing, leading to disappearance (apoptosis) of its follicle cells and the oocyte, or egg, they contain. Such a follicle is called an atretic follicle.

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.

Maturation in the laboratory of the egg (as a primary oocyte) obtained from an immature tertiary follicle until it becomes a secondary oocyte competent to be fertilised by sperm using in vitro fertilisation. The smaller the follicle, the lower the proportion of eggs that mature successfully. ICSI can be used to increase the proportion of eggs that will fertilise, but the embryos on average do no better, and so no advantage is conferred by ICSI in this situation.

Congenital absence of gonadotropin releasing hormone in the hypothalamus (causing, in women, primary amenorrhea and anovulation and, in men, failure of puberty) in combination with a congenitally absent sense of smell.

A process similar to mitosis in which two successive divisions of a diploid cell's nucleus result in four 'daughter' cells, each with a haploid number of chromosomes. Unlike mitosis, each chromosome therefore duplicates just once (before the beginning of meiosis). Meiosis in humans (and other higher animals) takes place only among the germ cells (oogonia and spermatogonia, which will have been multiplying by mitosis. By differentiating into, respectively, primary oocytes or primary spermatocytes, each with 92 chromatids, meiosis commences. With completion of the first meiotic division the products (including secondary oocytes and spermatocytes) each contain 46 chromosomes. With completion of the second meiotic division the haploid number (23) of chromosomes, suitable for fertilisation, is reached. In the testis, meiosis and the production of new sperm cells (spermatozoa) can continue throughout life, but in the ovary all egg cells that survive commence meiosis about 20 weeks before birth, spending the remaining time (up to 50 years or more) locked up in primordial follicles as primary oocytes. Whereas a primary spermatocyte gives rise to four haploid sperm cells, a primary oocyte produces just one secondary oocyte (the spare 46 chromosomes are dumped into the first polar body just before ovulation), and then one egg cell (the spare 23 chromosomes are dumped into the second polar body after fertilisation).

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.

A tiny, compact packet of excess chromosomes discarded first by the primary oocyte as it becomes a secondary oocyte just before ovulation -- the first polar body, with 46 chromosomes; and second by the secondary oocyte immediately after fertilisation (or after activation by other means) -- the second polar body, with 23 chromosomes. The polar bodies lie in the perivitelline space. The chromosome content of each polar body can be tested as part of a preimplantation diagnosis maneuver to infer whether the corresponding oocyte has an aneuploidy: an extra chromosome in the polar body means a chromosome not enough in the oocyte, and vice versa; this is called polar body analysis.

The resting, unstimulated stage of the follicle, in which the egg (as a primary oocyte) is enclosed by just a few thinly stretched follicle cells. Primordial follicles persist in the ovary from fetal life to the time of menopause, declining in number every day during this time, as some start to develop into primary follicles, most of which then are lost through the process of follicular atresia. What the stimulus or signal is for a particular primordial follicle to start growing remains completely unknown (it is independent of FSH).

The word is used medically in one of three ways: (1) part of a sequence, as in primary follicle, secondary follicle, tertiary follicle; (2) when a person has a precedent for a contrary state (e.g. secondary amenorrhea, when a woman has had at least one spontaneous menstrual period, but then menstruation stops; secondary dysmenorrhea means periods that have painful after having been not so -- or not-so-much; secondary infertility means having trouble getting pregnant despite having become pregnant successfully in the past); or (3) when the source of dysfunction lies elsewhere (e.g. secondary ovarian failure means ovaries that do not function because, in this example, the pituitary gland on which the ovaries depend is not functioning).

The second stage of growth of the follicle, in which the egg (as a primary oocyte) is enclosed by a layer that's more than one cell thick of round-shaped, multiplying follicle cells. Virtually all secondary follicles will go on to become tertiary follicles.

Trouble getting pregnant (infertility) in someone who has previously had a successful or potentially successful pregnancy. Although the exact definition of secondary infertility can vary among gynecologists, for me the distinction between secondary infertility and primary infertility is most useful if the term secondary infertility is restricted to when there has been a prior induced abortion (which, the odds are, would otherwise have developed normally) or a successful pregnancy; a prior ectopic pregnancy or a prior miscarriage is, in my view, still the state of primary infertility.

The form of the oocyte, or egg, produced from the primary oocyte late in the life of the maturing follicle, just before ovulation. The egg stays at this stage until fertilisation by a sperm cell (spermatozoon).

The form of the sperm cell in the second stage of spermatogenesis (through which the sperm cells are formed in the testes), produced from primary spermatocytes in the first cell division of meiosis, and giving rise to spermatids, which have just half the normal cell's complement of chromosomes, through the second division of meiosis; enveloped by Sertoli cells in the testicular tubules.

Measurement of follicle stimulating hormone in serum. Useful at the time of menstruation for indicating a significantly decreased number of eggs in the ovaries in the few years leading up to menopause (that is, indicative of depletion of eggs or primary ovarian failure); Continuously high in women after menopause, and then excreted in high amounts in the urine (from which, in turn human menopausal gonadotropin is derived).

The replicating phase of the sperm cell in the testis, equivalent to the oogonium in the ovaries, but, unlike the oogonia, spermatogonia normally persist until old age. Located among the supporting cells (Sertoli cells) in the testicular tubules. Divides by the process of mitosis until it begins to undergo meiosis by changing into the primary spermatocyte, the first step in the process of sperm cell formation, or spermatogenesis. Plural: spermatogonia.

The state of absolute infertility or complete infertility, with no chance of getting pregnant without special help. Causes include azoospermia, anovulation (especially primary ovarian failure), and blocked fallopian tubes.

A state of intersex in which the karyotype is male (i.e. 46,XY), the gonads are testes (hence also male), but the body is completely unresponsive to testosterone and to its metabolite dihydrotestosterone, so it develops in the female way, with a normal vulva and vagina apparent at birth, and with normal development of the breasts at puberty. Because the testes still secrete anti-Mullerian hormone, there's no uterus. Invariably these children are raised as girls, normal except for their primary amenorrhea and their infertility. Specialist medical supervision is needed, because there is an increased risk of cancer in the abnormal gonads. Synonymous with androgen insensitivity syndrome (complete form).

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.

A trisomy for chromosome number 21, or an extra chromosome-21. This is the most common of the trisomies and gives rise to Down syndrome. Research has shown that the commonest source of the extra chromosome is a mistake in the first division of meiosis in the egg cell (during the many years it rests as a primary oocyte).

The combination of primary ovarian failure with constitutional (that is, genetically determined) shortness; often with other clinical abnormalities, including 'webbing' of the neck; an increased 'carrying angle' at the elbow; short fourth metatarsal (feet) and metacarpal (hand) bones (the bone within the hand that leads to the ring finger), and sometimes abnormalities of the heart and the thyroid gland. Associated with a karyotype that is 45,X (a monosomy, with one sex chromosome missing) or with partial loss ('deletion') of one of a pair of X-chromosomes. The single X-chromosome present can come from the mother or the father -- and, interestingly, it behaves differently: if it comes from the mother the girl is likely to be rather socially disruptive (the way little boys typically are), whereas if the X-chromosome comes from the father her behavior tends to be closer to normal for that of a girl!

The tough but glassy-looking membrane that starts to surround the egg (the primary oocyte) while it's still in the follicle, protects it against sperm which have not undergone the acrosome reaction at its surface, and keeps the cells of the early embryo together until the embryo, as a blastocyst, hatches through it in preparation for implantation.