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1. The adult ovary has no stem cells. Oocytes represent cells in the prolonged prophase of the first meiosis which starts during foetal life and is completed during maturation of the oocyte after puberty. 2. Oestrogens are formed by the granulosa cells under the control of FSH which also stimulates the development of the Graafian follicle, LH is responsible for ovulation, development and maintenance of the corpus luteum and also controls the secretion of progesterone. The secretion of FSH and LH is regulated by the releasing hormones formed in the hypothalamus as well as by negative and positive feedback of oestrogen and possibly also progesterone. 3. After irradiation, the oocytes die in interphase. A dose of 4–18 Gy induces sterility depending on age; young women require higher doses than old women. After such a dose recovery is rare but may exceptionally occur from persistent small radioresistent follicles. After a dose of 150 cGy menstrual function is normal but may be followed by reduced fertility, increased risk of miscarriage and genetic mutations. 4. Ovarian damage is not influenced by fractionation apparently due to a poor repair capacity. 5. The germ cell and the endocrine ovarian functions are closely linked. Sterility is hence associated with manifestations of artificial menopause. 6. Young girls irradiated before puberty may show elevated gonadotrophin serum levels indicating ovarian damage. 7. Alkylating agents and anti-metabolites can produce temporary or permanent amenorrhoea depending on dose. The effect is thought to be due to damage of theca cells, but large doses may damage the ova.

A close and complex functional relationship exists between the ovary, the hypothalamus and the pituitary gland. In the active reproductive period, this means that most of the different cell types in the human ovary undergo dynamic alterations. These are expressed as changes in growth, differentiation, morphology, biochemical function and endocrine activity of the ovarian compartments, such as follicles, corpora lutea, interstitial gland cells and stroma. There is also a functional interrelationship between different cell types, for example, in response to FSH the granulosa cells of the large antral follicle may produce estrogen by aromatizing androgen synthesized by the theca cells (Fowler et al. 1978; Moon et al. 1978).

Associating the two words ‘ovary’ and ‘pregnancy’ suggests, at first sight, the corpus luteum of pregnancy, with its structure and morphological or functional history as a temporary endocrine gland, i.e. normal phenomena whose anatomy and physiology we are understanding better all the time.

The basic feature of the menopause is that the primordial follicle and its derivatives, the granulosa cells and the surrounding theca cells degenerate or fail to react to endogenous gonadotrophins. The granulosa cells in the pre-menopausal ovary are capable of producing estrogens from acetate (Figure 5.1) the most rudimentary steroid precursor, but tend to accumulate progesterone and 17α hydroxyprogesterone. The theca cells tend to produce the androgens, dehydroepiandrosterone, and particularly testosterone and androstenedione from progesterone, and continue the biosynthetic pathway to estradiol and estrone. Both granulosa and theca cells working synergistically produce steroids maximally. The stromal cells produce the androgens androstenedione, testosterone and dehydroepiandrosterone in the normal pre-menopausal ovary and this process continues in the post-menopausal ovary.

The ovarian follicle has to be considered as a composite structure — namely oocyte, cumulus, granulosa, theca and antral fluid — whose components may exert regulatory influences upon each other. The maturation of oocyte is well correlated with follicular development, which consists of the development of granulosa on the theca cell layer and steroidogenesis1, 2.

During the early embryonic life the gonadal primordia of vertebrates usually exhibit intersexuality. At a certain stage of development the sex of the individual becomes obvious as the gonad differentiates into a testis or an ovary. In contrast to many other vertebrates, the sex of the mammalian gonad is very stable. When the gonad becomes a testis or an ovary, a fixed sex-related pattern of development is imposed on the germ cells as well as on the somatic elements. Until now it has not been possible to change this pattern to such an extent that a functional sex-reversed individual could be obtained (Burns 1961).

In adult female mammals follicular growth is initiated continuously irrespective of physiological status, including pregnancy, lactation or other interruptions of cyclicity1. Although the stimulus for growth is not yet known, early development of the follicle comprises enlargement of the oocyte, proliferation of surrounding granulosa cells and the organization of a definitive theca cell layer external to the basement membrane. Continuous growth of follicles from the preantral stage through antrum formation and the time of ovulation is dependent largely on the pituitary hormones, follicle-stimulating hormone (FSH) and luteinizing hormone (LH). The entire process of growth and cell differentiation of any given follicle appears to comprise progressive changes in the response of follicular (theca and granulosa) cells to the two pituitary gonadotropins2.