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More articles by Dr. Soucasaux: Anatomical drawings - Anovulatory cycles - Archetypal aspects of the female genitals - The breasts: some morphological aspects - Colposcopy - Comments on the corpus luteum and related aspects - Comments on some anatomical and symbolic aspects of the female pelvis - The curious relations between androgens and estrogens in women - Drospirenone Oral Contraceptives - Due to prohibition, Brazilian women don't have access to modern medicinal abortion - Endocrinology of menstruation - The Fallopian tubes - Female sexual response - The Gräfenberg Spot (G-Spot) - The Gynecologic Palpation (descendant of "The Touch") - Gynecological assistance: the three basic areas - Gynecology and Gynecologic Surgery - Gynecologist versus obstetrician: what lies behind the combination? - "Gyneco-obstetric-surgical" stubborness and the perpetuation of one of the greatest mistakes of women's medicine - Hypermenorrhea and/or Menorrhagia (Prolonged and/or Excessive Menstrual Bleedings) - Hypertrichosis, Hirsutism and Androgenic Manifestations in Women - Mayer-Rokitansky-Kuster-Hauser (MRKHauser) Syndrome - Menstrual toxin: An old name for a real thing? - Nature and the ovaries - On the Intimate, or Small-Scale, Mechanisms of Menstruation - On the Strange Nature of the Ovaries - Oral hormonal contraceptives (the "Pill") - The Ovaries: Some Functional and Archetypal Considerations - Peculiarities of the Female Genitals' Sensory Innervation - Physiology of menstruation - Polycystic ovaries syndrome - The Possibility of Becoming Pregnant, Its Implications for Women, and Abortion - Premenstrual congestion of the breasts - Premenstrual syndrome (PMS) - The Psychology of Gynecology part 1 (part 2) - Psychosomatic and symbolic aspects of menstruation - Psychosomatic gynecology - Some Details on the Function of the Hypothalamus-Pituitary-Ovaries Axis - Stanislav Grof's Perinatal Matrixes of the Unconscious and Women's Medicine - Symmetric Patterns in the Female Genitals - Thoughts on Female Sexual Psychology - Uninterrupted use of hormonal contraceptives for menstrual suppression: why I do not recommend it - The uterine cervix - Uterine contractility - The Uterus and the Female "Passive-Active" - Women's corporeal consciousness and experience - Women's Experience of the Breasts - Women's Undesired Pregnancies and Women's Right to Abortion and see his Art of Menstruation


Some Details on the Function of the Hypothalamus-Pituitary-Ovaries Axis

Dr. Nelson Soucasaux, Brazilian gynecologist

 

The amazing cyclical feature that characterizes the ovarian function and, therefore, the female endocrine physiology and the menstrual cycle, is due to an extremely intricate functional interaction between the ovaries and the hypothalamus-pituitary system, by means of feedback mechanisms. (The hypothalamus is the part of the brain that the pituitary is attached to. The pituitary or hypophysis is the gland that commands most of the other endocrine glands in the body. The pituitary function depends almost entirely on the hypothalamic control. The hypothalamus, in turn, is constantly receiving influences from other parts of the brain. It is just for that reason that we speak on the hypothalamus-pituitary system.)

Not only the hypothalamus-pituitary system controls the ovarian function, but the ovarian function also controls the hypothalamus-pituitary system. There is a continuous mutual interaction between both and it is just by means of this highly intricate interaction that the existence of the ovarian cycle is made possible. The main factors responsible for the function of the so-called hypothalamus-pituitary-ovaries axis are the hypothalamic neuro-hormones and the pituitary and ovarian hormones.

The follicle stimulating hormone (FSH) and the luteinizing hormone (LH) are the pituitary gonadotropins that control most of the ovarian function. The release of these gonadotropins by the pituitary is controlled by the hypothalamus by means of a neuro-hormone known as Gn-RH (gonadotropin releasing hormone, which is the same for the FSH and the LH). The estrogens produced by the ovaries under the FSH and LH command exert, in turn, negative and positive feedback actions upon the hypothalamic neural centres responsible for the Gn-RH production. A negative feedback action is characterized by an inhibiting effect upon some of these centres, while a positive feedback action produces a stimulation of other hypothalamic centres. In this way, the levels of estrogenic production throughout the ovarian cycle indirectly control the pituitary release of FSH and LH. On the other hand, the ovarian estrogenic production depends on the FSH and LH stimulation.

The hypothalamus-pituitary system's reaction to the feedback exerted by the estrogen levels along the menstrual cycle exhibits an ambivalent pattern which is typically female. A regimen of negative feedback predominates along almost all of the cycle; in this way, as the estrogen levels increase, the gonadotropic secretion is reduced. However, when a growing ovarian follicle reaches its mature stage, and begins the production of heightened estrogen levels within a specific "critical" threshold and duration, the opposite effect takes place and, by means of a positive feedback, the pituitary ovulatory peak of LH is released.

This is due to the action of different hypothalamic neural centres involved in this highly intricate and precise mechanism. They are: 1) a tonic center that controls the basal secretion of FSH and LH by the pituitary throughout almost all of the cycle; this centre is sensitive to the negative feedback action of the circulating estrogens; 2) a cyclical center, the one that triggers the pituitary release of the LH ovulatory peak; it is just upon it that the high estrogen levels produced by the mature ovarian follicle exerts a positive feedback action.

Now, let us say some words about the basic patterns of the FSH and LH pituitary secretion along a typical ovulatory cycle. During most of the cycle, the FSH exhibits a basically steady pattern of secretion with two slight elevations. The first elevation arises on the last days of the cycle that terminates and lasts up to the first days of the new cycle that begins; the second one is transitory and coincides with the LH ovulatory peak. These two cyclical elevations of the FSH are supposed to stimulate more effectively the growth of follicles that are in their earlier stages of development. The LH exhibits a tonical steady pattern of secretion along most of the cycle except at the pre-ovulatory period, when a great amount of this gonadotropin is suddenly released in a very short period of time constituting the LH ovulatory peak. Its purpose is just triggering ovulation and stimulating the beginning of the corpus luteum formation. This peak of LH does not occur in the anovulatory cycles.

The ovarian processes of follicular maturation, ovulation, formation of the corpus luteum and synthesis of the sexual hormones are under the control of the pituitary gonadotropins. Only the beginning of the first stage of follicular growth does not depend on the gonadotropic stimulation, being a process which the ovary, all by itself, sets in motion. From this stage on, in order to proceed their development up to the stage of mature follicle and produce good estrogen levels, the ovarian follicles depend on the FSH and LH stimulation. On the other hand, ovulation and formation of the corpus luteum depend on the LH ovulatory peak.

In the process of follicular growth and estrogen synthesis the LH stimulates mostly the theca cells, while the FSH stimulates mostly those of the granulosa. (Each growing ovarian follicle is formed by an oocyte surrounded by several layers of granulosa and theca cells. The theca cells, under the LH stimulation, produce mostly androgens, while the granulosa cells, under the FSH stimulation, turn these androgens into estrogens.) There are reports that the estrogens produced by the follicles may provide some help in these processes, since they seem to stimulate the multiplication of the granulosa cells and increase their responsivity to the FSH.

Even so, in spite of that small collaboration of the estrogens in the process of follicular growth, the FSH and the LH are, undoubtedly, the most important hormonal factors responsible for the follicular maturation and the ovarian estrogen synthesis. As an ovarian follicle proceeds its development, the quantity of FSH-receptors contained in its granulosa cells also increases and, for that reason, the follicle becomes more and more sensitive to the FSH stimulation. In this way, the follicular maturation accelerates and its estrogen production becomes higher, since it is under the action of the FSH that the granulosa cells turn the androgens produced by the theca cells into estrogens.

In the mature, pre-ovulatory follicle, the granulosa cells also become receptive to the LH. This happens because the action of the estradiol and the FSH produces a great increase of LH-receptors in these cells. In this way, immediately after ovulation ­ which is triggered by the pituitary peak of LH ­ the luteinization of the ruptured follicle takes place, giving rise to the corpus luteum. The corpus luteum produces progesterone and also estrogens, and is formed by the granulosa-lutein cells and the theca-lutein ones. Though possessing a considerable intrinsic capacity of self-regulation, the corpus luteum also depends on normal LH levels for its maintenance along its 12 to 14 days of duration throughout the second phase of the menstrual cycle.

The blockage of most of the ovarian function and the resulting suppression of ovulation induced by the use of the hormonal contraceptives is just based on the medicinal creation of a negative feedback upon the hypothalamus-pituitary system. The estrogens and progestins (synthetic progesterones) contained in the "Pill" produce an inhibition of this system, resulting on several alterations of the normal patterns of FSH and LH secretion by the pituitary. During the use of the hormonal contraceptives the basal levels of FSH and LH are slightly reduced and the ovulatory peak of LH is abolished. As a consequence, the growth of the ovarian follicles is interrupted in their earlier stages of development, no one of them reaching the stage of mature follicle and ovulation is suppressed.

The article above is an adapted excerpt from my book "Os Órgãos Sexuais Femininos: Forma, Função, Símbolo e Arquétipo" ("The Female Sexual Organs: Shape, Function, Symbol and Archetype"), published by Imago Editora, Rio de Janeiro, 1993. For more information on the book, see page http://www.nelsonginecologia.med.br/orgaos.htm at my website www.nelsonginecologia.med.br .

Copyright  Nelson Soucasaux  1993, 2005

_______________________________________

Nelson Soucasaux is a gynecologist dedicated to clinical, preventive and psychosomatic gynecology. Graduated in 1974 by Faculdade de Medicina da Universidade Federal do Rio de Janeiro, Brazil, he is the author of several articles published in medical journals and of the books "Novas Perspectivas em Ginecologia" ("New Perspectives in Gynecology") and "Os Órgãos Sexuais Femininos: Forma, Função, Símbolo e Arquétipo" ("The Female Sexual Organs: Shape, Function, Symbol and Archetype"), published by Imago Editora, Rio de Janeiro, 1990, 1993. He has been working in his private clinic since 1975.

Web site (Portuguese-English): www.nelsonginecologia.med.br

Email: nelsons@nelsonginecologia.med.br


NEWS | homepage | LIST OF ALL TOPICS | MUM address & What does MUM mean? | e-mail the museum | privacy on this site | who runs this museum?? |
Amazing women! | the art of menstruation | artists (non-menstrual) | asbestos | belts | bidets | founder bio | Bly, Nellie | MUM board | books: menstruation and menopause (and reviews) | cats | company booklets directory | contraception and religion | costumes | menstrual cups | cup usage | dispensers | douches, pain, sprays | essay directory | extraction | famous women in menstrual hygiene ads | FAQ | founder/director biography | gynecological topics by Dr. Soucasaux | humor | huts | links | masturbation | media coverage of MUM | miscellaneous | museum future | Norwegian menstruation exhibit | odor (olor)| pad directory | patent medicine | poetry directory | products, current | religion | your remedies for menstrual discomfort | menstrual products safety | science | shame | slapping, menstrual | sponges | synchrony | tampon directory | early tampons | teen ads directory | tour of the former museum (video) | underpants directory | videos, films directory | Words and expressions about menstruation | Would you stop menstruating if you could? | What did women do about menstruation in the past? | washable pads
More articles by Dr. Soucasaux: Anatomical drawings - Anovulatory cycles - Archetypal aspects of the female genitals - The breasts: some morphological aspects - Colposcopy - Comments on the corpus luteum and related aspects - Comments on some anatomical and symbolic aspects of the female pelvis - The curious relations between androgens and estrogens in women - Drospirenone Oral Contraceptives - Due to prohibition, Brazilian women don't have access to modern medicinal abortion - Endocrinology of menstruation - The Fallopian tubes - Female sexual response - The Gräfenberg Spot (G-Spot) - The Gynecologic Palpation (descendant of "The Touch") - Gynecological assistance: the three basic areas - Gynecology and Gynecologic Surgery - Gynecologist versus obstetrician: what lies behind the combination? - "Gyneco-obstetric-surgical" stubborness and the perpetuation of one of the greatest mistakes of women's medicine - Hypermenorrhea and/or Menorrhagia (Prolonged and/or Excessive Menstrual Bleedings) - Hypertrichosis, Hirsutism and Androgenic Manifestations in Women - Mayer-Rokitansky-Kuster-Hauser (MRKHauser) Syndrome - Menstrual toxin: An old name for a real thing? - Nature and the ovaries - On the Intimate, or Small-Scale, Mechanisms of Menstruation - On the Strange Nature of the Ovaries - Oral hormonal contraceptives (the "Pill") - The Ovaries: Some Functional and Archetypal Considerations - Peculiarities of the Female Genitals' Sensory Innervation - Physiology of menstruation - Polycystic ovaries syndrome - The Possibility of Becoming Pregnant, Its Implications for Women, and Abortion - Premenstrual congestion of the breasts - Premenstrual syndrome (PMS) - The Psychology of Gynecology part 1 (part 2) - Psychosomatic and symbolic aspects of menstruation - Psychosomatic gynecology - Some Details on the Function of the Hypothalamus-Pituitary-Ovaries Axis - Stanislav Grof's Perinatal Matrixes of the Unconscious and Women's Medicine - Symmetric Patterns in the Female Genitals - Thoughts on Female Sexual Psychology - Uninterrupted use of hormonal contraceptives for menstrual suppression: why I do not recommend it - The uterine cervix - Uterine contractility - The Uterus and the Female "Passive-Active" - Women's corporeal consciousness and experience - Women's Experience of the Breasts - Women's Undesired Pregnancies and Women's Right to Abortion and see his Art of Menstruation