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Physiology (Menstrual Cycle (Hormones are secreted in a negative and…
Physiology
Menstrual Cycle
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Hormone secretion begins in the hypothalamus where gonadotropin-releasing hormone (GnRH) is secreted in an increased, pulsatile fashion once puberty starts
GnRH is then transported to the anterior pituitary where it activates its 7-transmembrane G-protein receptor
This provides a signal to the anterior pituitary to secrete stimulating follicle hormone (FSH) and luteinizing hormone (LH).
FSH and LH provide input to the ovaries. Within the ovarian follicle, there are 2 cell types responsible for hormone production, theca cells, and granulosa cells.
LH stimulates theca cells to produce progesterone and androstenedione by activating the enzyme, cholesterol desmolase
Once androstenedione is secreted, the hormone diffuses to the nearby granulosa cells. Here, FSH stimulates the granulosa cells to convert androstenedione to testosterone then 17-beta-estradiol by activating the enzyme, aromatase
As levels of 17-beta-estradiol or progesterone increase based on the phases of the menstrual cycle, there is negative feedback back to the anterior pituitary to lower the levels of FSH and LH being produced and subsequently, the levels of 17-beta-estradiol and progesterone produced.
An exception to this is during ovulation, in this case, once a critical amount of 17-beta-estradiol is produced it provides positive feedback to the anterior pituitary to produce increased amounts of FSH and LH.
granulosa cells produce inhibin and activin, which inhibit and stimulate FSH release from the anterior pituitary, respectivel
Amenorrheoa
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Physiological states of amenorrhoea are seen, most commonly, during pregnancy and lactation (breastfeeding), the latter also forming the basis of a form of contraception known as the lactational amenorrhoea method
Outside the reproductive years, there is absence of menses during childhood and after menopause.
Primary amenorrhoea is defined as an absence of secondary sexual characteristics by age 14 with no menarche or normal secondary sexual characteristics but no menarche by 16 years of age.
It may be caused by developmental problems, such as the congenital absence of the uterus, failure of the ovary to receive or maintain egg cells, or delay in pubertal development.
Secondary amenorrhoea (menstrual cycles ceasing) is often caused by hormonal disturbances from the hypothalamus and the pituitary gland, from premature menopause or intrauterine scar formation
It is defined as the absence of menses for three months in a woman with previously normal menstruation, or nine months for women with a history of oligomenorrhoea.[4]
Menopause
permanent cessation of menstruation that results from the loss of ovarian function and therefore represents the end of a woman’s reproductive life.
At the time of menopause the ovaries contain very few follicles; they have decreased in size, and they consist mostly of atretic (shrunken) follicles, some interstitial cells, and fibrous tissue
. Estrogen production decreases by 80 percent or more, and this along with the loss of follicles results in marked increases in the secretion of luteinizing hormone (LH) and follicle-stimulating hormone (FSH).
Menstrual periods may cease abruptly or may be irregular for a year or so before ceasing. In a similar fashion, menopausal symptoms may occur abruptly or gradually.
While menopausal symptoms may begin when the woman is still menstruating, they are more likely to begin after menstruation ceases.
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