Menarche : a. indicates the start of female reproductive activity, and is triggered by the pituitary gland
b. generally occurs for most women between 45 and 55 years of age.
c. results in lower hormone levels
d. none of the above

A

Explanation: Menarche is the occurrence of a first menstrual period in the female adolescent. Menstruation is the monthly shedding of the functional layer of the uterine endometrial lining that occurs when ovulation is not followed by fertilization. It occurs approximately every 28 days, with a range from every 21 to every 45 days. The average age of onset of menarche is 12.4 years. Most menstrual periods last between 3 and 7 days. Menarche signals maturation of the adolescent female body. It commonly is associated with the ability to ovulate and reproduce.

Menarche is the result of complex interactions between the hypothalamic, pituitary, and ovarian hormones. It also can be affected by thyroid, adrenal, and pancreatic hormones. Pulsatile hypothalamic production of gonadotropin-releasing hormone (GnRH) at puberty stimulates the pituitary production of follicle stimulating hormone (FSH) and luteinizing hormone (LH). FSH and LH, in turn, stimulate an increase in ovarian production of estrogens, primarily estradiol, and androgens. Estradiol promotes maturation of ovarian follicles, with one follicle gaining dominance during each menstrual cycle. Increasing levels of estrogens stimulate uterine endometrial proliferation and eventually cause a surge of LH production by the pituitary. This LH surge causes ovulation or rupture of the dominant ovarian follicle.

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