Regulation of the ovary (2)

Regulation of the ovary (2)

Small amounts of LH induce proliferation and androgen production in the dominant follicle. The androgens are converted into estrogens in the granulosa cells. LH also stimulates progesterone production in the granulosa cells. These two events result in a very high estradiol production. Both estradiol and progesterone (and other factors) take care of the oocyte maturation.

The hormone levels during the ovulatory cycle are shown in the graphic below:

In the beginning of the menstrual cycle (follicular phase), FSH is secreted from the pituitary (1) and stimulates the mitosis of the estradiol producing granulosa cells of the follicle (2). FSH

levels will drop due to the negative feedback by estradiol. When estradiol levels pass a certain threshold, they exert a positive feedback on LH secretion. LH levels peak (3) and the ovulation process occurs. One of the factors produced by granulosa cells is progesterone (4), which has a negative feedback on LH secretion (indirectly via GnRH). The remaining follicle becomes the corpus luteum: luteal phase of the cycle. When fertilization of the oocyte is absent or fails, the corpus luteum degenerates and progesterone levels drop towards the end of the cycle (5).

See also the section on female reproduction in the gynaecology chapter.

1

The hormone that induces ovulation in women and promotes the secretion of progesterone by the ovaries is

2

FSH in males supports