Sunday, November 06, 2005

Folliculogenesis and ovulation

I learned from my reproductive endocrinology text that eggs are constantly moving from stasis into a maturation process. The lucky ones synch up correctly with the hormonal cycle and have a chance at ovulation. The other eggs are just reabsorbed.

Oocytes (unmatured eggs) are held in stasis by hormones, and the micro-environment of the follicle needs to move from testoterone-dominant to an estrogen-dominent in order to be considered for ovulation. Often women with PCOS or thyroid problems have issues with their hormones that might impair this process such as high levels of androgens.

It might be possible that prolonged development of the follicle might cause the egg not to mature as well as a tighter hormonal cycle but I haven't read anything to that effect -- mind you I haven't researched that specifically though.

So anyway, your ovaries are constantly maturing eggs regardless of your hormonal cycle. This might also explain why women can sometimes get pg at odd times in their cycle -- such as WWII wives who supposedly got pregnant when their husbands were on leave.

Here are some links to reference maturation of the oocyte:


Section 13: Female Reproductive System

During a woman's reproductive years, several follicles in the growing pool are recruited each cycle, and only one is usually selected for ovulation (see Fig. 234-4). It develops into a graafian (preovulatory) follicle, which can respond to the midcycle LH surge. The mechanism of selection is unknown.

The graafian follicle contains an antrum (fluid-filled cavity), created by proliferating granulosa cells, which secrete fluid and mucopolysaccharides. The increase in the follicle's size is due primarily to accumulation of follicular fluid under the control of FSH, which also induces the development of specific LH receptors on granulosa cells. LH receptors are responsible for the stimulation of progesterone secretion before ovulation and for continued production of progesterone in the luteal phase. The granulosa cells in the follicle also develop specific membrane receptors for prolactin, which decrease in number as the follicle matures; their physiologic role is unclear.

Merck Manual Chapter 234. Reproductive Endocrinology

Diagram of folliculogenesis

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