Menopause

In females, the reproductive period, or fertility period refers to the years of monthly menstrual cycles between the first menstrual period, which happens at puberty and then the permanent stopping of menstrual cycles - which is called menopause. Menopause usually sets in around age 50, and it’s preceded by a couple of years of hormonal and physical changes and this is called perimenopause. To be more specific, a woman’s entered menopause when an entire year has passed since her last menstrual period.

During the reproductive period, the ovaries have basically got a ton of ovarian follicles scattered inside them. And each ovarian follicle is made up of a ring of granulosa and theca cells surrounding a primary oocyte the core. And during each menstrual cycle, one of these follicles ruptures at ovulation, and it releases the oocyte out into the fallopian tube - where it can be fertilized by a sperm, or it can just carry on down its path and you don’t get pregnant. So the weird thing is, even though females are born with millions of follicles, only about 400 of them are actually mature enough to release their oocyte throughout the lifetime.

Anyway, all of this process is ultimately controlled by the hypothalamus, which is all the way away from the gonads up in the brain. And the hypothalamus secretes gonadotropin releasing hormone, or GnRH, which travels to the nearby pituitary gland and makes it secrete two hormones of its own - follicle-stimulating hormone, or FSH, and luteinizing hormone, or LH. FSH and LH then make the ovarian follicles secrete sex hormones. So, the theca cells make androstenedione, a sex hormone precursor that the granulosa cells convert into estradiol - a member of the estrogen family - and progesterone.