Regulation of the ovary (1)

Regulation of the ovary (1)

A follicle in the ovary consists of an oocyte surrounded by granulosa cells; the maturing oocyte makes herself an antrum. Thecal and granulosa cells are separated by a basal membrane. The thecal cells are stimulated by LH, transforming cholesterol into testosterone; granulosa cells are stimulated by FSH, making estradiol from testosterone. The regulation by the hormones of the hypothalamic-pituitary-ovary axis is shown in the second graphic below.


Gonadotropin-releasing hormone (GnRH), which is secreted from the hypothalamus stimulates the gonadotropic cells in the anterior pituitary to release FSH and LH. Estradiol produced by the granulosa layer has a positive feedback mainly on LH and a negative feedback predominantly on FSH secretion, depending on the time point in the cycle. Progesterone has a negative feedback on GnRH release from the hypothalamus and thus inhibits indirectly the LH secretion. See also the section on female reproduction in the gynaecology chapter.


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


I. Steroid hormones can easily pass cellular membranes, because they are hydrophilic structures.

II. Cholesterol is required for the biosynthesis of steroid hormones.