The abnormal hormone action seen in PCOS can best be understood by first discussing the normal hormone patterns required for ovulation.
Two Hormones Secreted
There are two hormones secreted by the pituitary gland in the brain. They are FSH (follicle stimulating hormone) and LH (luteinizing hormone). FSH acts on the ovarian follicle to stimulate maturation of the egg or ovum. At the time of ovulation, there is a surge of LH which in part is responsible for rupture of the follicle and release of the egg. The ruptured follicle then becomes the corpus luteum. Under stimulation of LH, the cells that make up the corpus luteum undergo a luteinizing process.
Abnormal Levels of Hormones
In the patient with PCOS, a variety of any of these hormones may be produced at an abnormal level, perpetuating incomplete follicular development without consistent ovulation. Since the hormonal system operates as a feed-back loop, when any hormone is at an abnormal level, all related hormones are affected.
Specifically, LH levels can be higher than normal resulting in an increased LH/FSH ratio, with stimulation of the ovarian follicle but not resulting in maturation and release of the egg.
The elevated LH, levels stimulate luteinization of the cells surrounding the follicle, which results in a shift in ovarian hormone production towards increasing testosterone levels and, indirectly, a change in estrogen levels. This feeds back on the LH/FSH production and can affect the normal ratio. Therefore, not only are there the peripheral effects of increased testosterone production (increasing hair growth, but also menstrual dysfunction.