The ovary of a normally cycling female (with regular menstrual periods) maintains and responds to a very delicate balance of hormones produced in several hormonal control centers in the body. These control centers are very easily disrupted. If disruption occurs, an imbalance of these important control hormones may result. This can often times cause improper amounts of the important ovarian control hormones, FSH and LH to be produced. This may cause the ovary to "stall" in the early first part of a menstrual cycle. As a result of this stall, abnormally elevated amounts of estrogen and androgen (male hormone) may result. If the disorder persists, stalled eggs become trapped in the ovary, the ovary enlarges and more androgen and estrogen are produced. Excess androgen (male hormone) and estrogen along with the failure to ovulate due to the stalled eggs can produce infertility.

The lining of the uterus, the endometrium, stimulated by the continuously high estrogen, becomes thickened. This causes the heavy and irregular bleeding often seen in PCOS. The high androgens, in turn, may cause male pattern hair growth to occur. This male pattern hair growth may include hair growth on the chin, the upper lip, around the nipples, on the lower abdomen and on the arms and legs.


A very dramatic finding in the investigation of possible causes of PCOS was the note that most women with PCOS demonstrate a resistance or insensitivity to the action of insulin. Insulin is a natural hormone produced in the body by the pancreas. Insulin serves many vital functions in the body, but perhaps it's most important function is the transport of sugars from the blood to the inside of human cells. This action provides cells with the sugar energy source they need to stay alive and function properly. Women with PCOS who become pregnant have an increased tendency to develop diabetes during their pregnancy. It has been known for years that pregnancy makes it harder for the insulin of all women, PCOS or not, to transport sugar from the blood into the cells. As a result, sugar levels in pregnant women rise in the blood because the sugar has difficulty being moved into the cells. The normal reaction to this is for the pancreas to produce extra levels of insulin that in turn push the sugar harder to enter the cells, maintaining a normal sugar level in the blood. But in women with PCOS, it was found that in spite of making extra insulin, in many cases, they were unable to keep their blood sugar levels normal. This is because in non-PCOS women, the extra insulin they make when pregnant works normally and assures that the extra sugar is moved into the cells. In women with PCOS, pregnant or not, the insulin made by their bodies is fought or resisted by the body, making it much harder for the insulin to do it's job of moving the sugar into the cells. When the combination of the anit-insulin action of pregnancy is added to the insulin resistance seen with PCOS, many women with PCOS are simply unable to move sugar adequately and the levels of sugar in their blood rise to abnormal levels, resulting in what is termed gestational (while pregnant) diabetes. In such instances, these women are prescribed supplemental insulin injections to assist their own insulin in coping with the movement of sugar into the cells. After birth, with the removal of the anit-insulin actions caused by the pregnancy, most of these women will return their blood sugars to normal wothout the need for supplemental insulin. However, because of the poor function of their insulin, they need to produce levels of insulin far greater than women wthout PCOS

For women with PCOS who are not pregnant, the resistance of their body to the actions of insulin causes them to produce extra high levels of insulin at all times, as they struggle to move sugar into the bodies cells. This chronic strain on the pancreas may be responsible in pat for the development of obesity, and the tendency toward diabetes in many women with PCOS.


Medications that have for years been used to treat diabetics that do not require insulin (adult onset or type 2 diabetes) have been found to lower insulin levels back to normal in many women with PCOS that have elevated insulin levels. In addition, from 20 to 50 percent of women with PCOS who begin taking these medications, called insulin "sensitizers" will have their menstrual cycles become regular or near regular and many experiencing infertility will becom pregnant. The insulin sensitizers have also been noted to seem to decrease the incidence of miscarriage, which is often higher in untreated women with PCOS.