Follicle Stimulating Hormone (FSH) - In women FSH is often used as a gauge of ovarian reserve. In general, under 6 is excellent, 6-9 is good, 9-10 fair, 10-13 diminished reserve, 13+ very hard to stimulate. In PCOS testing, the LH:FSH ratio may be used in the diagnosis. The ratio is usually close to 1:1, but if the LH is higher, it is one possible indication of PCOS. Basic hormone testing for males often only includes testosterone and FSH. However, in cases such as Klinefelters Syndrome doctors will usually look at both FSH and LH levels. In males FSH stimulates the Sertoli cells in the testes to produce androgen-binding proteins, testosterone, and a protein called inhibin. Inhibin, in turn, travels in the blood back to the pituitary gland whre it creates a "negative feedback loop" that decreases the output of FSH. Since FSH stimulates testosterone production, and testosterone can be converted to DHT and estradiol, an increase of any or all three can also create a "feedback loop" that decreases FSH secretion.
Information from the Nurses' Health Study indicated that the combination of estrogen and androgen used to treat hypoandrogenism could increase breast cancer risk. However, other studies indicated androgens may decrease breast cancer risk. Follow-up studies on the Women's Health Initiative found women who received estrogen and no progestogen showed a significant decrease in cardiovascular disease (CVD) and breast cancer. This has caused a reconsideration of androgens added to estrogens. Still, the FDA requires demonstration of CVD and breast cancer safety for any product containing androgens or estrogen plus an androgen; that has not been done.