The drugs appear to impair the body's ability to break down fat correctly, causing a loss of peripheral fat under the skin and an increase in visceral fat, typically around the intestines and liver. These problems also affect men taking protease inhibitors and non-protease HIV drugs. It's too soon to tell what this trend means for women. Estrogen, progesterone, and other hormones are the cogs and wheels of the body's biological clock. For women with HIV, hormones may also play an important role in drug levels and distribution.
Scientists speculate that women's hormones delay breakdown of the drug.
There's also compelling evidence that women's hormones play a role in their risk of becoming infected or getting sick. In human studies, the hormone causes a thinning of the vaginal membrane and increased expression of a protein receptor called CCR-5 that acts as a doorway to allow HIV to enter immune cells. Women's progesterone levels are also affected by pregnancy and birth control pills, which may interact with HIV drugs that are metabolized by the same liver pathways. But here again, we lack specific information about whether women on therapy should avoid oral contraceptives. At Johns Hopkins, scientists are investigating the possibility that estrogen may help women maintain a lower viral load.