Transcript: Recent published research notes that 40 percent of women experience reduced sex drive while taking the birth control Pill.  Why? A key component in female sexual desire is testosterone, a hormone many think of as being “male.”  But women have it too, and every month when ovulation occurs, their ovaries actually make excess testosterone.
Biologically, that’s because women are fertile when they’re ovulating, and the body secretes testosterone to encourage reproductive behavior!  But, women taking hormonal contraceptives don’t have active ovaries, so the testosterone normally made there—50 percent of the body’s production—isn’t secreted.
A woman’s adrenal glands make the other half of her testosterone, and they, too, are affected by the Pill.  Why? The Pill doesn’t just reduce testosterone production—it also encourages the liver to make a protein called SHGB, which hiders its effect.  That’s because, when someone pops the Pill, the liver erroneously assumes the body has produced too much estrogen and fights back with the SHGB.