A study getting a fair amount of airtime this week may cause women on the birth control pill some concern. Researchers reported in the current Journal of Sexual Medicine that oral contraceptives may interfere with the action of a key hormone even after women have stopped taking the drug, possibly contributing to an ongoing loss of sexual desire.

The team examined levels of a protein called sex hormone binding globulin (SHBG), which blocks the action of testosterone. Though it's thought of as a male hormone, testosterone influences desire and a host of other physiological processes in both sexes. Too much SHBG, then, can reduce the effect of testosterone and produce sexual problems like lowered desire and reduced vaginal lubrication.

The researchers found that SHBG levels in the women currently on the pill were four times higher than in those who had never taken the pill. That wasn't terribly surprising, since the link between the pill and suppressed sex hormone activity (and resulting sexual complaints) is already known. What surprised Andre Guay, a study coauthor and director of the Center for Sexual Function/Endocrinology at the Lahey Clinic in Peabody, Mass., was that the women who used to be on the pill but weren't any longer also had levels of SHBG that were higher than those who never took the pill. The levels dropped over time but after four months still didn't return to normal. Eleven women were tracked for a year, and the increase persisted. The pill may cause long-lasting changes in the level of SHBG the body normally produces.

But researchers say it's too soon to worry. The study was small and preliminary—a look back at historical data for about only 124 women with existing sexual complaints, not at the experience of the general population. And while the long-term increase in SHBG was statistically significant, it may not actually make a difference in sexual functioning, says Guay. What the research does point to, says Guay, is more research; he is interested, for example, in whether long-lasting elevated SHBG levels might later exacerbate hormonal problems experienced by some women going through menopause.