May 19, 2005 -- A new study of women with female sexual dysfunction shows that some hormonal effects seen with oral contraceptives don't disappear right away.
The findings were reported in Washington at the American Association of Clinical Endocrinologists' 14th Annual Meeting and Clinical Congress.
"These results suggest that the hormonal changes induced by oral contraceptives are not immediately reversible after discontinuation of oral contraceptive use," write the researchers, who included Claudia Panzer, MD, at Boston University's medical school.
Birth control pills have been associated with sexual dysfunction and a decrease in sex hormones, which may drive libido. They are known to decrease levels of the sex hormone testosterone in women by increasing its binding to proteins in the blood, say researchers.
The study included 101 women, all of whom had female sexual dysfunction. A total of 62 women were taking oral contraceptives; they were 37 years old, on average.
Thirty-nine other women had stopped taking oral contraceptives at some point during their treatment of female sexual dysfunction; they were 33 years old, on average. For comparison, researchers also studied 23 women who had never taken oral contraceptives (average age: 36).
Panzer and colleagues checked the women's levels of sex hormone-binding globulin (SHBG), which is made by the liver. This protein binds to the sex hormones and helps evaluate the level of free hormone; higher levels of the protein are thought to decrease testosterone.
They found that SHBG levels were four times higher in the women taking oral contraceptives than in those who had never used birth control pills.
Women who had stopped using oral contraceptives had SHBG levels somewhere in between those two groups. "Despite discontinuation of oral contraceptive use, SHBG levels remained continuously elevated for up to one year," researchers write.
Possible Impact on Androgen
Higher SHBG levels might mean lower levels of androgen "for a prolonged period" after stopping oral contraception, write Panzer and colleagues.
The study doesn't question the effectiveness of birth control pills, and it doesn't specify which oral contraceptives the women were taking. It also does not say how long the women had taken oral contraceptives.
WebMD contacted the makers of two oral contraceptives; responses were not made available before deadline.
Doctor's View on Oral Contraceptives
SHBG levels are related more to libido than pregnancy, says Christiane Northrup, MD, an obstetrician-gynecologist and author of books including Women's Bodies, Women's Wisdom and Mother-Daughter Wisdom: Creating a Legacy of Physical and Emotional Health.
The pill lowers testosterone levels in some (but not all) women, says Northrup.
She says some women who go on the pill to "regulate their periods" in their mid to late teens may have underlying health problems that are masked while on the pill.
"It's not the pill that's causing the problem; they had the problem to begin with," Northrup tells WebMD.
"If [a woman] was on the pill and was fine with the pill and never had problems with sexual function, she is probably not going to have any problem off it, either," says Northrup.
"The ones I worry about went on the pill, found their libido went away, and thought something was wrong with them -- 'What happened to my zoom zoom here?'" says Northrup. "It doesn't mean it won't come back. It will.
"If you notice a change in your desire, it may or may not be the pill," says Northrup, saying female sexual dysfunction is complicated and isn't always purely physical.