Do OCs impact libido? More research needed
A patient tells you she heard a news story that said that oral contraceptives (OCs) have lasting effect on hormone levels, dulling a woman’s sexual desire. What is your response?
New findings from a small retrospective study indicate that use of birth control pills is associated with elevated sex hormone-binding globulin (SHBG) levels and reduced bioavailable testosterone. This effect may persist even after discontinuation of pill use, researchers note.1
The study examined SHBG levels in 124 premenopausal women who had reported sexual dysfunction for at least six months; 62 of the women were current Pill users who had been taking OCs for longer than six months (called continued users), 39 who had used OCs for longer than six months and then discontinued use, and 23 women who had never used the method. All patients were offered use of transdermal testosterone therapy to improve sexual function. Sex hormone-binding globulin levels were measured at four points during the study: at baseline, while using oral contraceptives, at a mean of 80 days after discontinuing pills, and then again at more than 120 days after discontinuation.1 According to the research, SHBG levels in the women who continued to use pills were four times higher than those in the never-user group. Despite a decrease of more than 50% in SHBG values after discontinuation of Pill use, SHBG levels in women discontinuing pills remained elevated for more than 120 days (mean of 234 days) in comparison with those who had never used the method.1
Researchers note six limitations of the study: its retrospective approach; the small size of the study population; the use of a variety of combined OCs for different lengths of time by study participants; the use of various laboratories to analyze blood samples, rather than one central lab; the difference in blood test result reporting by the various laboratories; the use of testosterone transdermal patches by many of the study participants; and the fact that all women in the study had sexual dysfunction. Further research is needed to determine if long-term sexual, metabolic, and mental health consequences might result as a consequence of chronic SHBG elevation, the authors conclude.
What would be the next step in this line of research? Claudia Panzer, MD, lead author of the new study and a former endocrinologist at Boston University Medical Center, believes an ideal investigation would include a group of women who never used OC who at baseline have androgen and SHBG levels drawn and complete sexual function questionnaires. Women then would initiate pill use and would undergo scheduled blood tests and questionnaires, with pill use stopped, blood tests repeated, and further questionnaires completed, says Panzer, who now is affiliated with Rose Medical Center in Denver.
How does the Pill work?
To understand the results of the new study, it helps to review how the Pill functions. To prevent ovulation, the Pill suppresses follicle-stimulating hormone (FSH) and luteinizing hormone (LH). The progestins in oral contraceptives suppress LH, which results in decreased androgen synthesis and ultimately an overall decrease in ovarian androgen (testosterone) production.2
The Pill also increases SHBG levels, which translates into increased binding of testosterone. The estrogen component of OCs increases plasma levels of SHBG, while the progestin component has the opposite effect. The overall balance promotes liver production of SHBG, resulting in a net increase in SHBG levels. In turn, the increase in SHBG lowers the bioavailability of circulating androgens.2
Do OCs affect libido?
More research definitely is needed when it comes to the impact of the Pill on libido, says Cynthia Graham, PhD, clinical psychologist with the Kinsey Institute for Research in Sex, Gender, and Reproduction at Indiana University in Bloomington and the University of Oxford, England. She has been involved in research regarding the effects of oral contraceptives on sexuality.3-4
Graham and fellow researchers are analyzing data from a prospective study of 61 women who were randomized to one of two low-dose oral contraceptives and assessed for a period of time for changes in mood, menstrual cycle symptoms, and sexual functioning. Researchers are particularly interested in whether such side effects are related to the degree of reduction in free testosterone, she says. The research group plans to publish its findings upon analysis completion, Graham adds.
She notes that it is just a minority of women who report negative effects of the Pill on their sexual feelings. Many women actually say they feel more interested sexually because they are using a very effective method of birth control, says Graham.
- Panzer C, Wise S, Fantini G, et al. Impact of oral contraceptives on sex hormone-binding globulin and androgen levels: A retrospective study in women with sexual dysfunction. J Sex Med 2006; 3:104-113.
- Understanding OC progestins: Is "androgenicity" clinically relevant? Contraception Report 1999; 10:4-8.
- Sanders SA, Graham CA, Bass JL, et al. A prospective study of the effects of oral contraceptives on sexuality and well-being and their relationship to discontinuation. Contraception 2001; 64:51-58.
- Graham CA, Ramos R, Bancroft J, et al. The effects of steroidal contraceptives on the well-being and sexuality of women: A double-blind, placebo-controlled, two centre study of combined and progestogen-only methods. Contraception 1995; 52:363-369.