Shot, OC impact eyed on glucose, insulin levels
Results of a new study indicate fasting glucose and insulin levels remain within normal range for women using injectable or oral contraception, with only slight increases among women using depot medroxyprogesterone acetate (DMPA).1
The study, which was conducted over three years, is the largest to measure fasting glucose and insulin levels among women using DMPA, an oral contraceptive (desogestrel/ethinyl estradiol), and non-hormonal methods (bilateral tubal ligation, condom, or abstinence).
Some hormonal contraceptives, such as contraceptive implants and injections, have been associated with changes in carbohydrate metabolism.2,3 These changes might include decreased glucose tolerance and increased insulin resistance, which are risk factors for Type 2 diabetes mellitus and cardiovascular disease. "Previous studies were limited in scope and offered conflicting results, which led physicians to question whether hormonal contraception could lead to diabetes," says Abbey Berenson, MD, MMS, professor in the Department of Obstetrics and Gynecology and director of the Center for Interdisciplinary Research in Women's Health, both at University of Texas Medical Branch in Galveston.
Further studies are needed to determine how women with diabetes are affected by DMPA and oral contraception, but results of the current study are reassuring for non-diabetic women already receiving the shot or on the Pill, says Berenson. The Texas investigators hope to pursue additional research on the topic, she says.
Check the results
To conduct the longitudinal study, researchers measured fasting glucose and insulin levels in 703 white, African-American, and Hispanic women.
After counseling on the different types of contraception available and their efficacies, women were allowed to select one of three types of birth control: 245 selected an oral contraceptive (0.15 mg desogestrel plus 20 mcg ethinyl estradiol for 21 days, followed by two days of placebo and five days of 10 mcg ethinyl estradiol); 240 chose DMPA; and 218 chose a nonhormonal method. Women in the study also completed questionnaires containing demographic and behavioral measures every six months.
Researchers report that DMPA users, but not Pill users, experienced slightly greater increases in glucose and insulin as compared with nonhormonal users (P<.001). Among DMPA users, a small but steady increase in serum glucose levels (2 mg/dL at six months to 3 mg/dL at 30 months) was observed throughout the first 30 months, but it leveled off after that time. In contrast, serum insulin levels showed an upward trend (three units at six months to four units at 18 months) for the first 18 months of DMPA use; it then remained almost flat thereafter. Elevation of insulin and glucose levels was slightly more pronounced in obese and overweight DMPA users than those who were of normal weight.
These observed increases, which were less than those reported in previous studies,4,5 were not significant enough to cause concern, researchers report.
The Texas study adds solid evidence to the emerging body of research regarding contraceptives' impact on carbohydrate metabolism. In a 2007 Cochrane Review on the effect of steroidal contraceptives' impact on carbohydrate metabolism in women without diabetes mellitus, investigators concluded that such methods have limited effect on metabolism in non-diabetic women.6
While the reviewers noted the available evidence suggested that hormonal contraceptives have limited effect on carbohydrate metabolism in women without diabetes, they noted that strong statements could not be made due the small number of studies that compared any particular types of contraceptives.
Many trials had small numbers of participants and some had large losses, investigators said. Many studies had poor reporting of methods, and no information was available regarding the effects among women who were overweight, they state.6
In performing their data analysis, investigators did a computer search for studies of birth control methods containing hormones and how carbohydrates are handled in the body. Outcomes were glucose or insulin levels in the blood. Birth control methods included types with estrogen and progestin or progestin-only options. Types of birth control included in the review were pills, shots (injections), implant, the vaginal ring, and an intrauterine device. To undertake the review, investigators included randomized trials in any language that had at least three treatment cycles. Studies included in the review had to compare two types of birth control, or one type of contraception with a placebo method.
Investigators found 43 trials that met the inclusion criteria; however, no study stratified by body weight (normal weight versus overweight women). While results for desogestrel often were favorable regarding carbohydrate metabolism, investigators found they were inconsistent overall. Glucose and insulin means were more favorable for norethisterone in studies of progestin-only contraceptives. For other progestins, little or no difference was noted across trials, investigators reported.6
References
- Berenson AB, van den Berg P, Williams KJ, et al. Effect of injectable and oral contraceptives on glucose and insulin levels. Obstet Gynecol 2011;117:41-47.
- Dorflinger LJ. Metabolic effects of implantable steroid contraceptives for women. Contraception 2002;65:47-62.
- Kahn HS, Curtis KM, Marchbanks PA. Effects of injectable or implantable progestin-only contraceptives on insulin-glucose metabolism and diabetes risk. Diabetes Care 2003; 26:216-225.
- Fahmy K, Abdel-Razik M, Shaaraway M, et al. Effect of long-acting progestagen-only injectable contraceptives on carbohydrate metabolism and its hormonal profile. Contraception 1991;44:419-430.
- Vermeulen A, Thiery M. Hormonal contraceptives and carbohydrate tolerance. II. Influence of medroxyprogesterone acetate and chronic oral contraceptives. Diabetologia 1974; 10:253-259.
- Lopez LM, Grimes DA, Schulz KF. Steroidal contraceptives: effect on carbohydrate metabolism in women without diabetes mellitus. Cochrane Database of Systematic Reviews 2009. Doi:10.1002/14651858.CD006133.pub3.
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