RENO, NEV. — Patients taking extended-cycle oral contraceptives experienced about the same number of total bleeding days over 6 months as women taking a standard, 28-day oral contraception regimen, but they had significantly fewer days of moderate to heavy bleeding, a new study indicates.
“There is lower serum and urinary estrogen, [as well as] smaller ovaries and follicles, thinner endometrium, and improved patient symptomatology with a continuous oral contraceptive pill regimen,” Dr. Richard S. Legro reported at the annual meeting of the Society for Gynecologic Investigation.
The findings support the use of extended cycle suppression with oral estrogen (20 mcg) and progestin norethindrone acetate (1 mg) in a continuous regimen for indications such as endometriosis, hirsutism, and acne, Dr. Legro said at the meeting, where he presented the findings in poster form.
No pharmaceutical companies contributed funding for the study, which was financed in part by the National Institutes of Health, said Dr. Legro, a reproductive endocrinologist at Pennsylvania State University in Hershey, Pa.
Dr. Legro and his coinvestigators enrolled 62 normally cycling women in a double-blind, randomized controlled trial and followed them for symptoms, bleeding patterns, endometrial histology, follicular development, and serum and urinary levels of sex steroids. The women either took the standard regimen of oral contraceptives for 28 days per month with the traditional 7-day pill-free interval or they took the contraceptives continuously.
Although the number of bleeding days was reduced in women on the continuous OC regimen, the difference was not statistically significant due to a rebound in bleeding days by the study's conclusion, explained Dr. Legro.
The number of moderate to heavy bleeding days dropped to 1 day/month or less by cycle 2 in the continuous OC group, decreasing more slowly over time in women taking the 28-day OC regimen.
“If you biopsy, you get absolutely nothing [in patients on the continuous regimen]. There is no endometrium there,” Dr. Legro said in an interview at the meeting.
He said breakthrough bleeding in these patients might be explained by endometrial atrophy due to ovarian suppression, whereas in the 28-day group there was evidence for rebound follicular activity and ovulation following the pill-free interval.
Women taking continuous OC pills had a 25%–30% greater suppression of serum estrogen levels than those on the 28-day regimen.
Total ovarian volume, maximum diameter of the largest follicle, and endometrial thickness were all reduced significantly more in patients on the continuous regimen.
Scores on premenstrual pain, behavior, and distress scales were also lower for women assigned to receive continuous OC pills.
No differences were found between groups in terms of safety on measures of blood pressure, glucose and insulin levels, liver and renal profiles, thyroid-stimulating hormone, or lipids.
In patients on the continuous regimen, there is no endometrium there when you biopsy. DR. LEGRO