Objectives
To describe the effect of combined oral contraceptives (COC) on Matrix Metalloproteinase (MMP) -2 and -9 activity and compare MMP activity in women taking aCOC with or without doxycycline.
Study Design
Subjects (n=20) underwent endometrial biopsies1) in the late luteal phase of a baseline cycle prior to initiating COCs, 2) on day 19 to 21 while taking COCs in a standard 28-day cycle (7-day hormone free interval), 3) on day 26 to 28 while taking active COCs continuously for a 28 day cycle. During the continuous COC cycle, they were randomized to receive daily sub-antimicrobial dose doxycycline 40 mg or placebo.
Results
Compared to baseline, COC treatment increased MMP-2 (p<0.001) and -9(p<0.001). MMP activity was lower in subjects taking a COC with doxycycline compared to those receiving placebo, although only significantly lower for MMP-2LF (p=0.002).
Conclusions
Unscheduled bleeding with COCs may be the result of increased endometrial MMPs. Sample size limitations prevent us from determining how doxycycline affects MMP activity in COC-users.