RANDOMIZED COMPARISON OF ORAL AND TRANSDERMAL HORMONE REPLACEMENT ON CAROTID AND UTERINE ARTERY RESISTANCE TO BLOOD-FLOW

Objective: To compare the long-term effects of oral and transdermal ho rmone replacement therapy (HRT) on carotid and uterine vascular impeda nce. Methods: Sixty-three postmenopausal women were randomized to 1 ye ar's treatment with oral or transdermal sequential combined HRT. Carot id and uterine artery pulsatility indices (PIs) were assessed by color Doppler at baseline, and after 2, 6, and 12 months of treatment. Fift y-eight women completed the trial, 27 in the oral and 31 in the transd ermal group. In a subgroup of 30 women, we also performed Doppler meas urements in the estrogen-progestin combined phase. The study had 90% p ower to detect a difference between treatment groups of 0.05 in the ca rotid artery and of 0.25 in uterine artery PI at the 5% significance l evel. Results: The carotid PI decreased significantly (P < .001) and s imilarly during both regimens. This drop was already clearly detectabl e during the second month, from 0.97 (0.95, 1.01) (mean and 95% confid ence intervals [CI]) to 0.94 (0.91, 0.97) in the oral and from 0.98 (0 .94, 1.00) to 0.92 (0.89, 0.95) in the transdermal group, but it conti nued up to 12 months (0.85 [0.82, 0.88], 13% of baseline values in the oral group and 0.84 [0.81, 0.87], 14% in the transdermal group). In t he uterine arteries, the drop in PI was steeper and greater and reache d its maximum at 6 months (39% and 40%, respectively). Drops in caroti d and uterine PI correlated positively with baseline PI values, but we re not affected by patient age, time from menopause, previous HRT and smoking. Addition of norethisterone acetate did not counteract drops i n carotid and uterine PI in either group. Conclusion: Oral and transde rmal sequential HRT are similarly effective at 1 year in reducing impe dance to flow in carotid and uterine circulation. This long-term vascu lar effect might explain how HRT protects women from cardiovascular di sease. (Obstet Gynecol 1998;92:563-8. (C) 1998 by The American College of Obstetricians and Gynecologists.).