Higher estrogen levels during pregnancy in Andean than European residents of high altitude suggest differences in aromatase activity

Abstract

Context: Uteroplacental hypoxia has been reported to lower estrogen levels in preeclampsia as the result of reduced aromatase activity. Objective: We asked whether the chronic hypoxia of residence at high altitude in the absence of preeclampsia lowered estrogen, whether such effects differed in Andean vs European high-altitude residents, and whether such effects were related to uterine artery diameter or blood flow. Design, Setting, and Participants: Studies at weeks 20 and 36 of pregnancy were conducted in 108 healthy Bolivian low- (400 m, n = 53) or high-altitude (3600 m, n = 55) residents of European (n = 28 low and 26 high altitude) or Andean (n=25 low and 29 high altitude) ancestry. All groups were similar in age, nonpregnant body mass index, and pregnancy weight gain. Results: High-altitude residence increased circulating progesterone, cortisol, estrone, 17β-estradiol, and estriol levels (all P < .01). High-altitude Andeans vs Europeans at week 36 had higher progesterone, estrone, 17β-estradiol, and estriol levels as well as product to substrate ratios for the reactions catalyzed by aromatase, whereas week 36 cortisol levels were greater in the European than Andeanwomen(all