LOW SERUM ESTRADIOL AND HIGH SERUM PROGESTERONE CONCENTRATIONS CHARACTERIZE HYPERTENSIVE PREGNANCIES AT HIGH-ALTITUDE

OBJECTIVE: Intrauterine growth retardation and preeclampsia ape more c ommon at high than at low altitude. Because altered hormonal profiles have been linked with these disorders, we asked whether placental ster oid hormone concentrations were altered during pregnancy at high altit ude. METHODS: We measured progesterone, unconjugated estradiol, and es triol (by radioimmunoassay) at weeks 20, 30, and 36 of pregnancy in 18 women at low altitude (1600 mj and 40 women at high altitude (3100 m) . RESULTS: Women at 3100 m compared with 1600 m had lower serum estrad iol concentrations at week 36 of pregnancy, and lower estriol and high er progesterone concentrations throughout pregnancy, ils a result, the progesterone/estradiol ratio was greater in the high- versus the low- altitude women. Estradiol fell between weeks 30 and 36 in women who de veloped transient hypertension or preeclampsia. The fall in estradiol was accompanied by a marked increase in progesterone concentrations am ong the preeclamptic women. At 3100 In, estradiol correlated negativel y (r = -0.37, P < .05) and progesterone positively (r = 0.46, P < .05) with mean arterial pressure at week 36 of pregnancy. CONCLUSIONS: We speculate chat reduced placental oxygen pressure (PO2) at high altitud e may decrease placental aromatase activity and thereby lower estradio l and estriol concentrations. The factor(s) responsible for the vise i n progesterone is unknown. Possibly, high progesterone relative to est radiol concentrations contributes to the development of preeclampsia a t high altitude.