Hormonal Contraception, Body Water Balance and Thermoregulation
Annual rept. 15 Sep 97-14 Sep 98
JOHN B PIERCE FOUNDATION LAB NEW HAVEN CT
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To test the hypothesis estrogen enhances water and sodium retention, we compared the fluid regulatory responses to 150 mm of exercise-induced dehydration, followed by 180 ruin of ad libitum drinking during the follicular and luteal phases of the menstrual cycle, and following treatment with an estrogenprogestin OC EP and a progestin-only OC P oral contraceptive in a double-blind, randomized, cross-over design. We found a downward shift in osmotic regulation of arginine vasopressin AVP during the luteal phase and OC EP compared to the follicular phase during exercise. This shift was not accompanied by plasma volume expansion or fluid retention. Fluid and electrolyte losses during exercise were attenuated during the follicular phase of the menstrual cycle, but overall fluid and electrolyte balance was similar across all trials. We also determined that the variability of the fluid regulatory hormones renin, aldosterone and atrial natriuretic peptide was high over the course of two menstrual cycles, but slopes and intercepts defining osmotic regulation of AVP were highly reliable. We are in the process of examining the impact of estrogen and progesterone on thermoregulation, although due to our double-blind design, we have no comment on the effects of the oral contraceptives at this point. Preliminary data on 3 women who have completed testing in both menstrual phases reveal no effect of menstrual phase on basal or exercise core or skin temperature, although sweating is attenuated during the luteal phase.
- Medicine and Medical Research