Hormonal Contraception, Body Water Balance and Thermoreregulation
Abstract
To test the hypothesis that estrogen enhances water and sodium retention, we compared the fluid regulatory responses to 150 min of exercise-induced dehydration, followed by 180 min of ad libitum drinking during the follicular and luteal phases of the menstrual cycle, and following treatment with an estrogen/progestin (OC E+P) 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 E+P compared to the follicular phase during exercise, which was not accompanied by plasma volume expansion or fluid retention. 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 also determined the estrogen and progesterone on thermoregulation. We found that OC P increased core temperature and delayed the onset of sweating during exercise, but that OC E+ blocks these effects. This indicates that estrogen blocks the progestin-related changes in thermoregulation while on oral contraceptives. We also found that all of these effects were independent of changes in plasma volume. We have begun testing the impact of OC P and OC E+P on osmotic regulation of AVP during hypertonic saline infusion, but have completed only three subjects so have no comment at this point.
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 01, 1999
- Accession Number
- ADA381174
Entities
People
- Nina Stachenfeld