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Circadian Rhythms of Serum and Urinary Estrogens in Pregnancy¹

JOHN D. TOWNSLEY^*, NORMAN H. DUBIN, GEORGE F. GRANNIS, LINDA J. GARTMAN^* and C. DEANS CRYSTLE^*

^* Pregnancy Research Branch, National Institute of Child Health and Human Development, National Institutes of Health Bethesda, Maryland 20014
Department of Obstetrics and Gynecology, University of Maryland Baltimore, Maryland 21201
Department of Pathology, Ohio State University Columbus, Ohio 43210

¹ Address reprint requests to Dr. John D. Townsley.

Diurnal variations in serum unconjugated estradiol-17β (SE₂), serum total estriol (SE₃), total urinary estrogens (UE), and UE/creatinine ratios (E/C) were determined on samples obtained at 4-hr intervals from 22 women in the third trimester of normal pregnancy. Analysis of variance indicated significant variations in SE₂ (p < 0.001), UE (p < 0.01), and E/C (p < 0.05). Multiple comparison of means showed maximum values at 12 PM to be significantly greater than minimum values at 12 AM (p < 0.01). The SE₃ rhythm was less marked with individual daytime (8 AM–12 PM–4 PM) means significantly greater (p < 0.001) than those at nighttime (8 PM–12 AM–4 AM). It is proposed that this rhythm reflects changes in availability of estrogen precursors known to be secreted rhythmically by the maternal adrenal.

Received June 5, 1972.