Plasma human chorionic gonadotropin, estrone, estradiol, estriol, progesterone, and 17α-hydroxyprogesterone in human pregnancy: III. Early normal pregnancy

Abstract

The concentrations of human chorionic gonadotropin (HCG), progesterone (P), 17α-hydroxyprogesterone (17-OHP), and unconjugated estrone (E1), estradiol (E2), and estriol (E3) were measured by radioimmunoassay in plasma of 10 patients followed from the third to the thirteenth week of pregnancy. Up to the fifth week of pregnancy, an increase in the mean plasma concentration of E1, E2, P, and 17-OHP was observed. After the fifth week of pregnancy, however, only the mean plasma concentration of E1 and E2 continued to increase, whereas that of 17-OHP started to decrease and that of P remained unchanged until the tenth week of pregnancy. Unconjugated E3 became detectable (> 50 pg. per milliliter) only after the ninth week of pregnancy, after which its level continued to increase gradually. The mean HCG plasma level increased until the tenth week of pregnancy, after which it began to decline. No correlation was found between HCG and E2 or HCG and P plasma concentrations, but good correlation was found between E1 and E2 levels. The mean P plasma concentrations between the third and the fifth weeks of pregnancy was about 100 times higher than that of E2. By the thirteenth week of pregnancy, however, the mean P/E2 ratio had decreased sixfold, reaching a ratio similar to that observed at the second half of pregnancy. Most levels of P, E1, and E2 up to the seventh week of pregnancy were in the range found during the menstrual period. During the first 7 weeks of pregnancy, the diagnosis of intrauterine pregnancy cannot be made with certainty by determination of any of these steroid hormones.