The content of progesterone was determined in the peripheral venous blood of pregnant women from the 11th week after the last menstrual period up to the day of birth. There was a steady increase in the blood level from the 11th to the 35th week, but thereafter the level rose more rapidly, and remained high during labour itself. The significance of this rise after the 35th week is not fully understood. It may reflect a decrease in the rate of progesterone metabolism which occurs at this time. The blood level in three cases of twin pregnancy tended to be higher than the corresponding levels for single pregnancies. After removal of the placenta during elective caesarean sections, it was found that the blood progesterone level rapidly fell below the limits of sensitivity of the method. It has been estimated that the half-life of progesterone in the circulating blood must be 5 min or less.
PMID 14446187 14446187 DOI 10.1677/joe.0.0180418 10.1677/joe.0.0180418
Cite this article
Short, R. V., & Eton, B. (1959). Progesterone in blood. III. Progesterone in the peripheral blood of pregnant women. The Journal of endocrinology, 18(4), 418-425. https://doi.org/10.1677/joe.0.0180418
Short RV, Eton B. Progesterone in blood. III. Progesterone in the peripheral blood of pregnant women. J Endocrinol. 1959;18(4):418-425. doi:10.1677/joe.0.0180418
Short, R. V., and Bruce Eton. "Progesterone in blood. III. Progesterone in the peripheral blood of pregnant women." The Journal of endocrinology, vol. 18, no. 4, 1959, pp. 418-425.
Plasma levels of progesterone* were measured during normal human pregnancy by a sensitive and rapid competitive protein binding technique. During the first half of gestation 440 determinations in 321 women and in the second half of gestation, 209 determinations in 160 women were performed.
The average plasma level of progesterone in the 5th week of gestation was 24.8 ± 7.3 (s) ng/ml which is above the normal range of the luteal plateau of the menstrual cycle (10–20 ng/ml). Between the 5th and the 9th week of gestation the plasma concentration decreased significantly. From the 9th to the 32nd week of gestation the plasma level of progesterone increased from 16.7 ± 7.4 (s) to 125.2 ± 37.9 (s) ng/ml. During the last 8 weeks of gestation the plasma levels of progesterone did not show any significant rise. One woman was followed up from the day of ovulation to the 8th week of gestation. An increase in progesterone levels was observed about 10 days after ovulation. Morning samples of progesterone, which were taken before the 20th week of gestation, when the woman was still in bed, were found to be somewhat higher than levels found during the remainder of the day.
Progesterone concentrations in a few abnormal pregnancies are also reported.
The plasma concentrations of medroxyprogesterone acetate (MPA) in 14 women administered the progestagen for threatened abortion during the first 6 weeks of pregnancy were measured by specific radioimmunoassay. Treatment (52 nmol orally every 6 h) was continued to 18 weeks of gestation. The mean plasma concentration of MPA rose rapidly during day 1 of treatment to 14.1 +/- 1.84 nmol/l. It reached 21.5 +/- 2.3 nmol/l by 7 days and subsequently stabilized at around 26.8 +/- 5.0 nmol/l by the end of week 2. Urinary steroid profiles were determined by gas-liquid chromatography and mass spectrometry for six of the MPA-treated women and compared with those of six untreated women of similar gestational age. No differences were detected between the two groups of women, suggesting that the administration of MPA during pregnancy did not alter qualitatively or quantitatively the metabolism and excretion into urine of progesterone and oestrogens.
Reproductive EndocrinologyEmbryo Development EffectsIn Vitro Embryo CultureIn Vitro Studies
SUMMARY 1. The action of progesterone on the development of the mouse ovum from the eight-celled stage to the blastula has been studied in vitro . 2. Concentrations of progesterone below 2 μg/ml. produced no observable effect, whereas some toxicity was observed at 4 μg/ml. and few ova survived higher concentrations. 3. Herniation of the zona pellucida by the developing blastula is described; this process was inhibited by 4 μg/ml., but not by 2 μg/ml. of progesterone. 4. Blastulae appear to be more sensitive to the action of progesterone than are earlier stages. 5. Oestrogens afforded no demonstrable protection against the toxic action of progesterone when added to the culture medium. 6. The possible physiological significance of these findings is discussed.