Progesterone is a steroid hormone produced by the corpus luteum ovarian cells, and by the placenta during pregnancy. Progesterone concentration shows high correlation with the development and regression of the corpus luteum. While progesterone is slightly detectable in the follicular phase, an increase in the level of progesterone the day before ovulation can be noticed. Increased synthesis of progesterone is maintained during the luteal phase.
Determination of the level of progesterone is the best test to confirm the occurrence of ovulation. In the second half of the cycle pregnanediol is eliminated in the urine as the main degradation product of progesterone. During pregnancy there is a progressive increase in progesterone levels between weeks 9 and 32, often 100 times compared to what it was before pregnancy. Progesterone concentration is higher in case of multiple pregnancies compared to single pregnancy situations.
The uterus is the most important target-organ of progesterone. Progesterone performs a transformation of the uterine lining tissue rich in glands (secretory phase), which will favor the implantation of the fertilized egg womb. During pregnancy progesterone inhibits contractions of myometrium, but decreases sensitivity to physiological stimuli of contraction. In mammary glands progesterone (together with estradiol) stimulates proliferation and secretory alveoli arrangement.
Recommendations for progesterone determination
In women: detection ovulation and tracking the luteal phase, establishing the functional status of the corpus luteum formation, determining the functional status of patients with infertility, functioning of the placenta during pregnancy, ovarian function testing, ovarian tumors, ovarian cysts, impending abortion, fetal death , toxemia of pregnancy. Serum progesterone together with beta-HCG allow differentiation of normal uterine pregnancy from ectopic pregnancy or abnormal uterine pregnancy.
Reference values - are dependent on age and sex, and women and the menstrual cycle:
• prepuberty : 0.3-1.8 nmol / L;
• First trimester of pregnancy: 32.6-140 nmol / L;
• Second trimester of pregnancy: 62-262 nmol / L;
• Third trimester of pregnancy: 206.7-728 nmol / L.
Conversion factors: nmol / L x 0.314 = ng / mL; ng / mL x 3.18 = nmol / L.
Critical values – <16 nmol / L: load unviable; 16-32 nmol / L: pathological pregnancy.