Progesterone (P)

Progesterone is an important progestogen, belonging to steroid hormones, with a relative molecular weight of 314.5. It is mainly produced by the corpus luteum of the ovary and the placenta during pregnancy. It is the precursor of testosterone, estrogen and adrenal cortex hormones. The progesterone level produced during the follicular phase of normal males and females is very low, after secretion into blood, it is mainly bound to albumin and sex hormone binding protein and circulating in the body.

The main function of progesterone is to make the uterus prepared for the implantation of fertilized eggs and to maintain pregnancy. During the follicular phase of the menstrual cycle, the progesterone level is low. After ovulation, the progesterone produced by corpus luteum increases rapidly, and reaches the maximum concentration of 10ng/mL-20ng/mL in 5-7 days after ovulation. If not conceived, the corpus luteum atrophies during the last four days of the menstrual cycle and the progesterone concentration decreases to follicular phase. If conceived, the corpus luteum does not fade and continues to secrete progesterone, keeping it at levels equivalent to the medium luteal phase and continuing until the sixth week of pregnancy. During pregnancy, the placenta gradually becomes the main source of progesterone, and the concentration increases from 10ng/mL-50ng/mL in the first 3 months of pregnancy to 50ng/mL-280ng/mL in the 7-9 months. Clinical studies have shown that progesterone plays a role in promoting ovulation and maintaining the normal function of the corpus luteum in non-pregnant women. If the progesterone produced by corpus luteum is insufficient, it may indicate the corpus luteum function is insufficient, and the insufficient corpus luteum function is related to infertility and early miscarriage.