Definition - What does Progesterone mean?

Progesterone is a female hormone that regulates the menstrual cycle, prepares the uterus for implantation of the fertilized egg, and maintains a healthy pregnancy. Progesterone is produced by the ovaries after the ovulation, and the placenta during pregnancy. Progesterone levels change along the menstrual cycle; they start raising right before the ovulation (release of the egg from the ovary), and keep high for the following two weeks. Progesterone will thicken the endometrium to prepare the uterus for the possible implantation of a fertilized egg. If the egg is not fertilized, progesterone levels descend, the endometrium falls, followed by the menstruation.

FertilitySmarts explains Progesterone

When pregnancy occurs and the egg is fertilized, the ovaries will produce enough progesterone to assure a proper environment for the embryo in the uterus. After week eight the placenta is completely formed and will become the main producer of progesterone. The so-called "gestational hormone" is responsible for implantation of the fertilized egg, survival and development of the fetus during the entire pregnancy. Progesterone also stimulates the development of the glands in the breasts that are responsible for milk production.

In some cases, ovulation may be absent from the menstrual cycle. This is called an anovulatory cycle. This means that the follicles inside the ovaries will not develop, so the ovary will not produce enough progesterone to prepare the endometrium for a successful implantation of the fertilized egg. Women over mid-30s may have anovulatory cycles, and this missed ovulation may happen more often as they approach menopause.

Progesterone may be supplemented through a synthetic version when ovaries do not produce the hormone regularly, or in the necessary amount. Progesterone supplementation is key in fertility treatments such as in-vitro fertilization (IVF) because it supports implantation of the egg and and preserves pregnancy.

Effects of low progesterone include:

  • Irregular cycles due to missed ovulation
  • Uterine fibroids
  • Tenderness in breasts
  • Mood fluctuations
  • Heavy menstrual bleeding

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