What is progesterone?
Progesterone is an important hormone in the female reproductive system. It is sometimes called the “pregnancy hormone” because it plays a major role in pregnancy.
Some key points about progesterone:
- Progesterone is produced mainly by the corpus luteum in the ovary during the second half of the menstrual cycle. The corpus luteum forms after an egg is released from the ovary.
- It helps prepare the uterus for pregnancy. Progesterone causes the lining of the uterus to thicken to support a fertilized egg.
- If pregnancy occurs, progesterone helps maintain the pregnancy by supporting the uterine lining. The placenta starts producing more progesterone in early pregnancy.
- If pregnancy does not occur, progesterone levels will decrease sharply, leading to menstruation.
- Progesterone also helps prepare the breasts for lactation and breastfeeding.
In summary, progesterone has several important reproductive functions:
- Preparing a thick, vascularized uterine lining that can support embryo implantation
- Maintaining the uterus supportive to pregnancy in early stages before placental progesterone production picks up
- Supporting healthy pregnancy and fetal development
- Preparing mammary glands for lactation
When are progesterone levels checked?
Doctors may check progesterone levels in different situations related to a woman's reproductive health or ability to get pregnant.
Some examples include:
- To evaluate possible causes of infertility or miscarriage risk
- To check if ovulation occurred
- To monitor hormone replacement therapy
- To check placental health during high-risk pregnancies
What are progesterone supplements?
Progesterone supplements, such as pills, vaginal gels or suppositories, may be prescribed for different reasons:
- To support pregnancy in women with luteal phase defects
- To mimic normal hormonal cycles in transgender women
- To treat secondary amenorrhea or abnormal uterine bleeding
- As hormone therapy in peri- and post-menopausal women
It’s important to take progesterone only under the supervision of a doctor, who can prescribe the appropriate type, dose, and timing of supplementation tailored to your needs.
Over-the-counter “progesterone creams” are also popular, but evidence on their efficacy is lacking. The best approach is to have your hormone levels properly tested and use bioidentical progesterone prescriptions when truly indicated.