Progesterone

Progesterone is a hormone that plays a major role in the female reproductive system. It supports your menstrual cycle and helps maintain the early stages of pregnancy.

Males have progesterone, too, but in much lower amounts. It aids sperm production and androgen hormone conversions.

Levels that are consistently low in females can lead to health issues, like irregular periods.

What are normal levels of progesterone?

In females, progesterone levels fluctuate throughout the menstrual cycle. Levels rise after ovulation, which is when your ovary releases an egg. They continue to rise if pregnancy occurs. The levels are highest in the third trimester (weeks 28 to 40 of pregnancy).

The levels decline in the years leading up to menopause, when ovulation stops.

Your healthcare provider is the best person to determine what your progesterone level should be. They consider your age, where you are in your menstrual cycle and whether you’re pregnant.

Progesterone as medication

Progestins are forms of progesterone made in a lab. They’re often combined with estrogen to develop birth control options like pills and skin patches. Progestin can also help manage menopause symptoms.

What does progesterone do?

The main function of progesterone is to prepare the lining of your uterus (endometrium) for a fertilized egg to implant and grow. If a pregnancy doesn’t occur, this lining sheds during your menstrual period. If conception occurs, the hormone increases to support the pregnancy.

Other roles include:

• Regulating bleeding during menstruation
• Regulating your mood
• Supporting thyroid function
• Supporting lactation

Progesterone may also help protect your central and peripheral nervous systems. Researchers are still learning about this function.

Progesterone and menstruation

Ovulation occurs around the middle of your menstrual cycle. A temporary gland called the corpus luteum forms from the empty egg follicle and begins making progesterone. The hormone thickens your uterine lining to create a healthy environment for a fertilized egg to implant.

If an egg isn’t fertilized during that cycle (meaning you don’t get pregnant), the corpus luteum breaks down. This decreases progesterone levels. Your uterine lining thins and breaks down, causing your period.

Progesterone during pregnancy

If a sperm cell fertilizes an egg, the corpus luteum continues making progesterone. This thickens your uterine lining even more to support the growing embryo. At around 10 weeks of pregnancy, the placenta takes over hormone production.

Levels continue to rise during pregnancy. High progesterone levels prevent your body from ovulating while you’re pregnant. This hormone also suppresses uterine contractions to help you avoid preterm labor. Finally, progesterone helps your breasts prepare for breastfeeding.

How does your body make it?

Three main tissues make progesterone:

• Corpus luteum: This makes progesterone each menstrual cycle and for the first 10 weeks of pregnancy.
• Placenta: This makes progesterone after about 10 weeks of pregnancy.
• Adrenal glands: These glands make a small amount of the hormone.

What are the common conditions associated with progesterone?

Low progesterone is the most common issue related to this hormone. It can cause health problems like:

• Irregular periods
• Decreased fertility
• Miscarriage
• Preterm labor (before 37 weeks of pregnancy)

In rare cases, high progesterone can be a sign of a type of ovarian tumor called a granulosa cell tumor.

Another related condition is progesterone receptor-positive breast cancer (PR-positive breast cancer). This cancer needs the hormone to grow.