What is Progesterone?

Fertility and menstruation are largely controlled by hormones, and one of these hormones is progesterone. Understanding progesterone and what it does will help women make informed choices about their reproductive health.

Progesterone is one of the progesterone steroid hormones. It is secreted by the corpus luteum, a temporary endocrine gland that the female body produces after ovulation during the second half of the menstrual cycle.

What does progesterone do?

Progesterone prepares the endometrium for the potential of pregnancy after ovulation. It triggers the lining to thicken to accept a fertilized egg. It also prohibits the muscle contractions in the uterus that would cause the body to reject an egg. While the body is producing high levels of progesterone, the body will not ovulate.

If the woman does not become pregnant, the corpus luteum breaks down, lowering the progesterone levels in the body. This change sparks menstruation. If the body does conceive, progesterone continues to stimulate the body to provide the blood vessels in the endometrium that will feed the growing fetus. The hormone also prepares the limit of the uterus further so it can accept the fertilized egg.

Once the placenta develops, it also begins to secrete progesterone, supporting the corpus luteum. This causes the levels to remain elevated throughout the pregnancy, so the body does not produce more eggs. It also helps prepare the breasts for milk production.

Potential Problems With Progesterone Production

Women who have low levels of progesterone will have abnormal menstrual cycles or may struggle to conceive because the progesterone does not trigger the proper environment for a conceived egg to grow. Women who have low progesterone levels and who do succeed in getting pregnant are at higher risk for miscarriage or pre-term delivery, because the hormone helps maintain the pregnancy.

Signs of low progesterone include:

• Abnormal uterine bleeding
• Irregular or missed periods
• Spotting and abdominal pain during pregnancy
• Frequent miscarriages

In addition, low progesterone levels can cause too-high levels of estrogen, which can decrease sex drive, contribute to weight gain, or cause gallbladder problems.

Questions to ask your doctor

For women who are struggling to conceive or carry a pregnancy, the emotional toll of the struggle is high. While you need to pursue every potential cause of this problem, it's valuable to talk to your doctor about your progesterone levels. If this is the problem, treatment is not difficult, but you should talk to your doctor before starting supplementation. Consider asking these questions:

• How can I determine if I am suffering from low progesterone levels?
• What other conditions could be causing my symptoms?
• How can I treat low progesterone levels?
• If I take supplemental progesterone, how long should I take it or when should I stop taking it?