Progesterone and Progestins

Fertility and menstruation are largely controlled by hormones, and one of these hormones is progesterone. Progesterone is a steroid hormone belonging to a class of hormones called progestogens. 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.

Synthetic steroid hormones with progesterone-like properties are called progestins. Progestin is often combined with estrogen, another hormone, to develop contraceptives such as birth control pills and skin patches. Progestin is also useful in treating common menopausal symptoms. Understanding progesterone and progestins will help women make informed choices about their reproductive health.

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.

What Does Progestin Do?

Progestins were created to bind to progesterone receptors in the body and create similar effects as progesterone. Progestin can change the lining of the uterus and stop the lining from building up. Scientists made progestin because progesterone isn’t absorbed well when taken as a pill.

Progestin can also be used to treat menopause symptoms such as hot flashes and vaginal dryness. Estrogen can be used alone to treat these symptoms, or it can be combined with progestin.For women who are perimenopausal or newly menopausal, healthcare providers may suggest an oral micronized progesterone treatment.

Progestin can also be prescribed to treat amenorrhea, endometriosis, and irregular periods.

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.

What Problems Can Occur with Progestin?

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.

If you are taking progestin to treat menopausal symptoms, for birth control, or to treat other conditions side effects may occur. Side effects may occur due to the dosage of progestin, how progestin interacts with hormone receptors, and your body’s response to progestin.

When taking progestin for menopausal symptoms, side effects may include mood changes, bloating, headaches, and breast tenderness. For newly menopausal women, breakthrough bleeding may occur.

In hormonal birth control, progestin side effects can include withdrawal bleeding and increased cramping. Other side effects may include an increased blood pressure and low blood sugar.

Questions to Ask Your Healthcare Team

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?
• Am I a candidate for menopausal treatment therapy?
• Am I at risk for any side effects?
• Which hormonal birth control method should I use?