Progesterone is a steroid hormone released in the ovaries, and is necessary for the implantation of the fertilized egg in the uterus and maintaining pregnancy. Progesterone is also used to regulate abnormal menstrual cycles and helps kickstart menstrual cycles that have abruptly stopped (known as amenorrhea).

What is progesterone?

Progesterone is a hormone made by the adrenal gland, the ovaries, and the testicles. It plays an important role in reproduction for all sexes.

Progesterone and male fertility

Progesterone is necessary for sperm production and maturation as well as testosterone production. Progesterone is actually a building block for testosterone, so levels that are too low can lead to testosterone deficiency.

But too-high levels of progesterone can inhibit sperm production. Research actually shows that progesterone may be effective as birth control for people with sperm, though this is not yet available.

Blood progesterone levels are usually below 3.18 nmol/L in healthy cis males.

Progesterone and female fertility

Progesterone plays a key role in pregnancy and fertility, including: 

• preparing the uterus for an egg
• blocking milk production by the breasts until after pregnancy
• maintaining normal levels of other reproductive hormones, such as estrogen

If you’re experiencing infertility, your doctor may order a progesterone blood test. Levels of progesterone should spike after ovulation, so monitoring this hormone can help confirm that a patient successfully ovulated. Progesterone may also be monitored throughout pregnancy. Progesterone levels will vary based on the stage of the menstrual cycle and whether someone is pregnant or in menopause.

High progesterone levels can indicate successful ovulation or pregnancy (as pregnant people have approximately 10 times higher levels of progesterone). Excessively high progesterone levels may indicate an ovarian cyst or ovarian cancer. Low progesterone levels increase the chance of preterm birth and miscarriage, and are linked to reduced fertility.

Progesterone (also called progestin) can be used as a form of birth control, such as “the pill.” Progesterone hormone replacement therapy may be prescribed if: 

• you stopped having your period, but haven’t yet reached menopause
• you’re treating menopause symptoms
• you have endometriosis pain
• you’re at risk of delivering early or having a miscarriage