Progesterone is an essential hormone for reproductive health. It prepares your body for pregnancy and plays a key role in several bodily functions. While the primary role is preparing your body for pregnancy, progesterone also helps regulate your menstrual cycle and even influences your mood.
Understanding how this hormone works is important for any woman, especially those navigating fertility challenges or hormonal health issues.
What Is Progesterone?
We often talk about the importance of estrogen for fertility and overall health, but there’s another vital hormone we shouldn’t disregard: progesterone.
Progesterone plays a central role in reproductive health. It’s primarily produced in the ovaries and has several important functions: regulating the menstrual cycle, supporting early pregnancy, and maintaining a healthy uterus. It also plays a role in cognition, particularly in women, where it affects our nervous system.
As women age and enter menopause, progesterone levels naturally decrease along with estrogen, which can affect overall hormonal balance. However, women and people with male sexual reproductive organs also have progesterone, albeit in smaller amounts. In males, it aids in sperm production and supports the development of male hormones.
Progesterone vs. Estrogen
If you’ve ever taken hormonal birth control, like the pill, chances are you’ve heard about progesterone and estrogen working together. They are similar in that both are key players in reproductive health, but that’s where the similarity ends. Estrogen is responsible for developing secondary sexual characteristics like breasts and managing the onset of menstruation. Progesterone stabilizes the menstrual cycle and prepares the body for pregnancy.
Estrogen is also involved in the menstrual cycle, pregnancy, and menopause, where it works in tandem with progesterone. Together, these hormones maintain balance in your reproductive system, ensuring that each stage of the cycle proceeds smoothly.
What Are the Functions of Progesterone?
Progesterone is mainly produced by the corpus luteum, a temporary mass of cells that forms in the ovaries after an egg is released. Its primary function is to prepare your uterus for a possible pregnancy. If fertilization occurs, progesterone thickens the uterine lining, allowing a fertilized egg to implant and begin growing. If the egg isn’t fertilized, the corpus luteum stops making hormones after about 14 days, and you have a period.
In the early stages of pregnancy, the adrenal glands and placenta produce progesterone in smaller amounts, contributing to maintaining a supportive environment for pregnancy.
During the Menstrual Cycle
Progesterone levels fluctuate throughout the menstrual cycle. About halfway through the cycle, a spike in the luteinizing hormone triggers ovulation. Progesterone production helps prepare the uterus for a potential pregnancy by thickening the uterus lining, among other things. The goal is to create the perfect environment for a fertilized egg to implant.
During Pregnancy
There’s a reason progesterone is widely known as the “pregnancy hormone.” If an egg is fertilized, the corpus luteum will continue producing progesterone, vital to support early pregnancy. Progesterone stimulates blood vessels in the uterine to support early fetal development. As the pregnancy progresses, the placenta takes over progesterone production, keeping hormone levels elevated during pregnancy. The hormone also eventually triggers lactation.
In Males
The adrenal glands produce progesterone in males, which has the primary function of supporting sperm production. Though present in smaller quantities than in women, it is still a vital hormone for reproductive health in men.
How Is Progesterone Controlled?
During the menstrual cycle, a surge in the luteinizing and follicle-stimulating hormones triggers progesterone production in the corpus luteum. After an egg is released, the corpus luteum forms and secretes progesterone, preparing the uterus for pregnancy.
If fertilization doesn’t occur, the corpus luteum disintegrates, leading to a progesterone drop, triggering your period. However, if fertilization happens, the embryo releases another hormone called human chorionic gonadotropin (hCG), keeping the corpus luteum intact and maintaining progesterone levels until the placenta takes over hormone production.
Why Are Progesterone Levels Tested?
Your healthcare provider may test your progesterone levels due to its importance in pregnancy and hormonal balance. Progesterone is crucial for maintaining the uterus during pregnancy, and low levels of this hormone are linked to higher risks of miscarriage and pre-term labor. Your healthcare provider may test your progesterone levels for several reasons:
- To test for ovulation
- Assess early pregnancy health
- Investigate the potential causes of uterine bleeding
- Monitor high-risk pregnancies
- Diagnose adrenal disorders
What Is Considered a Normal Progesterone Level?
Progesterone levels fluctuate throughout your menstrual cycle, during pregnancy and postpartum. Normal levels are measured in nanograms per milliliter (ng/mL) and fluctuate depending on your cycle’s stage:
- Follicular stage: < 0.7 ng/mL
- Luteal stage: 2 to 25 ng/mL
- First trimester of pregnancy: 10 to 44 ng/mL
- Second trimester: 19.5 to 82.5 ng/mL
- Third trimester: 65 to 290 ng/mL
After menopause, levels are very low, less than (< 0.5 ng/ml). You should consult your healthcare provider if you have concerns about your progesterone levels.
What Causes High Progesterone?
There are several reasons for elevated progesterone levels–some of them are normal, such as during certain phases of the menstrual cycle and pregnancy. However, persistent elevated progeserone levels aren’t normal and could signal a serious issue, such as:
- Ovarian cysts
- Adrenal ssues like adrenal cancer or adrenal hyperplasia (CAH)
- Ovarian cancer
- A rare condition called a “molar pregnancy,” when the fertilized egg implants incorrectly and abnormal cells or flud-filled sacs grow instead, mimicking pregnancy symptoms like nausea
What Are the Effects of High Progesterone?
High progestrone levels are normal during pregnancy and critical for a healthy pregnancy. The hormone is also usually present in hormona contraception.
What Causes Low Progesterone?
As with any hormonal imbalances, low progesterone levels can be detrimental to your health. If your levels are too low during pregnancy, it can cause several problems including miscarriage. The causes of low progesterone levels include:
- Anovulation (failure to release an egg)
- Reproductive conditions like Polycystic ovary syndrome (PCOS) or Endometriosis
- High stress levels
- Hypothyroidism (underactive thyroid)
- Hyperprolactinemia (excess prolactin production)
- Low cholesterol
- Perimenopause
- Overexercising or extreme dieting
What Are the Effects of Low Progesterone?
Low progesterone can make it difficult conceive and cause pregnancy complications. You may also have other physical and psychological symptoms like:
- Issues maintaining a healthy weight
- Bloating
- Fatigue
- Low libido
Fertility Problems and Progesterone Tests
Ify you’re having issues conceiving, your healthcare provider may order a number of tests, including progesterone. Low progesterone levels may signal anovulation, meaning you’re ovulating ireregularly or not at all. Anovualtory inferilty is the most common form of infertility, accounting for 30% of cases.
Other signs of low progesterone include irregular periods, spotting during pregnancy, and repeated miscarriages. Low progesterone can also lead to excess estrogen, which may reduce libido and cause weight gain.
Progesterone is more than just a hormone—it’s a key player in your reproductive health and overall well-being. Understanding its role can help you stay proactive in managing your hormonal health, particularly when it comes to fertility and pregnancy.
To support balanced hormonal health, focus on maintaining a nutrient-rich diet, staying active, and considering a daily women's health multivitamin to fill any nutritional gaps.
