Progesterone

Progesterone is one of the main female reproductive hormones, responsible for regulating the menstrual cycle and supporting pregnancy. Its levels in the blood vary throughout each menstrual cycle and drop when a woman goes through menopause, and her periods stop. 1

Imbalances in progesterone levels can be caused by different health problems, and manifest in various ways. Low progesterone symptoms include irregular periods, spotting between periods, difficulty becoming pregnant, and a reduced sex drive. 2

Hormone supplements are available to some women whose progesterone levels are found to be low.

Progesterone belongs to a group of hormones called ‘progestogens’. It plays an important role in controlling the female reproductive cycle together with other hormones such as estrogen, luteinizing hormone (LH) and follicle-stimulating hormone (FSH).

When an egg (ovum) becomes released during ovulation, it leaves behind the follicle within which it matured. This follicle, now called the ‘corpus luteum’, starts producing and secreting progesterone. However, progesterone is also produced in other organs and tissues, such as the adrenal glands, ovaries, or placenta. 3 4

Progesterone acts on the lining of the uterus, making it thicker. This happens so that, if the ovum becomes fertilized, the uterus can support a pregnancy. If fertilization does not occur, the corpus luteum stops producing progesterone. When this happens the lining of the uterus starts to shed, and you get a period. 3

If you become pregnant progesterone levels stay high and continue to rise, supporting the growing fetus. Additionally, it promotes the development of milk glands. It is very important that its levels remain appropriately elevated, as low progesterone during pregnancy can cause premature births, or even miscarriages. 4 5

Progesterone is also commonly used as an oral contraceptive; either on its own, or in combination with estrogen. Progesterone-only pills act by increasing the mucus lining of the cervix, which in turn forms a barrier that sperm cannot penetrate through. 5

Progesterone levels will be different depending on what phase of the menstrual cycle you are in. They are low during the first half of your menstrual cycle, or what is called the ‘follicular phase’. They then rise steeply after ovulation, during the ‘luteal phase’, and drop again right before your period starts. 5

The National Health Service (NHS) in the UK has published the following reference ranges for progesterone levels: 6

• Days 1-14 (Follicular phase): <5.0 nmol/L
• Days 14-28 (Luteal phase): 3.5-67 nmol/L

After you go through the menopause, your progesterone levels drop and stabilize at <4.4 nmol/L. This is a normal and natural process. 1 6

If you find that you are experiencing symptoms of low progesterone, you might want to get your levels checked. Progesterone levels are also tested during pregnancy, as they are important to the development of the fetus. 5 Women who are having difficulty conceiving or have had a miscarriage might also benefit from this test.

Because it is produced by the corpus luteum, progesterone levels can be checked to confirm that you have ovulated that month. 4 This is easily done with a blood test around day 21 of your menstrual cycle, when your progesterone is at its highest level. 1 Of course, every woman’s cycle is different, so the best time to do this test should be discussed with a health professional beforehand.

If your test comes back indicating low progesterone levels, there may be a few reasons for this. Menopause, polycystic ovary syndrome (PCOS), and insufficient progesterone production by the reproductive system, also called ‘luteal phase deficiency’, are some possible causes. 7 You can read more about different menstrual disorders here.

Like lots of other hormones in your body, progesterone is affected by your diet and lifestyle. Building certain habits into your daily life or changing your diet may therefore help increase your progesterone levels. Some possible modifications are: 8

• Maintaining a healthy weight
• Exercising regularly, but not excessively
• Eating a varied and healthy diet
• Limiting stress

The Mediterranean diet in particular has been recommended for keeping hormones in balance. This type of diet is rich in vegetables, fish, whole grains, nuts, legumes, and healthy oils. 8

If you are diagnosed with low progesterone, your healthcare provider may also decide to prescribe you progesterone supplements. This is a synthetic form of the hormone that helps restore target progesterone levels in your body.

Supplements not only improve the symptoms of low progesterone in menopause or luteal phase deficiency, but can help you become pregnant, and prevent miscarriages. You might also receive progesterone supplements if you are receiving IVF, or other assisted reproductive technology (ART) treatment. 7

Currently, progesterone supplements are available mainly as pills, creams, or suppositories. 9

These are taken by mouth, usually between days 15 and 26 of your menstrual cycle. They should be taken before going to bed.

These are inserted into the vagina daily. Your doctor will discuss dosing and frequency with you.

These are also inserted into the vagina, with the help of an applicator. They are taken between days 18 and 21, and absorbed through the skin.

Pessaries are a less commonly prescribed form of progesterone supplementation. These are small devices which are placed inside the vagina, and gradually release progesterone over time. 9

Progesterone supplements are generally safe and well-tolerated, but some people may experience certain unwanted effects when taking them. Common progesterone side effects include: 5 9

• Headaches
• Irregular periods
• Sore breasts
• Stomach upset
• Drowsiness
• Blood hypercoagulability

Q: How long after taking progesterone will I get my period?
A: You will get your period after you finish your course of supplements. This usually happens 1-3 days after your last dose.

Q: Which type of progesterone supplement would be best for me?
A: The type of supplement that is best suited to your needs varies between individuals. It is best to talk about this with your healthcare professional.

Q: How long does it take for progesterone cream to work?
A: It might take a few months for you to notice an improvement in your symptoms. More research on this topic is still needed.