Written by Dr. Specialist Stine Andreasen
Specialist in Gynecology and Obstetrics, PhD in Obstetrics in 2015 and more than 15 years of clinical practice in Obstetrics and Gynecology
If you have a uterus and take estrogen as part of hormone therapy (HRT), you will usually also need progesterone or a similar hormone. Its main job in HRT is not to treat symptoms but to protect the lining of the uterus (the endometrium).
Read more → HRT for menopause – benefits and risks
Key takeaways
- In HRT, progesterone’s main role is to protect the endometrium from the stimulating effect of systemic estrogen.
- It is mainly relevant for women who still have a uterus.
- The options are micronized (body-identical) progesterone, synthetic progestogens in tablets or patches, and a 52 mg levonorgestrel intrauterine device.
- Sequential HRT gives a monthly withdrawal bleed and suits perimenopause. Continuous combined HRT aims for no bleeding and is generally preferred after periods have stopped..
- Persistent, heavy or new bleeding on HRT should always be checked by a doctor.
What does progesterone do?
Progesterone is produced by the ovaries after ovulation. During the reproductive years, it helps regulate the menstrual cycle and prepares the endometrium for a possible pregnancy. In perimenopause, ovulation becomes less predictable, so progesterone levels may fall or fluctuate.
Why do you need progesterone with estrogen in HRT?
Systemic estrogen stimulates the endometrium to grow. Without enough progesterone or another progestogen, the endometrium can become too thick, which increases the risk of endometrial hyperplasia and endometrial cancer. Adding progesterone or another progestogen protects against this.
The dose and duration must be enough to protect the endometrium, especially with higher estrogen doses.
Women who have had a total hysterectomy can usually use estrogen alone, although conditions such as significant endometriosis may require an individual approach. Low-dose vaginal estrogen generally doesn’t require progesterone either.
Progesterone, progestogen, progestin: what’s the difference?
Progestogen is the umbrella term. It covers natural progesterone and synthetic compounds with progesterone-like effects, often called progestins.
What is micronized progesterone?
Micronized progesterone is chemically identical to the progesterone your body makes, which is why it’s often called body-identical or bioidentical. It is usually taken as a capsule by mouth as part of combined HRT, often at bedtime. It suits many women who need endometrial protection while taking systemic estrogen, and may be a good option if you:
Prefer body-identical hormones
Have had unwanted effects from certain synthetic progestogens
It can be used in both sequential and continuous combined HRT.
Does progesterone help with sleep? Some women find that oral micronized progesterone improves their sleep, partly because it has a sedating effect. It should not be used as a general treatment for insomnia unrelated to menopause.
What are synthetic progestogens?
Synthetic progestogens are compounds designed to act on progesterone receptors. Several types are used in HRT, and their effects and side effects vary. They can be included in combined HRT tablets or patches, or delivered locally through a hormonal intrauterine device.
Can a hormonal IUD be used as part of HRT?
Yes. A 52 mg levonorgestrel intrauterine device (hormonal coil or IUD) can protect the endometrium while you use systemic estrogen, when used according to the product guidance. It can be especially useful if you:
still need contraception during perimenopause
have heavy or irregular bleeding
would rather not take progesterone by mouth
It often reduces menstrual bleeding, and periods may stop altogether. Not all hormonal IUDs are approved or adequately studied for endometrial protection during HRT. The specific device and its replacement interval must be checked.
What are the side effects of progesterone and progestogens?
Side effects depend on the type and formulation, and may include:
Breast tenderness
Bloating
Headaches
Mood changes
Irregular bleeding
Acne (mainly with some synthetic progestogens)
Drowsiness or dizziness (mainly with oral micronized progesterone, which is why it’s often taken at bedtime)
Many women tolerate one progestogen much better than another. Changing the type or how it’s taken can often help.
Sequential or continuous combined HRT: what’s the difference?
If you have a uterus, estrogen and a progestogen can be combined in two main ways.
Sequential (cyclical) HRT
You take estrogen every day and add a progestogen for part of each month. A predictable withdrawal bleed usually follows the progestogen phase. This is commonly used in perimenopause, or if your last period was fairly recent. It relieves symptoms while protecting the endometrium.
Continuous combined HRT
You take both estrogen and a progestogen every day. This is generally preferred after menopause, once periods have stopped. The aim is symptom relief and endometrial protection without monthly bleeding. Spotting or irregular bleeding is common in the first months and usually settles over time.
When should bleeding on HRT be checked? Bleeding that is persistent or heavy, or that starts after a period without any bleeding, should be assessed by a doctor.
This article is general information and not a substitute for medical advice. Talk to your doctor about which hormone therapy is right for you.
FAQ – Progesterone therapy for women in menopause
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If you have a uterus, progesterone protects the endometrium from the stimulating effect of systemic estrogen.
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Usually not. After a total hysterectomy, estrogen alone is usually enough, although conditions such as significant endometriosis may require an individual approach.
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Micronized progesterone is chemically identical to the progesterone the body produces, which is why it’s often described as body-identical or bioidentical.
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A 52 mg levonorgestrel IUD can provide endometrial protection during HRT, but not all hormonal IUDs are approved for this.
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Spotting is common in the first months of continuous combined HRT and usually settles. Persistent, heavy or new bleeding should be checked by a doctor.