Estrogen and progesterone are hormones that help regulate the menstrual cycle, fertility, and overall health. During perimenopause, levels of estrogen and progesterone rise and fall, leading to changes in your menstrual cycle, mood, and more. This typically happens in your 40s but can occur earlier or later, as well as with medically induced menopause.

What Is Estrogen?

As one of the primary sex hormones, estrogen helps regulate puberty, menstruation, fertility, and menopause. The ovaries produce estrogen, which travels through the bloodstream to tissues throughout the body.

Estrogen levels naturally rise and fall during different life stages:

• Puberty — Estrogen levels begin to increase, leading to breast development and other secondary sex characteristics.
• Menstrual cycle — Your body needs enough estrogen to maintain a regular menstrual cycle.
• Fertility — Estrogen is needed for ovulation (when the body releases a mature egg in preparation for pregnancy).
• Menopause — A drop in estrogen levels triggers perimenopause and menopause-related changes.

Estrogen also plays a role in sexual health. It affects libido (sex drive), so lower levels can lead to a lower sex drive. Estrogen also supports overall health in males and females and is essential for:

• Heart health
• Brain function
• Bone density
• Muscle mass
• Blood sugar levels
• Cholesterol levels

What Is Progesterone?

Progesterone is a sex hormone that works with estrogen to maintain reproductive health. Progesterone helps regulate the menstrual cycle and early phases of pregnancy and supports:

• Conception — Progesterone helps the endometrium (lining of the uterus) thicken and prepare for a fertilized egg. After ovulation, progesterone prepares the uterus for possible pregnancy.
• Menstruation — If pregnancy doesn’t occur after ovulation, progesterone levels drop, causing the uterine lining to shed and leading to a menstrual period.
• Pregnancy — When a fertilized egg implants into the uterine lining, progesterone levels rise until the third trimester to support the developing embryo.
• Lactation — Progesterone helps prepare the breasts for milk production during pregnancy.

One of progesterone’s main functions is to support a healthy pregnancy. This hormone maintains a thickened uterine lining so a fertilized egg can grow and receive nutrients.

During pregnancy, progesterone production increases to prevent ovulation and uterine contractions. This reduces the risk of preterm (early) labor and miscarriage.

Low progesterone levels may make it harder to get pregnant. A blood test can check progesterone levels during an infertility evaluation.

What Happens to Hormone Levels During Perimenopause?

During perimenopause, the ovaries may produce estrogen and progesterone irregularly. A dip in estrogen is linked to many common perimenopause symptoms and changes, including:

• Irregular periods — Changes in your menstrual cycle are often the first sign of perimenopause, as declining estrogen levels make periods irregular and unpredictable. Periods may be heavier, lighter, more uncomfortable, or skipped.
• Mood changes — Increased irritability, mood swings, depression, and anxiety can occur during perimenopause.
• Hot flashes — These sudden feelings of warmth and flushing may seem to come out of nowhere and can happen at any time, day or night.
• Sleep problems — Trouble falling or staying asleep is common. Hot flashes and night sweats may also interfere with rest.
• Vaginal changes — Lower estrogen levels cause vaginal tissue to become thinner, leading to dryness, irritation, and pain during sexual intercourse.
• Bladder issues — Thinner vaginal and urinary tissues may raise your risk of urinary infections and cause leakage. It’s also common to feel an intense or frequent urge to urinate.
• Lower libido — Sexual desire often decreases during and after perimenopause. This may be linked to hormone changes and vaginal dryness.

Perimenopause and menopause can also cause hidden symptoms or changes that aren’t immediately noticeable. Shifting hormone levels may lead to:

• Reduced fertility — Ovulation happens less often, making pregnancy less likely. When the ovaries produce less estrogen and progesterone, conception becomes more difficult.
• Bone density loss — Estrogen helps maintain healthy bones, so lower levels raise the risk of weak bones and osteoporosis.
• Changes in cholesterol levels — Lower estrogen levels may increase low-density lipoprotein (LDL) cholesterol and decrease high-density lipoprotein (HDL) cholesterol, raising the risk of heart disease.

What Is Testosterone?

The sex hormone testosterone is classified as an androgen — it supports the development of traits such as facial hair and increased muscle mass. Testosterone levels are typically much higher in males.

The ovaries produce small amounts of testosterone, which contributes to sex drive and supports muscle mass and bone density. Much of this testosterone is converted to estradiol, a form of estrogen. During perimenopause, testosterone levels gradually decrease, often beginning in the 40s.

What Is Hormone Therapy?

Hormone therapy, also known as hormone replacement therapy, is a common treatment for perimenopause and menopause. Menopause hormone therapy works by replacing some of the hormones that decline during this transition.

Your healthcare provider may recommend taking a low dose of estrogen or a combination of estrogen and progesterone to relieve symptoms such as hot flashes and night sweats. Hormone therapy can also maintain bone density and lower your risk of osteoporosis.

The two main types of hormone therapy are systemic (whole-body) hormone therapy and low-dose vaginal estrogen. Whole-body therapy includes estrogen taken as a pill, skin patch, gel, cream, spray, or ring. Your entire body absorbs the medication.

Low-dose vaginal estrogen works primarily in the vaginal tissue and is used mainly for vaginal or urinary symptoms.

If you’re experiencing bothersome symptoms related to perimenopause or menopause, consider talking with your healthcare provider about hormone therapy. Although this treatment has significant benefits, it also carries risks. Your provider can help you weigh the pros and cons and determine the best approach for managing your symptoms.