Estrogens

Estrogens are a group of sex hormones that play an important role in women’s health. They help control the menstrual cycle, support the reproductive system, and affect many other organs in the body. Estrogens are also present in men in smaller amounts.

Estrogen production mainly happens in the ovaries. Smaller amounts are made in the adrenal glands and in adipose tissue (body fat). During pregnancy, the placenta also produces estrogen. Estrogen levels rise and fall throughout life. They change during the menstrual cycle, pregnancy, perimenopause, and menopause.

Low estrogen levels are common in postmenopausal women and can lead to symptoms like hot flashes, vaginal dryness, and bone loss that may cause osteoporosis. High levels can also cause problems, including an increased risk of certain conditions. Estrogen medicines are used to treat menopause symptoms, prevent bone loss, and for other medical reasons.

Estrogens are natural hormones made by the body. They belong to a group of hormones called sex hormones. The three main natural types are:

• Estradiol: The main and most powerful form of estrogen during the reproductive years.
• Estrone: The main type found after menopause.
• Estriol: A weaker form of estrogen, mainly made during pregnancy.

Estradiol is the most common form of estrogen used in medicines. These hormones are a key part of endocrinology, the study of how hormones control body functions.

Estrogens help regulate menstruation, ovulation, and the growth of the uterine lining. They work closely with other hormones like progesterone, FSH (follicle-stimulating hormone), and androgens to keep hormone levels balanced. FSH helps a follicle in the ovary mature and release an egg during ovulation.

Estrogens travel through the bloodstream and attach to special proteins in cells called estrogen receptors. These receptors are found in many parts of the body, including the uterus, breasts, bones, heart, liver, and brain.

When estrogen binds to an estrogen receptor, it sends signals that change how cells grow and function. This affects the menstrual cycle, bone strength, mood, skin health, and even cholesterol and lipids in the blood.

Estrogen also helps maintain healthy cholesterol levels by increasing “good” HDL cholesterol and lowering “bad” LDL cholesterol. Because of this, it has effects on cardiovascular disease and heart disease risk, especially in younger women.

As women age and estrogen production drops, hormone levels change. These shifts can lead to menopause symptoms such as hot flashes, night sweats, mood changes, sleep problems, and vaginal dryness.

There are different forms of estrogen used in prescription medicines. They may be taken as pills, patches, gels, sprays, creams, or vaginal tablets.

Common types include:

• Estradiol (oral tablets, transdermal patches, gels, vaginal rings, and creams)
• Conjugated estrogens (tablets and vaginal creams)
• Esterified estrogens (oral tablets)
• Estrone (less commonly used as a medication)
• Estriol (used in some vaginal products outside the U.S.)

Some brand examples include:

• Estrace (estradiol)
• Premarin (conjugated estrogens)
• Vivelle-Dot (estradiol patch)
• Climara (estradiol patch)
• Estring (estradiol vaginal ring)

Estrogens may be used alone (estrogen alone) or combined with a progestin, a synthetic form of progesterone. In women who still have a uterus, estrogen replacement is usually combined with a progestin to reduce the risk of endometrial cancer.

Estrogens are also found in some birth control pills and other contraceptives, where they are combined with progestin to prevent ovulation.

Estrogen medicines have several important uses:

• Menopause and HRT: Estrogens are commonly used in hormone replacement therapy (HRT) to treat menopause symptoms such as hot flashes, vaginal dryness, and night sweats. HRT can improve the quality of life in postmenopausal women with moderate to severe symptoms.
• Prevention of osteoporosis: Low estrogen levels after menopause can weaken bones. Estrogen helps maintain bone density and may be used to help prevent osteoporosis in certain women at high risk.
• Genitourinary symptoms: Vaginal estrogen products can treat vaginal dryness, irritation, and painful intercourse caused by low estrogen levels.
• Birth control: Estrogen is part of many contraceptives. In these medicines, it works with progestin to prevent ovulation and change the uterine lining, reducing the chance of pregnancy.
• Other uses: In some cases, estrogens may be used in people with certain hormone imbalances, delayed puberty, or as part of gender-affirming care. They have also been used in some advanced prostate cancer treatments.

Common side effects include:

• Breast tenderness
• Nausea
• Headache
• Bloating
• Leg cramps
• Changes in menstrual cycle or spotting

Rare but serious side effects include:

• Blood clots in the legs or lungs
• Stroke
• Heart disease
• Breast cancer
• Endometrial cancer (when estrogen is used without progestin in women with a uterus)

The risk of blood clots and cardiovascular disease may be higher in women who smoke, have obesity, or have other risk factors. High levels of estrogen over time may also raise the risk of certain cancer cells growing, especially in the breast and uterus.

These are not all of the possible side effects of estrogens. You should always seek medical advice from your healthcare provider for any questions or concerns about your medical condition or treatment. Read all patient information, medication guides, or drug information sheets that come with this medication. You can also report adverse effects to the Food and Drug Administration at www.fda.gov/medwatch or 1-800-FDA-1088.

Although these medications are generally well-tolerated and safe, there are certain warnings, precautions, and drug interactions you should be aware of.

Warnings

Before starting Estrogens, it is crucial to discuss any existing health conditions with your healthcare provider. You should be sure that your healthcare provider is aware of all your medical conditions, including if you have:

• Increased risk of blood clots, especially in women who smoke, have obesity, or have a history of clotting problems
• Increased risk of stroke
• Possible increased risk of breast cancer with long-term use
• Increased risk of endometrial cancer when estrogen alone is used in women who still have a uterus
• Possible increased risk of gallbladder disease

Contraindications

• A history of breast cancer or suspected breast cancer
• Known or suspected endometrial cancer
• Unexplained vaginal bleeding
• Active or past blood clots
• History of stroke or heart attack
• Severe liver disease
• Known allergy to estrogen products

Women with a history of fibroids, endometriosis, or certain other conditions should discuss risks carefully with their healthcare provider.

Drug interactions

When Estrogens are taken with other prescription drugs, over-the-counter medications, vitamins, and supplements, it may change how they work or increase the frequency or severity of side effects. Make sure that you tell your healthcare professional about anything that you are taking to avoid any negative drug interactions, including:

• Certain seizure medicines
• Some antibiotics
• Antifungal drugs
• Herbal supplements like St. John’s wort