menopausal hormone therapy

menopausal hormone therapy (MHT), treatment used to relieve symptoms associated with menopause, the life stage marked by the natural decline of ovarian hormone production. As levels of estrogen and progesterone fall, many individuals experience vasomotor symptoms (such as hot flashes and night sweats), sleep disturbance, mood changes, and genitourinary symptoms. Menopausal hormone therapy (MHT), sometimes referred to simply as hormone therapy, is given to restore concentrations of these hormones to physiologically active levels.

Uses

MHT is indicated primarily for the treatment of moderate to severe vasomotor symptoms, which can significantly impair quality of life. It is also effective in managing genitourinary syndrome of menopause (GSM), a condition characterized by vaginal dryness, irritation, urinary urgency, and discomfort during sexual intercourse. In addition, hormone therapy may help prevent osteoporosis (bone loss) and reduce the risk of osteoporotic fractures in individuals at elevated risk. In some cases, MHT may be considered for premature menopause or primary ovarian insufficiency, where early hormone loss carries increased risks for bone and cardiovascular complications. Its use solely for chronic disease prevention, however, is generally not recommended.

Types and mechanisms of action

Estrogen therapy, which is typically combined with supplemental calcium, is effective in decreasing bone loss when begun during menopause, although it will provide some benefit if started later. This therapy is used only in people who have undergone hysterectomy and therefore no longer have a uterus. In people who have an intact uterus, the administration of estrogen alone stimulates continuous proliferation of the endometrial lining. Without progesterone to trigger monthly shedding of the lining, estrogen-only therapy may lead to endometrial cancer. For this reason, postmenopausal people with an intact uterus who use hormone therapy are prescribed a combination of estrogen and a progesterone-type hormone. Most combination hormone therapies include a synthetic form of progesterone known as a progestin, which helps protect the uterine lining while allowing patients to benefit from symptom relief.

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The various hormones used in MHT work by restoring circulating estrogen levels, which has impacts on different body systems. During menopause, as estrogen levels fall, the hypothalamus—the brain region that functions as the body’s thermostat—becomes unusually reactive to even slight shifts in internal or external temperature cues. When estrogen is restored, the thermoregulatory centers in the hypothalamus are stabilized, helping alleviate hot flashes and night sweats. Estrogen also maintains the integrity of vaginal and urinary tissues, improves blood flow to mucosal surfaces, and helps preserve bone density by reducing bone resorption.

Administration and side effects

MHT can be delivered by various routes, including oral tablets, transdermal patches, topical gels or sprays, vaginal creams, and vaginal rings. The choice of route depends on symptom profile, patient preference, medical history, and risk factors. Transdermal delivery may be preferred in individuals at higher risk for thromboembolic events, as it avoids first-pass metabolism in the liver (substantial degradation or inactivation of a drug before it reaches systemic circulation). Clinicians individualize treatment plans accordingly, typically recommending the lowest effective dose for the shortest duration necessary to manage symptoms.

MHT is associated with various side effects, including breast tenderness, bloating, headache, and irregular bleeding, particularly during the first months of therapy. More-serious risks depend on formulation, duration of use, and patient characteristics. Both combined and estrogen-only systemic therapies may increase the risk of venous thromboembolism, in which a blood clot breaks free from its point of formation and becomes lodged in a blood vessel. In certain populations, they may also increase the risk of stroke—brain injury incurred by a lack of blood flow to the brain (often triggered by a thromboembolism). Age and timing appear to influence risk. Evidence suggests that starting MHT near the onset of menopause in healthy individuals under age 60 carries a more favorable benefit-risk profile than starting therapy later in life.