Hormone replacement therapy (HRT) is a treatment that supplements hormones your body has stopped making in sufficient quantities. Most commonly, it refers to estrogen and progesterone therapy used to manage menopause symptoms, though the term also applies to gender-affirming hormone therapy for transgender individuals. The core idea is the same in both cases: bring hormone levels to a range that alleviates symptoms and supports long-term health.
How HRT Works for Menopause
As you approach menopause, your ovaries gradually stop producing estrogen and progesterone. That drop triggers a cascade of symptoms: hot flashes, night sweats, vaginal dryness, painful sex, mood swings, insomnia, and even urinary leakage. HRT replaces those missing hormones, and once levels rise, most people find relief.
The specific hormones you receive depend on whether you still have a uterus. If you do, you’ll take both estrogen and a progestogen (a form of progesterone). Estrogen alone would cause the uterine lining to grow unchecked, raising the risk of abnormal cell changes or cancer. Progesterone prevents that by keeping the lining from proliferating. If you’ve had a hysterectomy, estrogen alone is typically sufficient.
In some cases, testosterone can be added to menopausal HRT for women experiencing persistent low sexual desire after other causes have been ruled out and standard HRT has been tried first.
Forms of HRT
HRT comes in two broad categories: systemic and local. Systemic options, including pills, skin patches, gels, and sprays, circulate hormones throughout your body and address the full range of menopause symptoms. Local options, like vaginal creams, rings, or dissolvable tablets, deliver estrogen directly to vaginal tissue and are best suited when dryness or discomfort during sex is your primary concern.
The distinction between oral and transdermal (skin-delivered) estrogen matters more than many people realize. Oral estrogen passes through the liver before reaching the rest of your body, which raises the risk of blood clots. A systematic review comparing the two routes found that oral estrogen users had roughly 3.5 times the blood clot risk of non-users, while transdermal estrogen users showed no significant increase at all. For women who already carry a higher clotting risk, such as those with a genetic clotting tendency, oral HRT raised that risk 25-fold compared to non-users, while transdermal estrogen raised it only fourfold. Transdermal delivery also tends to lower triglycerides rather than raising them, which is the opposite of what oral estrogen does.
Benefits Beyond Symptom Relief
The most well-documented benefit of HRT outside of symptom control is bone protection. After menopause, the loss of estrogen accelerates bone breakdown. HRT slows that process by reducing bone turnover by roughly 30%, which translates to a 24 to 39% reduction in osteoporotic fractures based on data from the Women’s Health Initiative, the largest randomized trial on the subject. That’s a meaningful drop in hip, spine, and wrist fractures.
Many women also report improvements in mood, sleep quality, and overall sense of well-being, effects that are harder to quantify in trials but consistently reported.
The Timing Window
One of the most important findings in HRT research over the past two decades is the “window of opportunity” concept. Starting HRT before age 60, or within 10 years of menopause onset, is associated with significant reductions in heart disease and overall mortality. Women who begin HRT well after that window don’t see the same cardiovascular benefit and may face increased risk. This timing effect helps explain why earlier studies that enrolled older women produced alarming results, while data from women who started treatment closer to menopause tell a much more favorable story. The current consensus supports initiating HRT during this window and continuing for six or more years for the greatest benefit in quality-adjusted life years.
Breast Cancer and Other Risks
Breast cancer risk is the concern that dominates most conversations about HRT, and the answer depends heavily on which type you use. Estrogen-only HRT (for women without a uterus) actually lowered breast cancer incidence by 14% compared to never using hormones, according to recent analysis. Combined estrogen-plus-progesterone HRT, however, raised breast cancer rates by about 10%, with an 18% increase in women who used it for more than two years. In practical terms, the cumulative risk of breast cancer before age 55 was about 4.5% for combined HRT users, compared to 4.1% for non-users and 3.6% for estrogen-only users. Those are real but relatively small differences in absolute risk.
Blood clots remain a concern, particularly with oral estrogen, as noted above. Switching to a patch, gel, or spray largely addresses that risk. Side effects like breast tenderness, bloating, or spotting are common early on but typically resolve within a few months.
Bioidentical vs. Conventional Hormones
Bioidentical hormones are chemically identical to the hormones your body produces. Some bioidentical formulations are commercially manufactured, FDA-approved, and held to strict quality standards. Others are custom-compounded at specialty pharmacies based on saliva testing, and this is where things get less reliable. Compounded formulations aren’t subject to the same quality controls, so the dose and purity can vary from batch to batch. The saliva tests used to guide compounding don’t reliably reflect blood hormone levels or correlate with symptoms. Research has not shown that compounded bioidentical hormones offer advantages over standard commercially made versions.
Gender-Affirming Hormone Therapy
HRT also refers to hormone therapy used by transgender individuals to align their physical characteristics with their gender identity. The hormones and goals differ depending on the direction of transition.
Feminizing Hormone Therapy
Transgender women typically receive estrogen (as pills, injections, or patches) along with an anti-androgen to suppress testosterone. The anti-androgen component can take several forms, including medications that block testosterone’s effects or suppress its production. The goal is to bring testosterone below 50 ng/dL while maintaining estrogen levels in the range typical for cisgender women (100 to 200 pg/mL). Physical changes include breast development, softer skin, redistribution of body fat, and reduced body hair growth. These changes develop gradually over months to years.
Masculinizing Hormone Therapy
Transgender men receive testosterone, delivered through injections, skin gels, patches, or implanted pellets. The target is testosterone levels within the normal range for cisgender men. Physical changes include voice deepening, facial hair growth, increased muscle mass, fat redistribution, and cessation of menstrual periods. As with feminizing therapy, these effects unfold over months, with some changes (like voice deepening) becoming permanent.
Both types of gender-affirming HRT require regular blood work. Hormone levels are typically checked every three months during the first year to ensure they’re in the target range and to catch any issues early. For those taking certain anti-androgens, kidney function and electrolyte levels (especially potassium) are also monitored. After levels stabilize, testing becomes less frequent but continues long-term.