Hormonal therapy is a medical treatment that adds, blocks, or replaces hormones in the body to treat a specific condition. It spans several areas of medicine: relieving menopause symptoms, treating hormone-sensitive cancers, replacing hormones the body can no longer produce on its own, and supporting gender transition. The approach differs depending on the goal, but the core idea is the same. Hormones are chemical messengers that control processes throughout your body, and hormonal therapy adjusts those signals when something is out of balance or when a disease depends on them.
Hormone Therapy for Menopause
The most common reason people encounter hormonal therapy is menopause. As estrogen levels drop, many women experience hot flashes, night sweats, vaginal dryness, sleep disruption, and mood changes. Hormone therapy replaces the estrogen (and sometimes progesterone) the ovaries no longer produce in sufficient amounts, and it remains the most effective treatment for these symptoms.
If you still have your uterus, you’ll typically receive a combination of estrogen and a progestin. That’s because estrogen alone raises the risk of endometrial cancer, the cancer of the uterine lining. Adding a progestin counteracts that risk. Women who have had a hysterectomy can safely take estrogen on its own.
A large 2024 study found that estrogen-only therapy used beyond age 65 was associated with a 19% reduction in mortality, a 16% reduction in breast cancer risk, and an 11% reduction in heart attack risk compared with never using it or stopping at 65. Combination therapy told a more nuanced story: estrogen plus a synthetic progestin increased breast cancer risk by 10% to 19%, but also cut endometrial cancer risk by 45% and ovarian cancer risk by 21%. The breast cancer risk dropped when lower doses or non-oral forms were used, like patches or vaginal preparations.
Common side effects of menopausal hormone therapy include headaches, breast tenderness, bloating, nausea, mood changes, and fluid retention in the hands or feet. Most of these are mild and often improve within the first few months of treatment.
How It’s Used in Cancer Treatment
Some cancers need hormones to grow. Breast cancer and prostate cancer are the two most prominent examples. In these cases, hormonal therapy works in the opposite direction from menopause treatment: instead of adding hormones, the goal is to starve the tumor of the hormones fueling it.
There are two broad strategies. The first blocks the body’s ability to produce the hormone entirely. For breast cancer, this might involve medications that shut down estrogen production by inhibiting an enzyme called aromatase. For prostate cancer, treatments can suppress testosterone production. The second strategy interferes with how hormones behave once they’re made, blocking them from attaching to receptors on cancer cells. When estrogen can’t dock onto a breast cancer cell’s receptor, the cell loses its growth signal.
In estrogen receptor-positive breast cancer, which accounts for the majority of breast cancer cases, hormonal therapy is one of the most effective treatments available. It’s often used after surgery to reduce the chance of recurrence, and it can also slow or stop advanced disease. Because these treatments lower hormone levels or block hormone activity throughout the body, side effects can mirror menopause symptoms: hot flashes, joint pain, fatigue, and changes in bone density over time.
Gender-Affirming Hormone Therapy
For transgender individuals, hormone therapy aligns the body’s physical characteristics with their gender identity. Transgender men typically take testosterone to promote masculinizing changes, while transgender women take estrogen (often alongside an anti-androgen medication that suppresses testosterone’s effects) to promote feminizing changes.
Masculinizing Therapy
Testosterone therapy produces a predictable sequence of changes. Within the first one to six months, skin becomes oilier, acne may develop, and menstrual periods typically stop. Facial and body hair begin appearing around three to six months, though a full beard can take three to five years. Voice deepening starts between three and twelve months and usually reaches its full depth within one to two years. Muscle mass increases over six to twelve months, with maximum effect taking two to five years. Fat redistribution, shifting from hips and thighs toward the midsection, begins within the first few months. Many of these changes, particularly voice deepening and hair growth, are permanent even if testosterone is later discontinued.
Feminizing Therapy
Estrogen therapy follows its own timeline. Breast growth begins around three to six months and continues developing for two to three years. Body fat shifts toward the hips and thighs over a similar period. Skin becomes softer and less oily within three to six months. Body and facial hair gradually thins and slows, though this process takes over a year to begin and more than three years to reach its full effect. Testicular volume decreases, and sex drive and spontaneous erections typically decline within the first few months. Male pattern hair loss stops within one to three months, though hair that has already been lost generally does not regrow.
Replacing Hormones the Body Can’t Make
Beyond menopause and gender-affirming care, hormone therapy is essential for people whose glands simply don’t produce enough of a critical hormone. This category covers a range of conditions. People with an underactive thyroid take thyroid hormone daily. Those with adrenal insufficiency, where the adrenal glands fail to produce adequate cortisol, take a low-dose replacement to maintain normal energy, blood pressure, and stress response. Growth hormone deficiency, often caused by damage to the pituitary gland, can be treated with growth hormone injections after proper testing confirms the deficiency.
Younger women whose ovaries stop functioning early, a condition called premature ovarian insufficiency, also receive hormone replacement to protect bone density, heart health, and overall well-being until the typical age of menopause. In all of these cases, the principle is straightforward: the body needs a hormone it can’t produce, so the treatment supplies it.
How Hormonal Therapy Is Delivered
One of the practical decisions you’ll make with your provider is how to take the hormones. Options include oral pills, skin patches, topical gels or creams, injections, nasal sprays, subdermal pellets implanted under the skin, and vaginal rings. The choice depends on the condition being treated, convenience, and how your body processes the medication.
Route of delivery matters beyond convenience. For menopausal hormone therapy, transdermal options like patches and gels bypass the liver and appear to carry a lower risk of blood clots compared to oral pills. For testosterone therapy in gender-affirming care, gels and creams are applied to clean, dry skin on the lower abdomen or upper thighs to maintain steady hormone levels. Injections, given every one to two weeks, produce more of a peak-and-trough pattern that some people notice in their energy and mood.
Risks and Side Effects Across Uses
Every form of hormonal therapy carries trade-offs, and the specific risks depend heavily on which hormones you’re taking, how they’re delivered, and how long you use them. For menopausal therapy, the primary concerns are blood clots, cardiovascular effects, and breast cancer risk with long-term combination use. As noted earlier, these risks vary significantly by formulation and route: transdermal estrogen and lower doses appear substantially safer on most measures than oral combined therapy.
For cancer-related hormone therapy, side effects stem from hormone deprivation. Blocking estrogen can accelerate bone loss and raise fracture risk. Suppressing testosterone in prostate cancer treatment can lead to fatigue, weight gain, reduced muscle mass, and changes in mood. These effects are managed with monitoring and supportive treatments like bone-protective medications or exercise programs.
Gender-affirming hormone therapy carries its own profile. Testosterone therapy may increase red blood cell counts, which requires periodic blood monitoring, and can raise cholesterol levels. Estrogen therapy, particularly at higher doses or when taken orally, increases the risk of blood clots. Smoking significantly compounds this risk. For both masculinizing and feminizing therapy, fertility is affected, and people who may want biological children in the future are encouraged to discuss preservation options before starting treatment.