Hormone replacement therapy (HRT) is any form of hormone therapy wherein the patient, in the course of medical treatment, receives hormones, either to supplement a lack of naturally occurring hormones, or to substitute other hormones for naturally occurring hormones. Common forms of hormone replacement therapy include:

• Hormone replacement therapy for menopause is based on the idea that the treatment may prevent discomfort caused by diminished circulating estrogen and progesterone hormones, or in the case of the surgically or prematurely menopausal, that it may prolong life and may reduce incidence of dementia. It involves the use of one or more of a group of medications designed to artificially boost hormone levels. The main types of hormones involved are estrogens, progesterone or progestins, and sometimes testosterone. It is often referred to as "treatment" rather than therapy.
• Hormone replacement therapy for transgender people introduces hormones associated with the gender that the patient identifies with (notably testosterone for trans men and estrogen for trans women). Some intersex people may also receive HRT. Cross-sex hormone treatment for transgender individuals is divided into two main types: hormone replacement therapy (female-to-male) and hormone replacement therapy (male-to-female).
• Androgen replacement therapy (andropausal and ergogenic use) is a hormone treatment often prescribed to counter the effects of male hypogonadism. It is also prescribed to lessen the effects or delay the onset of normal male aging. Additionally, androgen replacement therapy is used for men who have lost their testicular function to disease, cancer, or other causes.