Testosterone replacement therapy glossary

Short, plain-English definitions of the terms you'll meet when choosing a Testosterone Replacement Therapy provider in Florida.

What is a selective estrogen receptor modulator (SERM)?: A selective estrogen receptor modulator (SERM) is a pharmaceutical compound that blocks estrogen's feedback signals to the brain, allowing the body to produce more of its own testosterone without external hormone injections.
What is a subcutaneous injection?: A subcutaneous injection is an administration method that delivers testosterone into the fat layer directly under the skin, rather than into muscle tissue.
What is an aromatase inhibitor (AI)?: An aromatase inhibitor is a medication such as anastrozole that blocks the enzyme aromatase, which converts testosterone to estradiol, and is sometimes prescribed alongside TRT to manage estrogen levels.
What is an intramuscular injection?: An intramuscular injection (IM) is an injection administered deep into muscle tissue, commonly used in testosterone replacement therapy to deliver testosterone esters with extended absorption and consistent blood levels.
What is aromatase?: Aromatase is an enzyme found throughout the body that catalyzes the conversion of testosterone to estradiol, a form of estrogen, and is relevant to TRT patients because excessive aromatization can lead to elevated estrogen levels.
What is bioavailable testosterone?: Bioavailable testosterone is the portion of testosterone that exists in free form or loosely bound to albumin, making it biologically active and available for tissue uptake.
What is estradiol (E2) in men?: Estradiol (E2) is the active estrogen form produced when testosterone converts via the enzyme aromatase, and is monitored in men on TRT to maintain hormonal balance and manage side effects.
What is follicle stimulating hormone (FSH)?: Follicle stimulating hormone (FSH) is a pituitary gland hormone that directly controls sperm production in the testes and is routinely measured in TRT baseline screening.
What is free testosterone?: Free testosterone is the small fraction of testosterone circulating unbound in the blood, which is biologically active and available to tissues, as opposed to testosterone bound to carrier proteins.
What is hematocrit?: Hematocrit is the percentage of red blood cells by volume in your blood, measured through a standard blood test and routinely checked during testosterone replacement therapy.
What is human chorionic gonadotropin (hCG)?: Human chorionic gonadotropin (hCG) is a hormone-mimicking medication administered during testosterone replacement therapy to maintain testicular size and sperm production by simulating the action of luteinizing hormone.
What is hypogonadism?: Hypogonadism is a medical condition in which the body produces insufficient testosterone, stemming from either testicular dysfunction (primary) or hormonal signaling problems from the pituitary or hypothalamus (secondary).
What is luteinizing hormone (LH)?: Luteinizing hormone (LH) is a pituitary hormone that signals the testes to produce testosterone, making it a key marker evaluated during testosterone replacement therapy screening.
What is polycythemia?: Polycythemia is an abnormal increase in red blood cell count that can develop as a side effect of testosterone replacement therapy and necessitates regular blood work monitoring.
What is primary hypogonadism?: Primary hypogonadism is a condition where the testicles fail to produce adequate testosterone despite the pituitary gland sending normal hormonal signals to stimulate production.
What is prostate specific antigen (PSA)?: Prostate specific antigen (PSA) is a protein produced by the prostate gland that appears in the bloodstream at elevated levels when the gland is enlarged, inflamed, or cancerous.
What is secondary hypogonadism?: Secondary hypogonadism is a condition of low testosterone resulting from dysfunction in the pituitary gland or hypothalamus rather than from testicular failure itself.
What is sex hormone binding globulin (SHBG)?: Sex hormone binding globulin (SHBG) is a protein produced by the liver that binds to testosterone and other sex hormones in the bloodstream, reducing the amount of free testosterone available to body tissues.
What is testosterone cypionate?: Testosterone cypionate is a synthetic testosterone ester suspended in oil for intramuscular injection, designed for prolonged release into the bloodstream and widely used in testosterone replacement therapy.
What is testosterone enanthate?: Testosterone enanthate is a synthetic testosterone compound attached to an enanthate ester, administered as an injection to raise testosterone levels in testosterone replacement therapy.
What is testosterone pellet therapy?: Testosterone pellet therapy involves subcutaneous implantation of small pellets that release testosterone gradually over 3-6 months, providing steady hormone levels without frequent dosing.
What is testosterone undecanoate?: Testosterone undecanoate is a long-acting ester of testosterone available in oral or injectable formulations that requires less frequent dosing than shorter-acting testosterone products.
What is total testosterone?: Total testosterone is the blood test measurement that includes all testosterone in the bloodstream, both the hormone bound to proteins and the unbound portion, used to assess overall hormone levels.
What is transdermal testosterone gel?: Transdermal testosterone gel is a prescription topical medication applied daily to the skin that delivers testosterone directly into the bloodstream through absorption.