Testosterone
Overview
Testosterone measures the primary male sex hormone produced mainly by testicular Leydig cells in men and ovarian theca cells in women, circulating as free hormone or bound to SHBG and albumin. It regulates masculinization, spermatogenesis, muscle mass, bone density, libido, and erythropoiesis through androgen receptor activation. Low levels indicate hypogonadism, aging, chronic illness, or obesity, while high levels suggest anabolic steroid use, tumors, or PCOS in women; it is clinically useful for diagnosing hypogonadism, guiding testosterone replacement therapy, and evaluating disorders of sexual development and hyperandrogenism.
Clinical Use Cases
- Diagnosing primary or secondary hypogonadism in men.
- Evaluating delayed puberty in adolescent males.
- Assessing hyperandrogenism in women (PCOS, congenital adrenal hyperplasia).
- Monitoring testosterone replacement therapy efficacy and safety.
- Investigating infertility associated with hormonal imbalance.
Specimen Types
- Serum (preferred).
- Plasma (EDTA).
- Saliva (free testosterone).
Measurement Methods
- Immunoassays (chemiluminescent, high-sensitivity).
- Liquid chromatography-tandem mass spectrometry (LC-MS/MS, gold standard).
- Equilibrium dialysis (free testosterone).
Test Preparation and Influencing Factors
- Morning collection (7-10 AM) due to diurnal rhythm.
- Fasting not required.
- Avoid biotin supplements, anabolic steroids, or recent testosterone use.
- Obesity, diabetes, opioids, and glucocorticoids lower levels.
- SHBG abnormalities require free testosterone measurement.
Synonyms
- Total testosterone.
- Serum T.