Testosterone

Mechanism

Testosterone binds the intracellular androgen receptor, which then acts as a ligand-activated transcription factor at androgen response elements. In tissues expressing 5-alpha-reductase it is converted to dihydrotestosterone, a higher-affinity androgen receptor ligand responsible for much of the prostate and scalp/skin activity. In tissues expressing aromatase (CYP19A1), including adipose tissue, bone and brain, it is converted to estradiol and acts through the oestrogen receptors; several effects attributed to testosterone, including on bone and on some cardiometabolic markers, are mediated by this aromatised fraction. Exogenous administration also suppresses hypothalamic GnRH and pituitary LH/FSH by negative feedback, reducing endogenous testicular testosterone and spermatogenesis.

Reported effects

What sources associate with this compound. Reported categories, not outcomes we have graded — each would need its own citation and rung.

• In men aged 65 and over with serum testosterone below 275 ng/dL and symptoms of hypoandrogenism, transdermal testosterone was studied against placebo for one year and increased sexual activity, sexual desire and erectile function; the same trials measured 6-minute walk distance and fatigue and found no significant improvement (Snyder, NEJM 2016).
• In men with hypogonadism and pre-existing or high cardiovascular risk, testosterone replacement was studied as a safety endpoint against placebo and was non-inferior to placebo for major adverse cardiac events (TRAVERSE, NEJM 2023). This is a safety finding, not a benefit finding.
• In postmenopausal women diagnosed with hypoactive sexual desire disorder after biopsychosocial assessment, testosterone at doses approximating premenopausal physiological concentrations was studied in randomised trials and increased satisfying sexual events by an average of about one per month, with improvements in desire, arousal, orgasm, pleasure and sexual responsiveness (Islam, Lancet Diabetes Endocrinol 2019; Global Consensus Position Statement 2019).
• Cognition in women was measured and no support was found: the consensus statement records insufficient evidence to enhance cognitive performance or delay cognitive decline.
• Bone mineral density in women was measured and no effect on spine, hip or femoral neck was demonstrated at 12 months.
• Depressed mood and general wellbeing in women were measured and no effect of testosterone was shown.
• Lean mass, total fat and muscle strength in women were measured and no statistically significant effect was shown.

Half-life, storage & sport

Elimination half-life

approximately 8 days (human, intramuscular) — study. This figure is for testosterone CYPIONATE injected intramuscularly, and is the label figure. It does not apply to testosterone enanthate, undecanoate, propionate, transdermal or oral formulations, which differ by ester and route. No half-life for the other esters is on file here.

Storage

not on file — no stability record found.

In sport (WADA)

not recorded as a yes or no — Exogenous testosterone and its esters are named in class S1.1, Anabolic Androgenic Steroids administered exogenously, within S1 Anabolic Agents. Prohibited at all times, in-competition and out-of-competition. S1 substances are non-specified substances. the list WADA has clarified that the esters of prohibited anabolic agents are themselves prohibited, which covers testosterone cypionate, enanthate, undecanoate and propionate. Detection uses steroid-profile and isotope-ratio methods rather than a simple concentration threshold.

The half-life on file is 1.1 wk, measured intramuscularly. No dosing schedule could be read from this record, so the curve below is one dose drawn from the moment it is given. Nothing here says how often it is repeated.

The rise is not modelled and the axis is not a blood level. No absorption rate constant and no volume of distribution are on file, so each dose appears at full height the instant it is given, and the axis is percent of this compound's own peak.

Reported adverse effects

• Polycythaemia (raised haematocrit), listed on the FDA label for testosterone cypionate.

  reversibility not on file

• Venous thromboembolism, including deep vein thrombosis and pulmonary embolism, carried as a labelled warning.

  reversibility not on file

• Increased blood pressure, carried as a labelled warning, with associated major adverse cardiovascular event risk language.

  reversibility not on file

• Gynaecomastia, attributable in part to aromatisation to estradiol.

  reversibility not on file

• Hepatic adenoma and hepatocellular carcinoma with prolonged high-dose use, per the label.

  reversibility not on file

• Suppression of endogenous testosterone production and of spermatogenesis through negative feedback on LH and FSH.

  reversibility not on file

• In women, androgenic effects reported in trials include acne and hirsutism; the Islam 2019 meta-analysis reports these as the main excess adverse effects and reports no long-term safety data beyond about two years.

  reversibility not on file

Literature on file 8

• human observational
  Islam RM et al. Safety and efficacy of testosterone for women: a systematic review and meta-analysis of randomised controlled trial data. Lancet Diabetes Endocrinol 2019;7(10):754-766 graded on: a synthesis of human studies — “systematic review”
• human RCT
  Snyder PJ et al. Effects of Testosterone Treatment in Older Men. N Engl J Med 2016;374:611-624 graded on: names a randomised controlled trial — the indexed publication type — “Randomized Controlled”
• human RCT
  Lincoff AM et al. Cardiovascular Safety of Testosterone-Replacement Therapy (TRAVERSE). N Engl J Med 2023;389:107-117 graded on: names a randomised controlled trial — the indexed publication type — “Randomized Controlled”
• human observational
  TRAVERSE registration record (NCT03518034) graded on: a registered clinical study — “clinicaltrials.gov”
• human RCT
  FDA approval graded on: an FDA approval (), which requires adequate and well-controlled human investigations — “”

Not graded

3 citations whose study design could not be read from the title. Left ungraded rather than guessed at.

• not graded
  Global Consensus Position Statement on the Use of Testosterone Therapy for Women (J Clin Endocrinol Metab 2019;104:4660-4666)
• not graded
  Testosterone Cypionate Injection, USP CIII - FDA prescribing information (DailyMed)
• not graded
  WADA Prohibited List - S1 Anabolic Agents

Identity

Also called

• testosterone cypionate
• testosterone enanthate
• testosterone undecanoate
• TRT
• test cyp

Listed prices 37

What 7 shops we track listed for Testosterone, read from their own public catalogues on 2026-09-14. We take no commission on these and they are not ranked by any payment — how vendors are scored.