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Testosterone Replacement Therapy

Testosterone replacement therapy (TRT) is the standard treatment for symptomatic men with confirmed testosterone deficiency (TD). FDA-approved indications are limited to primary hypogonadism (testicular failure) and hypogonadotropic hypogonadism from established hypothalamic-pituitary disease.[1][2] The safety landscape has been fundamentally reshaped by the TRAVERSE trial (2023, NEJM, n = 5,246) establishing cardiovascular non-inferiority, and by the 2025 NEJM review that reframes the benefit–risk conversation around consistent benefit for libido, body composition, bone density, and anemia alongside a narrower list of genuine concerns — erythrocytosis, pulmonary embolism, atrial fibrillation, and (unexpectedly) clinical fractures.[2][3]

For related classes, see PDE5 inhibitors, Intracavernosal injection agents, and Androgen adjuncts.


Diagnosis — confirm the biochemical defect before prescribing

Both the AUA and Endocrine Society define testosterone deficiency as total testosterone (TT) <300 ng/dL (AUA) or <264 ng/dL (Endocrine Society) on two separate morning fasting measurements, combined with compatible clinical symptoms.[1][4]

Core diagnostic workup

TestPurpose
Total testosterone (fasting, morning, same lab / method)Initial screen[4]
Free testosterone (equilibrium dialysis or calculated)Confirmatory when TT is borderline or when SHBG-altering conditions are present (obesity, aging, liver disease, thyroid disorders)[1]
LH and FSHPrimary (elevated) vs secondary (low / normal) hypogonadism[5]
ProlactinIf LH is low or low-normal — evaluate for pituitary adenoma[5]
Secondary-cause workupPituitary MRI (hyperprolactinemia, panhypopituitarism), iron studies (hemochromatosis), karyotype (Klinefelter)[6]

When to measure testosterone even without classic sexual symptoms[4]

Unexplained anemia, low bone density, type 2 diabetes, chemotherapy or radiation exposure, HIV/AIDS, chronic opioid use, infertility, pituitary dysfunction, chronic corticosteroids.

Validated symptom questionnaires (ADAM, AMS) are NOT recommended as screening tools or as surrogates for laboratory testing.[4]


Indications and contraindications

Indication: symptomatic men with confirmed low TT, after shared decision-making regarding benefits and risks.[1]

Absolute and near-absolute contraindications[1][6][7]

CategorySpecific
OncologicBreast cancer; metastatic prostate cancer
Prostate evaluation pendingPalpable prostate nodule or induration without urologic evaluation; PSA >4 ng/mL (>3 ng/mL in high-risk men) without urologic evaluation
HematologicHematocrit >48% (>50% at high altitude) — relative; thrombophilia, active VTE
RespiratoryUntreated severe OSA
LUTSIPSS >19 (severe)
CardiovascularUncontrolled heart failure; MI or stroke within the last 6 months (EMAS extends to 4 months)[7]
FertilityNear-term fertility desire — TRT suppresses spermatogenesis (see below)[1][8]

Formulations — detailed comparison

FormulationTypical doseKey features
Testosterone cypionate / enanthate (IM, short-acting)50–100 mg IM q1–2 wk (or 100–200 mg q2 wk)Inexpensive, widely available; supraphysiologic peaks and symptom troughs; monitor mid-interval TT[5][6]
Testosterone undecanoate (IM, long-acting — Aveed)750 mg IM, repeat at 4 wk, then every 10 wkOnly 4–5 injections/year; FDA boxed warnings for pulmonary oil microembolism (POME), anaphylaxis, and MACE; requires 30-min post-injection observation in a healthcare setting[5]
Testosterone gel 1.62% (AndroGel)40.5 mg (2 pumps) to shoulders / upper arms daily; range 20.25–81 mgSteady-state levels; secondary transfer risk to women and children — wash hands, cover application site[9]
Other gels1% gel 50–100 mg; 2% gel 40–70 mg; axillary solution 60 mgSimilar transfer-risk considerations[6]
Transdermal patch2.5 or 5 mg nightlyRecreates circadian rhythm; skin irritation is the dominant discontinuation driver[5]
Subcutaneous pellets (Testopel)600–900 mg in-office implantation q3–6 moStable levels, no daily maintenance; extrusion 5–10%, infection, difficult removal[5][10]
Oral undecanoate (Jatenzo)237–396 mg PO BID with foodFirst U.S.-approved oral (2019); self-emulsifying delivery bypasses hepatic first-pass; MACE boxed warning; can raise BP[5][6]
Oral — Tlando (225 mg BID), Kyzatrex (100–200 mg BID)Per productAdditional oral options[6]
Nasal gel (Natesto)11 mg per nostril, 2–3×/dayLess suppression of spermatogenesis than other routes (pulsatile delivery, rapid clearance); nasal irritation, frequent dosing[6][10]
Buccal (Striant)30 mg bioadhesive tablet BID to the gum above incisorGum-related AEs in ~16%[6]

Selection principles: injection for cost and efficacy; gel for steady physiology (watch transfer); pellets for adherence-challenged men; undecanoate oral / IM for infrequent dosing at the cost of boxed warnings; Natesto when fertility preservation matters alongside TRT.


Treatment goals and monitoring

Target range: mid-normal (450–600 ng/dL) per the 2025 Eur Urol review, or 300–900 ng/dL per Endocrine Society.[1][11]

Endocrine Society monitoring protocol[1]

ParameterTimingAction thresholds
Serum testosterone3–6 mo, then annuallyAdjust to mid-normal; sampling timing varies by formulation
HematocritBaseline, 3–6 mo, then annuallyIf >54%, stop therapy; evaluate for hypoxia / OSA; restart at reduced dose
PSABaseline (age ≥40), 3–12 mo, then per screening guidelineUrology referral if PSA increase >1.4 ng/mL in 12 mo, confirmed PSA >4 ng/mL, or prostatic abnormality
DREBaseline, 3–12 mo, then per screening guidelineRefer for abnormality
BMD (DXA)After 1–2 y in men with osteoporosisAssess response
Symptoms and AEsEvery visitClinical response and formulation-specific effects

The 2025 Eur Urol review recommends follow-up at 3 months and every 6–12 months thereafter.[11]


Benefits

Sexual function

Consistent improvement in libido and sexual activity. Effect on erectile function is small but statistically significant (SMD 0.16–0.27).[1][12] The 2025 NEJM review is explicit: TRT may not be effective if the main symptom is ED.[3] The Cochrane review (Lee 2024) concluded TRT produces little to no clinically important difference in erectile function vs placebo.[13] Adding testosterone to an optimized PDE5i regimen has not been shown to further improve erectile function in RCTs.[1] See PDE5 inhibitors.

Body composition

Consistently increases lean mass and decreases fat mass. Buratto 2023 meta-analysis (16 RCTs) — significant gains in hip BMD and total lean mass at 6 months; effects less clear at 12 months.[14]

Bone mineral density

Increases areal and volumetric BMD at spine and hip; improves cortical density and thickness.[1][15]

The TRAVERSE fracture substudy paradox: Snyder 2024 reported a 43% increase in clinical fractures with testosterone (3.8% vs 2.8% over 3 years) — predominantly ankle, wrist, and rib fractures, plausibly related to increased physical activity rather than bone deterioration.[16] This result is unexplained by BMD data and counsels caution in framing TRT as a bone-health intervention.

Anemia

TRT corrects unexplained anemia in hypogonadal men; significantly greater proportion achieved hemoglobin increments >1 g/dL in the TTrials.[1]

Mood and energy

Slight improvements in depressive symptoms, mood, and energy; effect sizes are small and not consistently significant across trials.[1][3]

Glycemic outcomes — the T4DM / TRAVERSE contrast

  • T4DM (Wittert 2021, n = 1,007) — 2 years of testosterone undecanoate + a structured lifestyle program reduced progression to T2D by 40% (RR 0.59) in overweight men with IGT, independent of baseline testosterone[17]
  • TRAVERSE diabetes substudy (Bhasin 2024) — testosterone gel without a structured lifestyle program showed no significant difference in prediabetes-to-diabetes progression and no glycemic improvement in established T2D[18]
  • Interpretation: the metabolic benefits of testosterone appear to require a concurrent lifestyle intervention — TRT is not a diabetes drug on its own[19]

Cardiovascular safety — TRAVERSE

TRAVERSE 2023 (Lincoff, NEJM, n = 5,246 men 45–80 y with hypogonadism and established or high CV risk) is the first adequately powered RCT of CV safety:[2]

EndpointTestosteronePlaceboInterpretation
MACE (primary)7.0%7.3%Non-inferior; HR 0.96 (95% CI 0.78–1.17; p < 0.001 for non-inferiority)
Pulmonary embolism0.9%0.5%Higher on testosterone
Atrial fibrillation3.5%2.4%Higher on testosterone
Acute kidney injury2.3%1.5%Higher on testosterone[5]
Clinical fractures3.8%2.8%Higher on testosterone[16]
CV death, MI, stroke, prostate cancer, LUTSNo increase

The Androgen Society 2024 position paper concluded that it has been "conclusively determined" that TRT does not increase heart attack, stroke, or CV death, based on TRAVERSE plus 2 additional large RCTs, multiple smaller RCTs, several large observational studies, and 19 meta-analyses.[20]

Genuine residual signals: pulmonary embolism, atrial fibrillation, and the unexplained fracture signal. Counsel accordingly.


Prostate safety

Prostate cancer risk

AUA 2018 — Strong Recommendation, Grade B: clinicians should inform patients of the absence of evidence linking TRT to prostate cancer development.[4]

  • TRAVERSE prostate substudy (Bhasin 2023) — PCa incidence 0.46% (T) vs 0.42% (placebo); high-grade PCa rare in both arms[21]
  • Baik 2025 Medicare cohort (n = 546,964) — TRT was associated with 16% reduction in PCa hazard (HR 0.84)[22]
  • García-Becerra 2026 meta-analysis of 41 RCTs (n = 11,161) — no statistically significant increase in PCa events (OR 0.88)[23]

TRT after prostate cancer

The AUA states there is inadequate evidence to quantify the risk-benefit ratio in men with PCa history (Expert Opinion).[4] Retrospective evidence increasingly supports cautious use in selected men with low-to-intermediate-risk disease on active surveillance or after definitive treatment (RP or radiation) with stable PSA.[24][25][26]

Saturation model rationale: androgen-receptor-mediated prostate growth plateaus at relatively low testosterone concentrations, so raising testosterone from hypogonadal to mid-normal ranges should not drive incremental tumor growth.[24][27]

BPH / LUTS

TRT has not been shown to worsen LUTS in RCTs; a large retrospective study found a modest 13% increase in BPH-diagnosis hazard — likely detection bias from intensified follow-up.[3][22]


Erythrocytosis — the most common dose-limiting AE

Highest risk with injectable formulations and in older men.[1][6] In T4DM, hematocrit >54% was triggered in 22% of testosterone-treated men (vs 1% placebo).[17]

Endocrine Society protocol: if hematocrit >54%, stop therapy, evaluate for hypoxia and OSA, and reinitiate at a reduced dose once hematocrit is safe.[1] Switching from injectable to transdermal or to Jatenzo reliably lowers the erythrocytosis signal when therapy must be continued.


Fertility — exogenous TRT suppresses spermatogenesis

AUA / ASRM Male Infertility Guideline — Clinical Principle: exogenous testosterone should not be prescribed to men interested in current or future fertility.[8]

Recovery after discontinuation: two-thirds recover sperm within 6 months; ~10% may not recover until the second year; recovery is not guaranteed in previously infertile men.[4]

Fertility-preserving alternatives[28][29][30][10]

AgentMechanismTypical dosingKey features
Clomiphene citrateSERM — blocks estrogen negative feedback → ↑ GnRH/LH/FSH → ↑ endogenous testosterone25–50 mg PO daily or every other dayOff-label; preserves spermatogenesis; inexpensive; oral
hCGLH analog → stimulates Leydig cells1,000–3,000 IU SC 2–3×/weekMaintains intratesticular testosterone; combine with FSH analog for hypogonadotropic hypogonadism
EnclomiphenePure trans-isomer of clomipheneUnder investigationPotentially fewer estrogenic AEs than clomiphene
Nasal testosterone (Natesto)Pulsatile delivery + rapid clearance11 mg per nostril 2–3×/dayMay have less HPT suppression than other TRT routes; limited fertility data

Habous 2018 RCT (n = 282 hypogonadal men) — clomiphene, hCG, and combination therapy were equally effective at restoring testosterone (~223% increase), with combination producing the greatest symptom improvement.[30]

See Androgen adjuncts for the full fertility-preserving armamentarium.


Special populations

The 2025 NEJM review — benefit most likely in men with unequivocal hypogonadism (TT <200 ng/dL with classic symptoms); marginal in age-related decline without consistent symptoms.[3] EMAS position statement 2023 — offer TRT in symptomatic older men with confirmed low testosterone only after explaining uncertainties about long-term safety, and prefer short-acting transdermal preparations for initiation.[7]

Obesity

The most common cause of functional hypogonadism. Weight loss through lifestyle modification is first-line — it raises endogenous testosterone. T4DM showed testosterone augmented a structured lifestyle program, but TRT for diabetes prevention in men without pathologic hypogonadism is premature.[7][11][17]

Cancer survivors (non-prostate)

Per the NCCN Survivorship Guidelines, survivors of non-prostate malignancies who develop hypogonadism after radiation, chemotherapy, or surgery should be evaluated and treated for hormone-related symptoms.[31]


Evidence Summary

DomainEffectStrengthKey source
Libido / sexual desireConsistently improvedStrongMultiple RCTs; Endocrine Society 2018[1]
Erectile functionSmall improvement; inadequate if ED is dominantModerate (Cochrane-moderate)Lee 2024[13]
Body composition↑ Lean mass, ↓ fat massStrongBuratto 2023[14]
Bone mineral densityIncreased at spine and hipStrongNg Tang Fui 2021[15]
Clinical fracturesUnexpectedly increased (43%)Moderate (single large RCT)Snyder 2024 TRAVERSE[16]
AnemiaCorrectedStrongTTrials / Endocrine Society[1]
Mood / depressionSlight improvementLow–Moderate2025 NEJM review[3]
MACENo increase (non-inferiority established)StrongTRAVERSE 2023[2]
Pulmonary embolismIncreasedModerateTRAVERSE[2]
Atrial fibrillationPossibly increasedLow–ModerateTRAVERSE[2]
Prostate cancerNo increase short–mid termStrongTRAVERSE; García-Becerra 2026[21][23]
ErythrocytosisDose-dependent; most common AEStrongMultiple sources[1][17]
Fertility (spermatogenesis)SuppressedStrongAUA/ASRM 2024[8]

Clinical Positioning

  • Confirm TD biochemically before prescribing — two morning fasting TT values below threshold, with symptoms. Do not rely on ADAM / AMS questionnaires.[4]
  • TRAVERSE has resolved the MACE question. TRT does not increase heart attack, stroke, or CV death in hypogonadal men with elevated CV risk.[2][20]
  • Pulmonary embolism, atrial fibrillation, and the unexplained fracture signal remain genuine — counsel patients on these, particularly men with prior VTE, paroxysmal AF, or falls risk.[2][16]
  • For isolated ED as the chief complaint, TRT is not the answer. Libido responds; erectile function does not meaningfully improve on its own, and adding T to PDE5i has not improved ED in RCTs.[3][13]
  • Hematocrit is the dose-limiting lab. Monitor at 3–6 mo then annually; stop at >54%, investigate OSA, and either switch formulation or re-initiate at a lower dose.[1]
  • Do not give TRT to men pursuing near-term fertility. Offer clomiphene 25–50 mg or hCG 1,000–3,000 IU 2–3×/wk instead, or combine — Habous 2018 showed equivalent testosterone recovery with preserved spermatogenesis.[30]
  • Nasal testosterone (Natesto) is the one TRT formulation with a fertility-sparing argument — the pulsatile delivery and rapid clearance spare the HPT axis more than continuous routes.[10]
  • Prostate cancer is not a contraindication to TRT in selected men with low/intermediate-risk disease on AS or post-definitive treatment with stable PSA — the saturation-model rationale, combined with Kaplan, Gibson 2025, and Santucci 2025 retrospective series, supports cautious use with explicit informed consent.[24][25][26]
  • Obesity first — in men with functional hypogonadism from obesity, lifestyle modification is first-line before TRT; T4DM shows TRT can augment a structured program but does not replace it.[11][17]
  • For older men with age-related decline and mild symptoms, prefer transdermal formulations and short courses with explicit reassessment windows — EMAS 2023 framing.[7]
  • PSA increase >1.4 ng/mL in 12 months on TRT triggers urology referral regardless of absolute value; this is the most operationally useful monitoring rule.[1]
  • Secondary transfer from gels is a real issue — patients must wash hands, cover the site, and avoid skin-to-skin contact with women and children until absorbed.[9]

See Also


References

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2. Lincoff AM, Bhasin S, Flevaris P, et al. "Cardiovascular safety of testosterone-replacement therapy (TRAVERSE)." N Engl J Med. 2023;389(2):107–117. doi:10.1056/NEJMoa2215025

3. Bhasin S, Snyder PJ. "Testosterone treatment in middle-aged and older men with hypogonadism." N Engl J Med. 2025;393(6):581–591. doi:10.1056/NEJMra2404637

4. Mulhall JP, Trost LW, Brannigan RE, et al. "Evaluation and management of testosterone deficiency: AUA guideline." J Urol. 2018;200(2):423–432. doi:10.1016/j.juro.2018.03.115

5. Heidelbaugh JJ, Belakovskiy A. "Testosterone replacement therapy for male hypogonadism." Am Fam Physician. 2024;109(6):543–549.

6. De Silva NL, Papanikolaou N, Grossmann M, et al. "Male hypogonadism: pathogenesis, diagnosis, and management." Lancet Diabetes Endocrinol. 2024;12(10):761–774. doi:10.1016/S2213-8587(24)00199-2

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8. Brannigan RE, Hermanson L, Kaczmarek J, et al. "Updates to male infertility: AUA/ASRM guideline (2024)." J Urol. 2024;212(6):789–799. doi:10.1097/JU.0000000000004180

9. US Food and Drug Administration. Testosterone (transdermal / injectable / oral) — prescribing information. Updated 2024-09-30.

10. Kresch E, Patel M, Lima TFN, Ramasamy R. "An update on the available and emerging pharmacotherapy for adults with testosterone deficiency available in the USA." Expert Opin Pharmacother. 2021;22(13):1761–1771. doi:10.1080/14656566.2021.1918101

11. Boeri L, Masterson T, Antonio L, et al. "Testosterone therapy in adult males with hypogonadism." Eur Urol. 2025. doi:10.1016/j.eururo.2025.12.015

12. Diem SJ, Greer NL, MacDonald R, et al. "Efficacy and safety of testosterone treatment in men: an evidence report for a clinical practice guideline by the American College of Physicians." Ann Intern Med. 2020;172(2):105–118. doi:10.7326/M19-0830

13. Lee H, Hwang EC, Oh CK, et al. "Testosterone replacement in men with sexual dysfunction." Cochrane Database Syst Rev. 2024;1:CD013071. doi:10.1002/14651858.CD013071.pub2

14. Buratto J, Kirk B, Phu S, Vogrin S, Duque G. "Safety and efficacy of testosterone therapy on musculoskeletal health and clinical outcomes in men: a systematic review and meta-analysis of randomized placebo-controlled trials." Endocr Pract. 2023;29(9):727–734. doi:10.1016/j.eprac.2023.04.013

15. Ng Tang Fui M, Hoermann R, Bracken K, et al. "Effect of testosterone treatment on bone microarchitecture and bone mineral density in men: a 2-year RCT." J Clin Endocrinol Metab. 2021;106(8):e3143–e3158. doi:10.1210/clinem/dgab149

16. Snyder PJ, Bauer DC, Ellenberg SS, et al. "Testosterone treatment and fractures in men with hypogonadism." N Engl J Med. 2024;390(3):203–211. doi:10.1056/NEJMoa2308836

17. Wittert G, Bracken K, Robledo KP, et al. "Testosterone treatment to prevent or revert type 2 diabetes in men enrolled in a lifestyle programme (T4DM): a randomised, double-blind, placebo-controlled, 2-year, phase 3b trial." Lancet Diabetes Endocrinol. 2021;9(1):32–45. doi:10.1016/S2213-8587(20)30367-3

18. Bhasin S, Lincoff AM, Nissen SE, et al. "Effect of testosterone on progression from prediabetes to diabetes in men with hypogonadism: a substudy of the TRAVERSE randomized clinical trial." JAMA Intern Med. 2024;184(4):353–362. doi:10.1001/jamainternmed.2023.7862

19. Grossmann M, Wittert GA. "Testosterone in prevention and treatment of type 2 diabetes in men: focus on recent randomized controlled trials." Ann N Y Acad Sci. 2024;1538(1):45–55. doi:10.1111/nyas.15188

20. Morgentaler A, Dhindsa S, Dobs AS, et al. "Androgen Society position paper on cardiovascular risk with testosterone therapy." Mayo Clin Proc. 2024;99(11):1785–1801. doi:10.1016/j.mayocp.2024.08.008

21. Bhasin S, Travison TG, Pencina KM, et al. "Prostate safety events during testosterone replacement therapy in men with hypogonadism: a randomized clinical trial." JAMA Netw Open. 2023;6(12):e2348692. doi:10.1001/jamanetworkopen.2023.48692

22. Baik SH, Baye F, Fung KW, Xian H, McDonald CJ. "Association between testosterone replacement therapy and prostatic disorders in elderly hypogonadal men." J Clin Endocrinol Metab. 2025. doi:10.1210/clinem/dgaf504

23. García-Becerra CA, Arias-Gallardo MI, Juárez-García JE, et al. "Cardiovascular and prostate cancer risk associated to testosterone replacement therapy — a systematic review and meta-analysis of 41 randomized controlled trials." Int J Impot Res. 2026. doi:10.1038/s41443-026-01237-4

24. Kaplan AL, Hu JC, Morgentaler A, et al. "Testosterone therapy in men with prostate cancer." Eur Urol. 2016;69(5):894–903. doi:10.1016/j.eururo.2015.12.005

25. Gibson J, George M, Grice P, et al. "Testosterone replacement therapy following definitive treatment for prostate cancer: a scoping review of safety and efficacy." Int J Impot Res. 2025. doi:10.1038/s41443-025-01206-3

26. Santucci J, Stapleton P, Perera M, et al. "Oncological safety of testosterone replacement therapy in men with localised prostate cancer: a systematic review of observational studies." BJU Int. 2025. doi:10.1111/bju.16870

27. Morgentaler A, Caliber M. "Safety of testosterone therapy in men with prostate cancer." Expert Opin Drug Saf. 2019;18(11):1065–1076. doi:10.1080/14740338.2019.1666103

28. Wu YC, Sung WW. "Clomiphene citrate treatment as an alternative therapeutic approach for male hypogonadism: mechanisms and clinical implications." Pharmaceuticals (Basel). 2024;17(9):1233. doi:10.3390/ph17091233

29. American Society for Reproductive Medicine. "Management of nonobstructive azoospermia: a committee opinion." Fertil Steril. 2018;110(7):1239–1245. doi:10.1016/j.fertnstert.2018.09.012

30. Habous M, Giona S, Tealab A, et al. "Clomiphene citrate and human chorionic gonadotropin are both effective in restoring testosterone in hypogonadism: a short-course randomized study." BJU Int. 2018;122(5):889–897. doi:10.1111/bju.14401

31. National Comprehensive Cancer Network. NCCN clinical practice guidelines in oncology: survivorship. Updated 2026-04-08.