Testosterone Enanthate in Black / African Ancestry Patients: Documented Efficacy Gaps Explained

Why Ethnicity Matters for Testosterone Enanthate Therapy

Testosterone enanthate (TE) is an intramuscular depot ester that releases testosterone over 7 to 10 days. The drug itself does not change by race. What changes is the biological environment the drug enters: receptor sensitivity, carrier-protein concentrations, metabolic enzyme activity, and the pre-existing burden of comorbidities that amplify or blunt the therapy's effects.

The American Urological Association's 2018 guideline on testosterone deficiency states that clinicians should interpret testosterone levels "in the context of the individual patient's symptoms, signs, and other laboratory findings," a framework that logically extends to ancestry-linked variation in those same laboratory reference ranges. That principle has not yet been operationalized into ancestry-specific dosing algorithms for TE, which is where the current evidence gap sits.

The Data Scarcity Problem

The T-Trials, published in the New England Journal of Medicine in 2016 (N=790 men, aged 65 and older), remain the highest-quality placebo-controlled evidence base for testosterone therapy in older men [1]. Black men made up fewer than 5% of that cohort. The TRAVERSE cardiovascular outcomes trial (N=5,246, NEJM 2023) was larger, but its racial subgroup data have not been published in a form that allows independent efficacy modeling for Black men [2].

That absence of representative trial data is itself a clinical fact. Prescribers cannot simply assume that a dosing target of 500 to 700 ng/dL total testosterone, calibrated on predominantly white cohorts, produces the same symptomatic or metabolic outcome in a Black patient with lower SHBG and shorter androgen receptor CAG repeats.

What Population Pharmacogenomics Shows

PharmGKB and the Pharmacogenomics Knowledgebase list several gene-drug relationships relevant to androgen metabolism that carry population-frequency differences across ancestry groups [3]. The key genes include AR (androgen receptor), CYP19A1 (aromatase), SHBG, and SRD5A2 (5-alpha reductase type 2).

Sex Hormone-Binding Globulin and Free Testosterone Discordance

Lower SHBG in Black men is one of the most replicated findings in endocrinology. This directly undermines total-testosterone-based dosing for TE.

A 2012 analysis from the Third National Health and Nutrition Examination Survey (NHANES III) found that Black men had mean SHBG concentrations approximately 16% lower than non-Hispanic white men after adjusting for age, BMI, and insulin resistance [4]. Lower SHBG means a larger fraction of circulating testosterone is free or albumin-bound, and therefore biologically active.

Clinical Consequence: Apparent Eugonadism at Lower Total T

A Black patient with a total testosterone of 380 ng/dL and SHBG of 18 nmol/L may have free testosterone well within the normal range. The same total T in a white patient with SHBG of 32 nmol/L could represent true functional hypogonadism. Treating both with identical TE doses to reach the same total-T target will systematically over-treat the Black patient.

Clinicians using the Vermeulen equation or direct equilibrium dialysis for free T measurement before initiating TE get a far more accurate picture. The Endocrine Society's 2018 Clinical Practice Guideline on male hypogonadism recommends calculating or measuring free testosterone when SHBG is expected to be abnormal, and low SHBG is precisely that abnormality in this population [5].

Practical Dosing Implications

Standard TE dosing runs 100 to 200 mg intramuscularly every 7 to 14 days. In Black men with confirmed low SHBG, starting at the lower bound of 100 mg every 10 days and titrating to free-T targets rather than total-T targets is a more defensible approach. Trough and peak draws at weeks 6 to 8 should include both total T and calculated free T. Targeting a calculated free T of 9 to 20 ng/dL aligns with Endocrine Society guidance and corrects for the SHBG confound [5].

Androgen Receptor CAG Repeat Polymorphism

The androgen receptor gene (AR) on the X chromosome contains a polymorphic CAG trinucleotide repeat in exon 1. Shorter repeat lengths correlate with greater AR transactivation, meaning the receptor responds more strongly to the same androgen concentration.

African ancestry populations carry, on average, shorter CAG repeat lengths than European ancestry populations. A 2001 study by Irvine et al. In Cancer Epidemiology, Biomarkers and Prevention (N=162 men across four ethnic groups) reported mean CAG repeats of 18.1 in Black men versus 21.6 in white men [6]. That three-repeat difference is enough to shift dose-response curves.

Androgenic Sensitivity at Lower Serum T

The practical upshot: a Black patient starting TE may reach full androgenic effect at a lower serum testosterone concentration than a white patient. Erythrocytosis, acne, and prostate-specific antigen (PSA) rise may appear at trough testosterone levels that would be considered sub-therapeutic in standard white-derived reference ranges.

Monitoring hematocrit at baseline, then at 3 months and 6 months after TE initiation, is standard practice. In patients with shorter AR CAG repeats (which can now be tested clinically through commercial pharmacogenomic panels), that interval should tighten to every 8 to 10 weeks in the first year.

Prostate Cancer Risk Context

Black men face prostate cancer incidence approximately 70% higher and mortality approximately 2.1 times higher than white men in the United States [7]. Exogenous testosterone does not cause prostate cancer per current evidence, but TE therapy in the setting of subclinical or established prostate disease is a separate concern. PSA should be checked at baseline, 3 months, and 12 months after starting TE, with a lower threshold for urology referral: a PSA rise of more than 1.4 ng/mL in any 12-month period, or any absolute PSA above 4.0 ng/mL [5].

Cardiovascular and Hypertension Risk in Black Patients on TE

Hypertension prevalence among Black American adults exceeds 54%, compared with 46% in white Americans, according to CDC 2023 surveillance data [8]. Testosterone enanthate raises hematocrit, can worsen sleep apnea, and transiently increases systolic blood pressure, each of which compounds the already-elevated cardiovascular risk in this population.

TRAVERSE Trial Findings and Their Limits

The TRAVERSE trial (N=5,246, mean age 57.5 years, all with pre-existing or high-risk cardiovascular disease) found that testosterone therapy was non-inferior to placebo for major adverse cardiovascular events over a median follow-up of 33 months [2]. The primary endpoint hazard ratio was 0.96 (96% CI 0.78 to 1.17). However, testosterone increased atrial fibrillation (3.5% vs. 2.4%), acute kidney injury (2.3% vs. 1.5%), and pulmonary embolism (0.9% vs. 0.5%) rates compared with placebo.

Atrial fibrillation and hypertensive nephropathy are already disproportionately prevalent in Black patients. A Black man with Stage 2 hypertension starting TE deserves a frank cardiovascular risk conversation before the first injection, including blood pressure optimization to below 130/80 mmHg per the 2017 ACC/AHA guideline before TE is initiated [9].

Renin-Angiotensin-Aldosterone Axis Differences

A well-documented pharmacological phenomenon: ACE inhibitors and ARBs produce smaller blood pressure reductions in Black patients on average than in white patients, primarily because of lower renin activity in hypertension common to African ancestry populations. This means Black patients on TE who develop hypertension on therapy may not respond as well to the first-line antihypertensive agents typically co-prescribed. Thiazide diuretics and calcium channel blockers remain more effective first-line choices in this group per JNC 8 and AHA guidance [9].

Prescribers adjusting TE dose in a Black patient with worsening hypertension should not assume standard renin-suppressive therapies will fully cover the incremental BP burden of testosterone.

G6PD Deficiency: A Rarely Discussed Variable

Glucose-6-phosphate dehydrogenase (G6PD) deficiency affects approximately 11 to 13% of Black American men. It is X-linked, so hemizygous males express the full phenotype [10]. G6PD is the rate-limiting enzyme in the pentose phosphate pathway and protects red blood cells from oxidative damage.

Testosterone at pharmacologic doses increases erythropoiesis and raises hematocrit, typically by 3 to 7 percentage points after 6 months of TE therapy. In G6PD-deficient men, the combination of elevated hematocrit, increased red cell oxidative burden, and exposure to certain co-medications (dapsone, primaquine, some sulfonamides) can trigger hemolytic episodes.

Screening and Management

G6PD status is not part of standard pre-TRT labs in any major guideline as of 2025. For Black men starting TE, baseline G6PD screening is a reasonable addition, especially in patients with a personal or family history of hemolysis or jaundice with drug exposure. If G6PD deficiency is confirmed, hematocrit thresholds for dose reduction should be tightened: consider reducing TE dose if hematocrit exceeds 50% rather than the standard 54% cutoff.

Pharmacogenomic Testing in Clinical Practice

The following framework summarizes how ancestry-linked variables should modify standard TE management decisions in Black and African ancestry patients. This is an original HealthRX clinical decision framework developed for this population gap, intended to be reviewed and approved by the HealthRX physician panel before clinical deployment.

Pre-initiation checklist for Black / African ancestry patients starting TE:

1. Measure both total testosterone and SHBG. Calculate free testosterone using the Vermeulen equation. Do not rely on total T alone.
2. Establish baseline hematocrit, CBC, PSA, blood pressure, and renal function (eGFR plus urine albumin-to-creatinine ratio given elevated CKD risk).
3. Consider G6PD screening, particularly if personal or family history suggests prior hemolytic episodes.
4. Consider commercial AR CAG repeat pharmacogenomic testing if available. Shorter repeats (below 20) should lower your target total-T range by approximately 50 to 80 ng/dL and tighten monitoring intervals.
5. Optimize blood pressure to below 130/80 mmHg before the first injection. Prefer calcium channel blockers or thiazides over ACE inhibitors as first-line if antihypertensive initiation is needed concurrently.
6. Document baseline PSA. Set a lower referral threshold: any PSA rise greater than 1.4 ng/mL in 12 months warrants urology consultation.

Monitoring modifications during TE therapy:

• Hematocrit at weeks 6 to 8, then every 3 months for the first year (versus the standard 6-month schedule used in lower-risk populations).
• Free testosterone at trough (day of injection) at week 8. Target free T of 9 to 15 ng/dL rather than pushing to the upper normal range.
• PSA at 3 months and 12 months, with annual checks thereafter.
• Blood pressure at every clinical contact.

Aromatization, Estradiol, and Body Composition Differences

CYP19A1 encodes aromatase, the enzyme that converts testosterone to estradiol. Population-level differences in CYP19A1 single-nucleotide polymorphisms (SNPs) affect aromatization rates. African ancestry populations show distinct CYP19A1 SNP frequencies compared with European ancestry populations, though the net direction of effect on estradiol levels in men on TE is not yet definitively established in large ethnicity-stratified studies [3].

What is established: Black men in the United States carry higher rates of obesity (CDC BRFSS 2023: 49.9% age-adjusted obesity prevalence in Black adults vs. 41.4% in white adults), and adipose tissue is the primary site of peripheral aromatization. A heavier aromatizer on TE will convert more testosterone to estradiol, potentially blunting androgenic benefit (libido, muscle mass, erythropoiesis) while amplifying estrogen-mediated effects (gynecomastia, fluid retention, HDL modulation).

Estradiol Monitoring

Estradiol (sensitive LC-MS/MS assay, not the standard immunoassay) should be measured at the 8-week trough check. Target estradiol in men on TRT is generally 20 to 40 pg/mL. Black men with BMI above 35 starting TE may aromatize enough to exceed 60 pg/mL, at which point co-prescribing anastrozole 0.25 to 0.5 mg twice weekly is a reasonable clinical consideration, titrated to estradiol response rather than a fixed dose.

Baseline Testosterone Reference Ranges: Are They Biased?

Most laboratory reference ranges for total testosterone (typically 300 to 1,000 ng/dL) were derived from predominantly white male cohorts. A 2013 analysis of NHANES data by Travison et al. Found that Black men had modestly higher total testosterone at younger ages but that differences narrowed considerably after adjusting for BMI, smoking, and alcohol use [11]. The 2.5 to 4.9% raw difference in unadjusted total T does not translate into a meaningfully different functional normal range once SHBG and metabolic confounders are accounted for.

The clinical risk is this: a Black patient with symptoms of hypogonadism and a total testosterone of 340 ng/dL may be told he is "normal" because he falls above the 300 ng/dL lab cutoff, when his free testosterone is low and his AR CAG repeats amplify his symptomatic burden. Conversely, a Black patient with total T of 290 ng/dL and short CAG repeats may be fully androgenically sufficient by receptor sensitivity.

Treating the number without the biological context is a prescription for both under-treatment and over-treatment in this population.

What the T-Trials Did and Did Not Tell Us

The T-Trials consortium published results across seven separate trials in 2016 in the New England Journal of Medicine (N=790 men, all 65 years or older, all with total testosterone below 275 ng/dL at baseline) [1]. Testosterone gel, not enanthate, was the active drug, but the mechanistic lessons transfer. Testosterone therapy improved sexual function, walking distance, bone mineral density, and anemia correction versus placebo.

Black men were enrolled at rates far below their population prevalence of hypogonadism. The investigators did not publish race-stratified efficacy or safety data at the primary report stage. A 2021 secondary analysis attempted to examine race as a moderator of testosterone response but was limited by the small number of Black participants.

The lesson is not that TE is unsafe in Black men. The lesson is that we are extrapolating efficacy and safety data from a population that did not adequately include them, which demands more individualized monitoring and lower thresholds for dose adjustment.

Chronic Kidney Disease Risk and Testosterone

Black Americans develop end-stage renal disease at 3.7 times the rate of white Americans, driven by hypertension, diabetes, and APOL1 gene variants [12]. CKD alters testosterone metabolism in two ways: it reduces SHBG production (further lowering total T while free T may remain relatively preserved), and it increases cardiovascular risk.

Starting TE in a patient with eGFR below 45 mL/min/1.73m2 requires nephrology input. Testosterone-driven erythrocytosis combined with reduced renal clearance of the metabolic byproducts of accelerated erythropoiesis can accelerate renal decline. Hematocrit targets in CKD stage 3b or worse should remain below 50%, with TE dose reduction or extended injection intervals (every 14 days rather than 7) to flatten the pharmacokinetic peak.