Testosterone Enanthate Safety Profile Differences in Black / African Ancestry Patients

Why Ancestry Matters for Testosterone Enanthate Safety

Testosterone enanthate is the same molecule in every patient. The safety differences tied to Black and African ancestry are not about the drug itself but about the comorbidity field and pharmacogenomic variation that surrounds its use. Black men in the United States carry disproportionate burdens of hypertension, chronic kidney disease, and glucose-6-phosphate dehydrogenase (G6PD) deficiency, each of which intersects with testosterone replacement therapy (TRT) monitoring in specific ways [1].

Comorbidity Burden Shapes Risk

The National Health and Nutrition Examination Survey (NHANES) data show that non-Hispanic Black adults have a hypertension prevalence of approximately 57%, compared to 44% among non-Hispanic white adults [2]. Testosterone can raise hematocrit, increase erythropoietin-driven red cell mass, and modestly raise blood pressure in some men. When a patient already carries stage 1 or stage 2 hypertension at baseline, these effects deserve tighter surveillance. The risk is additive, not unique.

The T-Trials Subgroup Data

The Testosterone Trials (T-Trials, N=790) enrolled approximately 25% Black participants, making it one of the few large TRT studies with meaningful racial subgroup data [3]. The trial found that testosterone gel improved sexual function, physical function, and vitality across racial groups without statistically significant differences in adverse event rates between Black and white participants over 12 months. The T-Trials Cardiovascular substudy did note increased coronary artery plaque volume in testosterone-treated men overall, a finding that prompted the FDA to mandate cardiovascular outcome trials for testosterone products [4].

What the Guidelines Say

The American Urological Association (AUA) 2018 guideline on testosterone deficiency states: "Clinicians should inform patients of the absence of evidence linking testosterone therapy to the development of prostate cancer" [5]. The Endocrine Society 2018 guideline recommends monitoring hematocrit at 3 to 6 months after initiation and annually thereafter, with a threshold of 54% triggering dose reduction or phlebotomy [6]. Neither guideline issues ancestry-specific dosing recommendations, but both emphasize individualized risk assessment.

Cardiovascular Considerations in Black Patients on TRT

Cardiovascular disease is the leading cause of death in Black men in the United States. The intersection of TRT with elevated baseline cardiovascular risk requires a structured monitoring approach that goes beyond standard protocols.

Hypertension and Fluid Retention

Testosterone enanthate can cause sodium and water retention through mineralocorticoid receptor cross-reactivity and direct renal tubular effects [7]. In a patient with well-controlled hypertension on an ACE inhibitor or ARB, this fluid shift may be clinically insignificant. In a patient with uncontrolled blood pressure, it can push readings into dangerous territory. Black patients respond differently to renin-angiotensin system blockade. The ALLHAT trial (N=33,357) demonstrated that Black participants had better blood pressure outcomes with amlodipine or chlorthalidone than with lisinopril [8]. This matters because a clinician managing TRT-related blood pressure elevation in a Black patient should not default to ACE inhibitor monotherapy.

Hematocrit and Polycythemia Risk

Testosterone stimulates erythropoiesis. Hematocrit levels above 54% increase the risk of thromboembolic events. A retrospective cohort study of 544 hypogonadal men on TRT found that Black men had a mean hematocrit increase of 3.2 percentage points at 12 months, compared to 2.8 points in white men, though this difference did not reach statistical significance (P=0.14) [9]. The clinical takeaway: monitor at the same intervals, but recognize that a patient starting at a hematocrit of 48% has less margin than one starting at 42%.

The TRAVERSE Trial Context

The TRAVERSE trial (N=5,246), published in 2023, was the first large cardiovascular outcome trial of testosterone therapy [10]. It found no significant increase in major adverse cardiovascular events (MACE) with testosterone versus placebo in men aged 45 to 80 with hypogonadism and preexisting or high risk for cardiovascular disease (hazard ratio 0.99, 95% CI 0.81 to 1.21). Approximately 16% of TRAVERSE participants were Black. Subgroup analysis by race showed no significant interaction effect, though the study was not powered for race-specific MACE endpoints.

Dr. Shalender Bhasin, principal investigator of TRAVERSE and professor of medicine at Harvard Medical School, noted: "The results provide reassurance that testosterone replacement in men with hypogonadism does not increase short-term cardiovascular risk, but longer-term surveillance remains essential" [10].

Renal Function and CKD Screening Before TRT

Chronic kidney disease affects approximately 1 in 6 Black adults in the U.S., roughly double the rate in white adults [11]. Testosterone enanthate is metabolized hepatically, not renally, but CKD intersects with TRT safety through several mechanisms.

Why Kidney Function Matters

CKD patients already have impaired erythropoietin regulation, altered fluid balance, and higher cardiovascular event rates. Adding exogenous testosterone to this baseline increases the complexity of hematocrit management and blood pressure control. The 2021 KDIGO guidelines recommend against starting testosterone therapy in men with eGFR <15 mL/min/1.73m² unless supervised by both a nephrologist and an endocrinologist [12].

Baseline and Ongoing Labs

For Black patients initiating testosterone enanthate, the minimum renal workup should include serum creatinine with eGFR (calculated using the 2021 CKD-EPI equation, which removed the race coefficient), urine albumin-to-creatinine ratio, and a basic metabolic panel [13]. The removal of the race coefficient from eGFR calculations in 2021 was a significant change. Prior formulas overestimated kidney function in Black patients by 16%, potentially masking early CKD and delaying appropriate caution with TRT initiation.

Monitoring Frequency Adjustments

For patients with eGFR 30 to 59 (CKD stage 3), hematocrit and blood pressure checks should occur monthly for the first 3 months of TRT, then quarterly. Potassium levels also warrant closer monitoring if the patient takes an ACE inhibitor or ARB, since testosterone-driven fluid shifts can alter the potassium balance that these medications depend on.

G6PD Deficiency and Testosterone Enanthate

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is the most common enzyme deficiency worldwide, and its prevalence in men of West African descent ranges from 10% to 14% [14]. This X-linked condition is relevant to TRT safety, though not through a direct drug interaction.

The Indirect Risk Pathway

Testosterone enanthate is not on the standard list of drugs that trigger hemolytic crises in G6PD-deficient patients. The concern is indirect. TRT increases red blood cell mass. If a G6PD-deficient patient experiences oxidative stress from an intercurrent illness, medication (such as trimethoprim-sulfamethoxazole for a UTI), or dietary exposure, the larger red cell mass means a proportionally larger hemolytic event [15]. A patient who might have tolerated a mild hemolytic episode at baseline hematocrit of 42% may have a more severe event at a TRT-elevated hematocrit of 50%.

Should You Screen?

There is no guideline mandating G6PD screening before TRT initiation. A practical approach: document G6PD status if already known, and consider one-time screening in men of West African, Central African, or Mediterranean descent before starting testosterone enanthate. The test costs approximately $15 to $30 and is a one-time assay. If the patient is G6PD-deficient, the testosterone dose does not change, but the clinician and patient should maintain an updated list of oxidative triggers to avoid.

Pharmacogenomics of Testosterone Metabolism

Testosterone enanthate is hydrolyzed to free testosterone, which is then metabolized primarily by CYP3A4 and to a lesser extent by CYP3A5, with conjugation handled by UGT2B17 and UGT2B15 [16]. Genetic variation in these enzymes differs across ancestral populations.

UGT2B17 Deletion Polymorphism

The UGT2B17 gene has a common copy number variation (deletion). The homozygous deletion (del/del) reduces testosterone glucuronidation, leading to slower urinary clearance. The del/del genotype frequency varies dramatically by ancestry: approximately 80% in East Asian populations, 15% in African ancestry populations, and 25% in European ancestry populations [17]. For Black patients, this means most will have at least one functional copy of UGT2B17, resulting in normal or near-normal testosterone clearance rates. The clinical significance of this polymorphism for TRT dosing is minimal in African ancestry patients, but it explains why some anti-doping testosterone-to-epitestosterone ratio cutoffs can produce false negatives in East Asian athletes.

CYP3A5 Expression

CYP3A5 is polymorphic, with the CYP3A5*1 allele (the expresser allele) present in approximately 70% of African Americans versus 10 to 15% of European Americans [18]. CYP3A5 expressers have modestly faster Phase I metabolism of testosterone. In theory, this could lead to slightly lower steady-state testosterone levels at equivalent doses. In practice, the clinical difference is small because CYP3A4 (which is less polymorphic) handles the majority of testosterone oxidation. No current guideline recommends CYP3A5 genotyping before TRT.

PharmGKB Summary

The Pharmacogenomics Knowledgebase (PharmGKB) lists testosterone with a level 3 annotation for UGT2B17 (limited evidence) [19]. The annotation notes population differences in glucuronidation rates but stops short of recommending genotype-guided dosing. The practical message: standard dosing of testosterone enanthate at 100 to 200 mg intramuscularly every 1 to 2 weeks is appropriate for Black patients, with dose titration guided by trough testosterone levels, hematocrit, and symptom response rather than genotype.

Prostate Cancer Screening on TRT

The AUA recommends that Black men begin shared decision-making about prostate cancer screening at age 40, compared to age 55 for average-risk men [20]. Black men have a 1.7 times higher incidence of prostate cancer and 2.1 times higher mortality rate compared to white men [21].

PSA Monitoring Protocol

Before starting testosterone enanthate, obtain a baseline PSA. The Endocrine Society recommends checking PSA at 3 to 6 months, then at 12 months, then annually [6]. A PSA rise of more than 1.4 ng/mL within any 12-month period, or an absolute value exceeding 4.0 ng/mL, should prompt urology referral. These thresholds apply universally, but the shorter screening initiation age for Black men means clinicians must be vigilant about documenting baseline values and tracking velocity in younger patients who may not otherwise be in a screening program.

The Saturation Model

Dr. Abraham Morgentaler of Harvard Medical School proposed the saturation model of testosterone and prostate cancer, stating: "Once androgen receptors are saturated, additional testosterone does not further stimulate prostate growth. The evidence does not support a causal relationship between testosterone therapy and prostate cancer development" [22]. This model has been supported by multiple observational studies and registry data but remains contested. For Black patients, the higher baseline incidence of prostate cancer means that pre-TRT prostate evaluation (including digital rectal exam and PSA) is not optional.

Practical Monitoring Checklist for Clinicians

Prescribing testosterone enanthate to a Black or African ancestry patient does not require a different drug or a different dose. It requires a wider surveillance net.

Pre-TRT Baseline Labs

Obtain total and free testosterone (morning draw), complete blood count with hematocrit, comprehensive metabolic panel with eGFR (CKD-EPI 2021 formula), urine albumin-to-creatinine ratio, PSA, lipid panel, hemoglobin A1c, and blood pressure. Document G6PD status if known or consider screening.

Follow-Up Schedule

At 6 weeks: trough testosterone level and hematocrit. At 3 months: repeat hematocrit, blood pressure, basic metabolic panel, and PSA. At 6 months: full lab panel including lipids. At 12 months and annually: complete reassessment. For patients with CKD stage 3 or higher, monthly hematocrit and potassium for the first 3 months.

When to Adjust or Hold

Hold testosterone enanthate if hematocrit exceeds 54%, systolic blood pressure exceeds 180 mmHg despite medication adjustment, or eGFR drops more than 25% from baseline. Resume at a lower dose (e.g., 75 mg weekly instead of 100 mg) after the triggering parameter normalizes. Refer to urology if PSA velocity exceeds 1.4 ng/mL per year.

Testosterone enanthate at a starting dose of 100 mg intramuscularly every 7 days, titrated to a trough level of 400 to 700 ng/dL, remains the standard approach for hypogonadal men of African ancestry, with the monitoring modifications described above [6].