Can an elevated serum testosterone level of 1398 ng/dL be due to vitamin D deficiency in a patient not using anabolic steroids or exogenous testosterone?

Can Vitamin D Deficiency Cause Elevated Testosterone?

No, vitamin D deficiency does not cause elevated testosterone levels of 1398 ng/dL—in fact, the opposite relationship exists: vitamin D deficiency is associated with lower testosterone, not higher. Your patient's markedly elevated testosterone (normal range approximately 300–1000 ng/dL) requires investigation for other causes, as this level is inconsistent with any known effect of vitamin D status.

The Actual Relationship Between Vitamin D and Testosterone

Evidence from Observational Studies

• Lower vitamin D levels are associated with lower testosterone levels in observational studies, with a positive correlation demonstrated in cross-sectional analyses 1.
• Mendelian randomization analysis in 4,254 Chinese men showed that genetically determined lower 25-hydroxyvitamin D levels causally predict lower total testosterone (causal regression coefficient 0.12 per SD increase in vitamin D, 95% CI 0.02–0.22) 2.

Evidence from Randomized Controlled Trials

• Vitamin D supplementation does not significantly raise testosterone in most well-designed RCTs. Multiple trials using 20,000 IU weekly for 12 weeks in men with low or normal testosterone showed no significant change in total testosterone levels 3, 4.
• A meta-analysis of 17 RCTs found only a modest increase in total testosterone with vitamin D supplementation (WMD 0.38 nmol/L, 95% CI 0.06–0.70), which is clinically insignificant and far too small to explain your patient's level 5.
• In dialysis patients and healthy subjects, cholecalciferol supplementation had no effect on testosterone levels despite normalizing vitamin D status 6.

The Biological Implausibility

• The direction of effect is wrong: vitamin D deficiency would theoretically lower testosterone, not raise it 2, 7.
• Even in the subset of vitamin D–insufficient men (25[OH]D ≤50 nmol/L), supplementation only increased the testosterone-to-LH ratio modestly, suggesting improved Leydig cell efficiency rather than autonomous testosterone overproduction 7.

What Could Explain a Testosterone of 1398 ng/dL?

Exogenous Testosterone or Anabolic Steroids

• Verify the patient is truly not using testosterone or anabolic steroids, including topical gels, patches, injections, or supplements contaminated with androgens. Direct questioning may be insufficient; consider urine steroid profiling if suspicion remains.

Endogenous Overproduction

• Testosterone-secreting tumors (testicular Leydig cell tumor, adrenal adenoma or carcinoma) can produce markedly elevated testosterone 8.
• Congenital adrenal hyperplasia (late-onset 21-hydroxylase or 11β-hydroxylase deficiency) causes androgen excess but typically presents earlier in life 8.
• Polycystic ovary syndrome (PCOS) in biological females can elevate testosterone, but levels rarely exceed 200 ng/dL.

Laboratory or Assay Issues

• Confirm the result with repeat testing using a different assay method (ideally liquid chromatography–mass spectrometry [LC-MS/MS]), as immunoassays can produce falsely elevated results due to cross-reactivity or heterophilic antibodies 9.
• Assay variability can cause 10–20% differences between methods, and classification of samples can vary by 4–32% depending on the assay used 9.

Medications That Inhibit Steroid Metabolism

• Ketoconazole, metyrapone, and other inhibitors of adrenal steroidogenesis can paradoxically increase androgen precursors if they block downstream enzymes, though this typically does not raise testosterone to 1398 ng/dL 8.

Recommended Diagnostic Workup

Immediate Steps

• Repeat total testosterone using LC-MS/MS to confirm the result and rule out assay interference 9.
• Measure LH and FSH: suppressed gonadotropins suggest exogenous testosterone or autonomous production; elevated LH/FSH suggest primary testicular overproduction 7.
• Measure DHEA-S and 17-hydroxyprogesterone to screen for adrenal sources of androgen excess 8.
• Measure sex hormone–binding globulin (SHBG) and calculate free testosterone to assess bioavailable androgen 5.

If Initial Testing Confirms Elevation

• Testicular ultrasound to exclude Leydig cell tumor if LH is suppressed and DHEA-S is normal.
• Adrenal CT or MRI if DHEA-S is elevated (>700 µg/dL) or 17-hydroxyprogesterone is elevated, suggesting adrenal source 8.
• Urine steroid profiling if exogenous steroid use is suspected but denied.

Why Vitamin D Deficiency Is Not the Cause

• The magnitude is wrong: even if vitamin D deficiency lowered testosterone (which it does), correcting deficiency raises testosterone by only 0.38 nmol/L (11 ng/dL) on average—nowhere near the 400–1100 ng/dL excess seen here 5.
• The direction is wrong: vitamin D deficiency is associated with lower, not higher, testosterone 1, 2.
• The mechanism is wrong: vitamin D supports Leydig cell function and may modestly enhance testosterone production when deficient men are repleted, but it does not cause autonomous overproduction 7.

Common Pitfalls to Avoid

• Do not attribute markedly elevated testosterone to vitamin D deficiency—this is biologically implausible and unsupported by evidence 1, 2, 5.
• Do not delay workup for tumor or exogenous steroid use while correcting vitamin D, as these conditions require urgent evaluation.
• Do not rely on a single testosterone measurement without confirming the result with a second assay, preferably LC-MS/MS, given the high potential for assay interference 9.
• Do not assume the patient is being truthful about exogenous testosterone use—many patients underreport or are unaware of contaminated supplements.