Can I test a patient's testosterone level?

Testing Testosterone Levels in Patients

Testosterone testing is recommended for all men diagnosed with organic erectile dysfunction, especially in those for whom PDE5 inhibitor therapy has failed. 1

Indications for Testosterone Testing

• Primary indications:

  • Erectile dysfunction (ED) 1
  • Symptoms of hypogonadism 2
  • Assessment of cardiovascular risk in men with ED 1

• Specific patient populations who should be tested:

  • Men with diabetes who have symptoms or signs of low testosterone 1
  • Men seeking consultation for sexual dysfunction 1
  • Men with organic ED regardless of PDE5 inhibitor response 1

Testing Procedure and Methodology

Collection Timing

• Morning collection is essential (8-11 AM) due to circadian variation 3
• Blood drawn between 8-11 AM shows significantly higher levels (411.7 ng/dL) compared to afternoon/evening draws (368.3 ng/dL) 3
• If needed, the collection window may be extended to include 11 AM-2 PM, as values don't differ significantly from the 8-11 AM window 3

Recommended Testing Protocol

1. Obtain fasting morning samples on two or more occasions 4
2. Measure total testosterone using reliable assay methods 5
3. Consider free testosterone measurement when:
   • Alterations in binding protein concentrations are suspected
   • Total testosterone levels are borderline (slightly above or below normal range) 5
   • To clarify borderline results 6

Preferred Laboratory Methods

• Gold standard: Liquid chromatography-tandem mass spectrometry (LC-MS/MS) 4
• Use laboratories certified by accuracy-based programs (e.g., CDC's Hormone Standardization Program) 4
• For free testosterone, equilibrium dialysis is the preferred method 4
• Avoid immunoassays for women or men with borderline low levels due to accuracy issues 6

Additional Testing Considerations

When Evaluating Erectile Dysfunction

• Include testosterone testing as part of a comprehensive cardiovascular risk assessment 1
• Consider additional tests:
  • Resting electrocardiogram
  • Blood pressure measurement
  • Waist circumference and BMI 1

For Diabetic Patients

• Morning total testosterone measurement is recommended for men with diabetes showing symptoms of hypogonadism 1
• Consider free testosterone calculations using total testosterone, sex hormone binding globulin, and albumin concentrations for borderline cases 1

Interpretation and Follow-up

Target Ranges

• Normal total testosterone range: 300-1000 ng/dL 7
• Target range for replacement therapy: 450-600 ng/dL 2

Monitoring Parameters

If low testosterone is identified and treatment initiated:

• Monitor testosterone levels, hematocrit, and PSA every 3-6 months during first year of treatment 2
• Watch for hematocrit exceeding 54%, which requires therapy discontinuation 2
• Monitor PSA for increases >1.0 ng/mL in any one year 2

Common Pitfalls to Avoid

1. Timing errors: Afternoon testing can falsely suggest hypogonadism due to natural circadian variation 3
2. Single sample reliance: Testosterone levels vary day-to-day; multiple samples are recommended 4
3. Using unreliable assays: Immunoassays often lack accuracy, especially at lower ranges 6
4. Ignoring binding protein variations: Total testosterone may be misleading when binding proteins are altered 5
5. Failing to consider obesity: This is a major confounder in testosterone level interpretation, especially in diabetic men 1

By following these evidence-based guidelines for testosterone testing, you can accurately identify patients with hypogonadism and provide appropriate treatment recommendations.