What labs should be monitored for a patient on Testosterone Replacement Therapy (TRT)?

Laboratory Monitoring for Patients on Testosterone Replacement Therapy

Patients on Testosterone Replacement Therapy (TRT) should have regular monitoring of testosterone levels, hematocrit/hemoglobin, and PSA with digital rectal examination at baseline, 3-6 months for the first year, and annually thereafter to prevent serious complications. 1

Baseline Assessment Before Starting TRT

• Testosterone levels: Morning measurement (8-10 AM) 2

  • Total testosterone
  • Free testosterone (preferably by equilibrium dialysis)
  • Sex hormone-binding globulin (SHBG) in obese patients

• Prostate health markers:

  • PSA level
  • Digital rectal examination
  • Consider prostate biopsy if PSA >4.0 ng/mL or abnormal digital rectal examination 1

• Hematologic parameters:

  • Hematocrit or hemoglobin

• Additional baseline assessments:

  • Voiding symptoms (history or standardized questionnaire)
  • Sleep apnea history
  • Lipid profile (optional) 1

Monitoring Schedule During TRT

1. Initial follow-up: 1-2 months after starting TRT

   • Assess efficacy of treatment
   • Consider dose adjustment if response is suboptimal 1

2. Regular monitoring:

   • Every 3-6 months during first year
   • Annually thereafter 1, 2

Key Parameters to Monitor

1. Testosterone Levels

• Target range: 450-600 ng/dL (mid to upper-normal range) 2
• Timing of measurement:
  • For injections: Midway between injections (target 500-600 ng/dL)
  • For transdermal preparations: Can be measured at any time 1

2. Hematocrit/Hemoglobin

• Critical threshold: Hematocrit >54% 1, 2
• Action if elevated:
  • Temporarily withhold TRT
  • Reduce dosage
  • Consider phlebotomy 1

Important: Polycythemia is the most common adverse effect of TRT, occurring in up to 44% of patients on injectable testosterone 2, 3. Regular blood donation alone may be insufficient to maintain hematocrit below 54% 3.

3. Prostate Monitoring

• PSA testing at each follow-up visit
• Digital rectal examination at each follow-up visit
• Indications for urologic referral/prostate biopsy:
  • PSA rises above 4.0 ng/mL
  • PSA increases by >1.0 ng/mL in first 6 months
  • PSA increases by >0.4 ng/mL per year thereafter
  • Changes in digital rectal examination 1

4. Additional Monitoring

• Symptomatic response to treatment
• Voiding symptoms
• Sleep apnea symptoms (new onset or exacerbation)
• Gynecomastia 1

Special Considerations

• Injectable testosterone: Monitor for fluctuations in testosterone levels, with peaks 2-5 days after injection and return to baseline by 10-14 days 1

• Transdermal preparations: Monitor for skin reactions (erythema, pruritus) which occur in up to 66% of patch users and 5% of gel users 1

• Liver function: Routine monitoring with liver function tests is unnecessary for intramuscular injections and transdermal preparations 1

• Fertility concerns: Inform patients about decreased fertility during TRT 2

Monitoring Algorithm

1. Baseline labs → Start TRT
2. 1-2 month follow-up: Check testosterone levels, adjust dose if needed
3. 3-6 month intervals (first year): Check testosterone, hematocrit/hemoglobin, PSA, perform DRE
4. Annual monitoring thereafter: Same parameters as above
5. If hematocrit >54%: Withhold TRT, reduce dose, or perform phlebotomy
6. If PSA increases significantly: Refer for urologic evaluation

By following this monitoring protocol, clinicians can maximize the benefits of TRT while minimizing the risk of serious adverse effects such as polycythemia and potential prostate issues.