What labs should be drawn for a patient on Testosterone Replacement Therapy (TRT) and when?

Laboratory Monitoring for Testosterone Replacement Therapy

The patient should have comprehensive TRT monitoring labs drawn on 11/11, including total testosterone (trough), estradiol, CBC with hematocrit, CMP, PSA, and Factor VIII activity. 1

Recommended Laboratory Tests and Timing

Essential Tests for 11/11 (6-Week Follow-up)

• Total Testosterone (trough) - Draw before next injection to assess minimum levels 1

  • Target range: 700-900 ng/dL (currently 1015 ng/dL - supraphysiologic) 1
  • Should be drawn in early morning for consistency 1

• Estradiol (LC/MS) - Currently elevated at 35 pg/mL 1

  • Important to monitor due to aromatization of testosterone to estradiol, especially with dose changes 1
  • Elevated estradiol may contribute to irritability symptoms 2

• Complete Blood Count (CBC) with differential 1

  • Hematocrit is a critical safety parameter (currently 49.1%, increased from 44.3%)
  • Intervention required if Hct reaches ≥52% 1
  • Injectable testosterone has greatest risk for erythrocytosis 1

• Comprehensive Metabolic Panel (CMP) 1

  • To monitor potassium (currently elevated at 5.6 mmol/L)
  • To assess renal function (current eGFR 66)

• Prostate-Specific Antigen (PSA) 1

  • Currently elevated at 5.5 ng/mL (from 2.9 ng/mL)
  • Critical to monitor due to recent elevation and urology involvement
  • Per urology recommendation for repeat in 6 weeks

• Factor VIII Activity 1

  • Currently elevated at 159% (ref 56-140%)
  • Important to determine if elevation is persistent vs. transient

Timing Considerations

• Draw labs at trough level (just before next scheduled injection) 3
• Patient should be well-hydrated and avoid strenuous exercise for 48 hours before blood draw 3
• Avoid fist clenching during blood draw to prevent spurious potassium elevation 4

Monitoring Schedule

Immediate Follow-up

• Potassium should be rechecked immediately to rule out hemolysis vs. true hyperkalemia 1

6-Week Follow-up (11/11)

• Complete panel as detailed above 1

Long-term Monitoring

• Once stable, monitor every 3-6 months 1
• Annual monitoring should continue indefinitely while on TRT 5

Special Considerations

Hematocrit Monitoring

• Hematocrit >50% warrants careful evaluation 1
• Hematocrit ≥52% requires dose reduction or temporary discontinuation 1
• Patient's current level (49.1%) requires close monitoring but not immediate intervention 1

PSA Monitoring

• Two consecutive elevated PSA levels warrant urological evaluation 1
• Current elevation is being monitored by urology with "watchful waiting" approach 1
• Follow urology recommendations for repeat testing 1

Factor VIII Monitoring

• Elevated Factor VIII (159%) requires repeat testing to determine if persistent 1
• If persistently >160%, hematology re-consultation is warranted 1
• Transient elevations can occur from exercise, inflammation, or as physiologic TRT effect 6

Pitfalls to Avoid

• Inconsistent laboratory testing: Use the same laboratory for serial estradiol measurements due to variability between labs 2
• Improper timing: Testosterone levels fluctuate significantly with injectable formulations; trough measurements provide the most conservative assessment 3
• Overlooking estradiol: High estradiol can cause irritability and other symptoms even when testosterone is in range 1, 2
• Ignoring hematocrit: Most common serious adverse effect of TRT is erythrocytosis 1
• Inadequate PSA monitoring: PSA increases require careful evaluation, especially with recent elevation 1

By following this comprehensive monitoring approach, you can safely manage this patient's TRT while minimizing risks and optimizing benefits.