What laboratory tests are recommended for patients starting Hormone Replacement Therapy (HRT)?

Laboratory Tests for Hormone Replacement Therapy (HRT)

For patients starting Hormone Replacement Therapy (HRT), comprehensive laboratory testing should include thyroid function tests (TSH and free T4), complete blood count, metabolic panel, lipid profile, and hormone levels specific to the type of HRT being initiated. 1, 2

Essential Baseline Laboratory Tests

• Thyroid Function Tests:

  • Thyroid-stimulating hormone (TSH) 1, 2
  • Free thyroxine (free T4) 1, 2
  • Note: Estrogen administration increases thyroid-binding globulin (TBG) levels, which may affect interpretation of thyroid tests 2

• Complete Blood Count (CBC):

  • Essential for monitoring potential effects on blood cell counts 1
  • Particularly important as estrogens can affect coagulation factors 2

• Comprehensive Metabolic Panel:

  • Liver function tests (ALT, AST, alkaline phosphatase) 1
  • Kidney function (BUN, creatinine) 1
  • Electrolytes (including calcium and magnesium) 1
  • Fasting blood glucose 1

• Lipid Profile:

  • Total cholesterol, HDL, LDL, and triglycerides 1, 2
  • Particularly important as estrogens can increase HDL and triglycerides 2

Hormone-Specific Testing

• For Feminizing HRT:

  • Baseline estradiol levels 1
  • Testosterone levels 1
  • Prolactin (if symptoms of hyperprolactinemia present) 1

• For Masculinizing HRT:

  • Baseline testosterone levels 1
  • Estradiol levels (especially if gynecomastia or breast symptoms present) 1
  • Luteinizing hormone (LH) to assess hypothalamic-pituitary-gonadal axis function 1

Additional Tests Based on Risk Factors

• For patients with cardiovascular risk factors:

  • More frequent lipid monitoring 2
  • Assessment of cardiovascular disease risk factors 2

• For patients with diabetes or at risk for diabetes:

  • HbA1c 1
  • Fasting glucose 1

• For patients with liver disease history:

  • More comprehensive liver function testing 2

Monitoring Schedule

• Initial follow-up:

  • Repeat relevant laboratory tests at 3 months after starting HRT 1

• Long-term monitoring:

  • Every 3-6 months during the first year 1
  • Annually thereafter if stable 1

Common Pitfalls and Caveats

• Thyroid function interpretation: Estrogen therapy increases thyroid-binding globulin, which may alter total T4 levels without affecting free T4 or clinical status 2, 3

• Testosterone monitoring: Morning samples provide the most accurate results due to diurnal variation 1

• Liver function tests: Oral estrogens have greater potential for hepatic effects than transdermal preparations; monitoring is particularly important with oral formulations 1, 2

• Prolactin testing: Only necessary if symptoms suggest hyperprolactinemia or pituitary dysfunction 1

• Avoid unnecessary testing: Studies show significant variation in thyroid testing practices, with many unnecessary tests being ordered 4, 5

By following these laboratory monitoring guidelines, clinicians can safely initiate and maintain patients on HRT while minimizing risks and optimizing outcomes.