Sermorelin in Patients with Hypothyroidism
Sermorelin should not be used in patients with hypothyroidism unless thyroid function is adequately controlled with levothyroxine replacement therapy, as it may worsen thyroid dysfunction or mask central hypothyroidism.
Relationship Between Growth Hormone and Thyroid Function
Growth hormone (GH) and thyroid hormones have significant interactions that affect patient outcomes:
- GH therapy or GH secretagogues like sermorelin can unmask central hypothyroidism in 36-47% of patients with pituitary disorders 1, 2
- GH replacement causes significant reductions in serum T4 levels without compensatory increases in T3 or TSH 1
- Patients with multiple pituitary hormone deficiencies are at highest risk for developing worsened thyroid function after starting GH therapy 2
Clinical Considerations for Sermorelin Use
Pre-Treatment Assessment
- Evaluate thyroid function with TSH and free T4 before initiating sermorelin therapy
- Ensure adequate thyroid hormone replacement in hypothyroid patients before starting sermorelin
- Patients with "low-normal" T4 levels should be considered for thyroid replacement prior to starting GH or GH secretagogues 1
Monitoring During Treatment
- Monitor thyroid function (TSH and free T3) every 3-6 months during sermorelin therapy 3
- Watch for signs of worsening hypothyroidism: increased fatigue, cold intolerance, constipation, dry skin, weight gain
- Adjust levothyroxine dosage as needed to maintain euthyroid state
Risk Factors for Thyroid Dysfunction with Sermorelin
- Multiple pituitary hormone deficiencies
- History of pituitary or hypothalamic disease
- Lower baseline serum T4 concentration
- Central (secondary) hypothyroidism
Clinical Implications
Patients who develop worsened hypothyroidism after starting GH therapy show:
- Less improvement in quality of life compared to those who remain euthyroid 1
- Potential for increased cardiovascular risk if hypothyroidism is not adequately treated 3
Special Considerations
Chronic Kidney Disease
- In patients with CKD, thyroid hormone levels (TSH and free T3) should be monitored regularly during GH therapy 3
- GH therapy should be stopped in patients with persistent severe secondary hyperparathyroidism (PTH >500 pg/ml) 3
Contraindications
- Sermorelin should not be initiated in patients with untreated hypothyroidism
- Growth hormone secretagogues like sermorelin lack FDA approval for human use and have insufficient safety data 4
Conclusion
While sermorelin can theoretically be used in patients with hypothyroidism, it should only be considered after thyroid function is optimized with appropriate levothyroxine replacement. Close monitoring of thyroid function is essential during treatment, with prompt adjustment of thyroid hormone replacement as needed.