Refractory hypothyroidism: Diagnostic evaluation and management strategies

Area of Science:

• Endocrinology
• Gastroenterology

Background:

• Refractory hypothyroidism is defined by elevated levothyroxine requirements (>1.9-2.5 μg/kg/day).
• Its prevalence remains undefined, and it is distinct from thyroid hormone resistance.

Purpose of the Study:

• To define refractory hypothyroidism and explore its common and less common causes.
• To outline diagnostic approaches for identifying the etiology of refractory hypothyroidism.

Main Methods:

• Review of medical literature and clinical guidelines.
• Analysis of patient history, clinical examination findings, and diagnostic test results.
• Focus on differentiating non-compliance from malabsorption and identifying underlying digestive pathologies.

Main Results:

• Common causes include non-compliance (pseudomalabsorption) and malabsorption.
• Malabsorption can stem from food/medication interactions or digestive conditions (gastritis, celiac disease, lactose intolerance, surgery).
• Less frequent causes involve increased thyroid hormone degradation via type 3 deiodinase (tumors, tyrosine kinase inhibitors).

Conclusions:

• Medical history and clinical examination are crucial for etiological investigation.
• Screening for deficiencies and autoimmune diseases can indicate digestive pathology.
• Levothyroxine absorption tests can confirm malabsorption, potentially avoiding invasive procedures.