Patterns of thyroid hormone levels in pediatric medullary thyroid carcinoma patients on vandetanib therapy

Background Tyrosine kinase inhibitors (TKIs) have been associated with elevated TSH as a drug class effect. Prior studies of vandetanib in adults with medullary thyroid carcinoma (MTC) described an increase in levothyroxine (LT) requirement. We studied TSH, free T4, and LT dosing in children and adolescents enrolled in the phase I/II trial of vandetanib for medullary thyroid cancer (MTC)