Primary hypothyroidism resolves after switching from L-thyroxine solid tablets to liquid oral substitution. A rare case without evidence of an underlying gastrointestinal malabsorption syndrome.

A case of refractory primary hypothyroidism is presented. Despite laboratory-guided hormonal substitution, the patient remained hypothyroid. Multiple diagnostic tests ruled out all known causes of levothyroxine malabsorption. Interestingly, clinical and laboratory responding was promptly achieved, after switching the application format from solid tablets to liquid formula.