Macro-TSH in patients with primary hypothyroidism due to autoimmune thyroiditis

Abstract

Thyroid stimulating hormone (TSH) is one of the key indicators in the diagnosis of the thyroid gland functional disorders. Minor changes in TSH concentration make it possible to suspect thyroid dysfunction even before clinical manifestations, which increases the value of correct and timely measurement of it. In the clinical practice, an endocrinologist often encounter the well-known phenomenon of macroprolactinemia; a much less common phenomenon is macrotyrotropinemia (macro-TSH). The presence of macro-TSH complexes can be suspected when the serum detects atypically high TSH values with reference values of FT4 without any signs of hypothyroidism. Since the phenomenon is based on an autoimmune mechanism, macro-TSH can often be detected in patients with autoimmune thyroiditis (AIT). This article presents clinical cases of patients with a combination of the macro-TSH phenomenon and primary hypothyroidism due to AIT.