An immunoglobulin G complexed form of thyroid-stimulating hormone (macro thyroid-stimulating hormone) is a cause of elevated serum thyroid-stimulating hormone concentration.

Background: Macrocomplexes can be the cause of elevated serum hormone concentrations and may cause diagnostic confusion. This is well recognized for prolactin and commonly screened for using polyethylene glycol (PEG) precipitation. The phenomenon and a suitable screening method is less familiar with respect to thyroid-stimulating hormone (TSH).