Fig 1.

Schematic representation of different patterns of thyroid function tests and their causes. ATDs = antithyroid drugs; FDH = familial dysalbuminaemic hyperthyroxinaemia; FT3 = free triiodothyronine; FT4 = free thyroxine; NTI = non-thyroidal illness; TH = thyroid hormone; TKIs = tyrosine kinase inhibitors; TSH = thyroid-stimulating hormone (thyrotropin). *signifies that TSH can be either fully suppressed (eg as seen in classical primary hyperthyroidism) or partially suppressed (ie measureable, but below the lower limit of normal).