Thyroid function tests are among the most commonly requested laboratory investigations in primary care — yet a small but important subgroup of results can appear discordant or inconsistent with the clinical picture.
Using a case study of a patient with markedly elevated TSH and normal FT4, this course revisits hypothalamic-pituitary-thyroid (HPT) axis physiology and explains the inverse log-linear relationship between TSH and FT4. It explores biological variation, medication effects, poor compliance with thyroxine therapy, non-thyroidal illness, and assay interference.
-
Understand the physiology of the HPT axis and the inverse relationship between TSH and FT4
-
Understand how intermittent thyroxine compliance affects results
-
Recognise normal biological variation in TSH levels
-
Recognise potential assay interferences in immunoassays
-
Identify common causes of raised TSH with normal FT4
-
Apply a structured approach to managing discordant thyroid function tests
