Thyroid function test interpretation for general paediatricians.

A thyroid function test (TFT) is a common investigation, often undertaken by general paediatricians and general practitioners. TFT involves the measurement of serum free thyroxine (fT4) and thyroid stimulating hormone (TSH) to guide the diagnosis and management of hypothyroidism and hyperthyroidism, requiring treatment with medications such as levothyroxine (LT4) and carbimazole. Thyroid hormones play a crucial role in early life neurodevelopment; therefore, the correct interpretation of TFT is required to optimise treatment outcomes. TFT needs to be contextualised to influencing factors such as intercurrent illness, diet, presence of obesity, assay interference and non-adherence to treatment.