What is the role of thyroid function tests in the assessment of patients with unexplained symptoms?

Thyroid function tests play a key role in the assessment of patients presenting with unexplained symptoms by helping to identify or exclude thyroid dysfunction as a potential cause. They should be considered when there is clinical suspicion of thyroid disease, although a single symptom alone may not be indicative of thyroid dysfunction.

Tests for thyroid dysfunction are particularly recommended for adults, children, and young people presenting with unexplained symptoms such as depression, anxiety, abnormal growth, or changes in behaviour or school performance.

Additionally, thyroid function tests are advised in patients with type 1 diabetes, other autoimmune diseases, or new-onset atrial fibrillation, as these conditions are associated with thyroid disease.

In menopausal women, thyroid dysfunction symptoms may mimic menopausal symptoms, so testing can help differentiate the cause.

Typically, thyroid function testing involves measuring thyroid stimulating hormone (TSH) first; if TSH is abnormal, free thyroxine (FT4) and free triiodothyronine (FT3) are measured in the same sample to clarify the thyroid status.