What are the recommended initial investigations for a patient suspected of having hyperthyroidism?

For a patient suspected of having hyperthyroidism, the initial investigations involve thyroid function tests (TFTs) ².

• For adults where secondary thyroid dysfunction (pituitary disease) is not suspected, consider measuring thyroid-stimulating hormone (TSH) alone ². If the TSH level is below the reference range, then measure free thyroxine (FT4) and free tri-iodothyronine (FT3) from the same sample ².
• For adults where secondary thyroid dysfunction (pituitary disease) is suspected, or for children and young people, consider measuring both TSH and FT4 initially ². If the TSH is below the reference range, measure FT3 in the same sample ².

It is important to note that testing for thyroid dysfunction should generally not be done during an acute illness, unless the acute illness itself is suspected to be due to thyroid dysfunction, as acute illness can affect test results ². Additionally, always ask patients about their biotin intake, as high consumption from dietary supplements can lead to falsely high or low test results ². If symptoms worsen or new symptoms develop, consider repeating the thyroid function tests, but no sooner than 6 weeks from the most recent test ².