What initial test should be ordered for a patient with symptoms suggesting hyperthyroidism?

In cases where a patient exhibits symptoms of hyperthyroidism, the most appropriate initial test to order is a thyroid-stimulating hormone (TSH) level. This test is crucial because it helps assess the patient's thyroid function by measuring the amount of TSH in the blood, which indicates how well the thyroid is working. TSH is produced by the pituitary gland, and its levels can be suppressed when there is an excess of thyroid hormones (as seen in hyperthyroidism).

By evaluating TSH, healthcare providers can determine if further testing is necessary, such as measuring free thyroxine (T4) and triiodothyronine (T3) levels, to clarify the diagnosis and assess the severity of hyperthyroidism. This sequential approach is more diagnostic and effective compared to starting with other tests.

While a blood chemistry panel, liver function studies, and an electrocardiogram can be valuable in clinical assessments, they do not directly address thyroid function and are not the primary tests indicated for evaluating hyperthyroidism. These tests might be used for evaluating symptoms less specific to thyroid issues or for assessing complications and comorbidities arising from hyperthyroidism, but they are not the first-line evaluation tool for thyroid-related symptoms.