Which laboratory tests are essential in diagnosing thyroid storm?

The diagnosis of thyroid storm, a severe and potentially life-threatening exacerbation of hyperthyroidism, hinges on measuring thyroid hormone levels. The essential laboratory tests for diagnosing this condition are free thyroxine (FT4), total triiodothyronine (T3), and thyroid-stimulating hormone (TSH).

In thyroid storm, there is typically an increase in FT4 and total T3 levels due to the excessive production of thyroid hormones. TSH levels are often suppressed in this context because the high levels of thyroid hormones exert negative feedback on the pituitary gland. Therefore, measuring these hormone levels is crucial for confirming the diagnosis of thyroid storm.

While other tests such as a complete blood count and metabolic panel, liver function tests, electrolytes, thyroid antibodies, and ultrasound imaging may provide useful information in the clinical management of hyperthyroid patients or in assessing complications, they are not specific or essential for diagnosing thyroid storm itself. The key indicators remain the thyroid hormone levels, as they directly reflect the state of thyroid activity and are critical for making an accurate diagnosis.