Thyroid Stim Immunoglobulin

This test detects thyroid-stimulating immunoglobulins (TSI), antibodies that mimic thyroid-stimulating hormone and can cause excessive thyroid activity. It's ordered when Graves' disease is suspected based on symptoms like fatigue, heart palpitations, heat intolerance, or unexplained weight loss, or to monitor disease status in known cases.

Undiagnosed Graves' disease can significantly impair athletic performance through uncontrolled metabolism, reduced exercise tolerance, cardiac arrhythmias, and prolonged recovery. TSI testing may be relevant for athletes experiencing unexplained fatigue, elevated resting heart rate, or performance decline despite adequate training, though this is not a routine performance marker for healthy individuals.