Common mistakes around TSH Check

Common mistakes around TSH testing include improper timing, medication interference, and overreliance on a single value. TSH follows a circadian rhythm, peaking at night and dipping in the afternoon; morning sampling (before 10 a.m.) is recommended. High-dose biotin (common in supplements) can falsely lower TSH, as can corticosteroids, dopamine agonists, and opioids. Conversely, lithium and amiodarone may elevate TSH. A single TSH result is insufficient for diagnosis – free T3, free T4, and antibodies are needed when central hypothyroidism or pituitary disease is suspected. Reference ranges vary by lab and population; a 'normal' TSH does not rule out dysfunction. In pregnancy, trimester-specific ranges apply. In summary, TSH is a useful screening tool but not a standalone diagnostic. Interpretation must consider medication, timing, and clinical context.