An adult patient with subclinical hyperthyroidism has routine lab results. What finding would most likely be observed in their lab values?

Rationale: A. This pattern is characteristic of primary hypothyroidism, where the thyroid gland underproduces T4, prompting the pituitary to release more TSH. This does not reflect subclinical hyperthyroidism. B. Elevated TSH typically indicates hypothyroidism, not hyperthyroidism. Subclinical hyperthyroidism is associated with suppressed TSH, not elevated levels. C. Normal TSH levels suggest euthyroid status, meaning the thyroid is functioning within the normal range. In subclinical hyperthyroidism, TSH is typically below normal, even if T4 and T3 are within reference ranges. D. Subclinical hyperthyroidism is defined by a suppressed or low TSH with normal free T4 and T3 levels. The patient may be asymptomatic or have mild symptoms, but the laboratory finding of low TSH is the hallmark. Identifying this pattern is important because prolonged subclinical hyperthyroidism can increase the risk of atrial fibrillation, bone loss, and progression to overt hyperthyroidism.