A nurse in a clinic is reviewing the laboratory values of a client who has primary hypothyroidism. The nurse should anticipate an elevation of which of the following laboratory values?

Rationale: A. Free T4: In primary hypothyroidism, free T4 levels are typically decreased because the thyroid gland is underactive and not producing sufficient thyroid hormone. An elevation of free T4 would not be expected in this condition. B. Serum T4: Total serum T4 is also decreased in primary hypothyroidism for the same reason as free T4. The thyroid gland cannot produce enough hormone, so serum T4 levels fall rather than rise. C. Thyroid stimulating hormone (TSH): In primary hypothyroidism, the thyroid gland fails to produce adequate thyroid hormones. The pituitary gland responds by increasing secretion of TSH in an attempt to stimulate the thyroid, making elevated TSH the expected finding. D. Serum T3: Serum T3 levels are usually low or normal in hypothyroidism but not elevated. Because T3 is converted from T4, when T4 production drops, T3 levels also generally decrease over time.