A nurse is talking with a client whose thyroid-stimulating hormone (TSH) level will be measured. Which of the following statements by the nurse explains the purpose of this test?

Rationale: A. This test detects antithyroid antibodies in your blood: Antithyroid antibody testing is used to diagnose autoimmune thyroid disorders such as Hashimoto’s thyroiditis or Graves’ disease. It does not measure thyroid gland activity directly like TSH does. B. This test determines whether your thyroid gland is overactive, appropriately active, or underactive: TSH is produced by the pituitary gland and regulates thyroid hormone secretion. Measuring TSH helps identify thyroid function status, indicating hyperthyroidism when low, hypothyroidism when high, or euthyroid when within normal range. C. This test measures the absorption of iodine and how it relates to the thyroid gland: An iodine uptake scan measures the thyroid gland’s ability to take in iodine, which is essential for hormone production. This is a separate diagnostic test and not the purpose of a TSH level. D. This test measures the amount of thyroid hormone that attaches to a protein in your blood: This refers to thyroid-binding globulin (TBG), which assesses how much thyroid hormone is bound to serum proteins. It does not indicate thyroid gland activity as directly as TSH testing does.