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?

A. "This test measures the absorption of iodine and how it relates to the thyroid gland." TSH testing does not assess iodine absorption; it measures pituitary stimulation of the thyroid. B. "This test determines whether your thyroid gland is overactive, appropriately active, or underactive." TSH reflects pituitary signaling to the thyroid; elevated TSH suggests hypothyroidism, while low TSH suggests hyperthyroidism. C. "This test detects antithyroid antibodies in your blood." Antithyroid antibodies are tested in conditions like Hashimoto’s or Graves’ disease, not TSH measurement. D. "This test measures the amount of thyroid hormone that attaches to a protein in your blood." This describes total thyroid hormone levels, not TSH.