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?

A. Serum T4: In primary hypothyroidism, serum T4 levels are typically low because the thyroid is underactive. Therefore, an elevation of serum T4 would indicate hyperthyroidism not primary hypothyroidism. B. Serum T3: Serum T3 levels are usually low in primary hypothyroidism as well. T3 is the active thyroid hormone, and its production is reduced when the thyroid gland is not functioning properly. C. Thyroid stimulating hormone (TSH): In primary hypothyroidism, TSH levels are elevated. The pituitary gland produces more TSH to stimulate the thyroid gland to produce more thyroid hormones, but the thyroid is not responding effectively. D. Free T4: Free T4 refers to the unbound, active form of thyroxine. In primary hypothyroidism, the free T4 levels would be decreased because the thyroid gland is not producing sufficient amounts of this active hormone.