Which of the following findings is most likely in a patient with symptomatic hypothyroidism?
Active uptake and concentration of iodide in the thyroid gland initiates the production of thyroid hormone. After organification, monoiodothyronine or diiodothyronine are coupled enzymatically by thyroid peroxidase to form either T3 or T4. These hormones are attached to thyroglobulin protein and stored as colloids in the gland. Thyrotropin, or thyroid-stimulating hormone (TSH), is produced in the anterior pituitary gland and its secretion is regulated by thyrotropin-releasing hormone produced in the hypothalamus. TSH is responsible both for the uptake of iodine and the proteolytic release of thyroid hormone. As thyroid function diminishes, serum thyrotropin concentrations increase. The combination of increased serum thyrotropin concentrations and normal free T4 and T3 concentrations is termed subclinical hypothyroidism or mild thyroid failure. As thyroid failure progresses, serum T4 concentrations decrease and the combination of increased thyrotropin concentrations and decreased T4 concentrations...
