In overt hyperthyroidism, serum levels of free T4 and triiodothyronine (T3) or levels of T3 alone are elevated, and serum thyrotropin (TSH) levels are suppressed. In subclinical hyperthyroidism, levels of free T4 and T3 are normal, thyrotropin levels are suppressed, and thyroid hormone levels are usually in the middle to upper range of normal. Continue reading →