Thyroid level tests, including thyroid-stimulating hormone (TSH) and free T4, help diagnose underactive or overactive thyroid. Doctors may also check free T3, calcitonin, thyroglobulin, or thyroid ...

Hyperthyroidism, also sometimes referred to as overactive thyroid, is a health condition caused by an excess level of thyroid hormone in the body. Although any individual may be affected, it is far ...