hyperthyroidism can be suspected in patients with: tremors. excessive sweating. smooth velvety skin. fine hair. a rapid heart rate. an enlarged thyroid gland. there may be puffiness around the eyes and a characteristic stare because of the elevation of the upper eyelids. advanced symptoms are easily detected but early symptoms especially in the elderly may be quite inconspicuous. in all cases a blood test is needed to confirm the diagnosis. the blood levels of thyroid hormones can be measured directly and usually are elevated with hyperthyroidism. however the main tool for detection of hyperthyroidism is measurement of the blood thyroid-stimulating hormone (tsh) level. tsh is secreted by the pituitary gland. if an excess amount of thyroid hormone is present tsh is "down-regulated" and the level of tsh falls in an attempt to reduce production of thyroid hormone. thus the measurement of tsh should result in low or undetectable levels in cases of hyperthyroidism. however there is one exception. if the excessive amount of thyroid hormone is due to a tsh-secreting pituitary tumor then the levels of tsh will be abnormally high. this uncommon disease is known as "secondary hyperthyroidism. " although the blood tests mentioned previously can confirm the presence of excessive thyroid hormone they do not point to a specific cause. if there is obvious involvement of the eyes a diagnosis of graves' disease is almost certain. a combination of antibody screening (for graves' disease) and a thyroid scan using radioactively labelled iodine (which concentrates in the thyroid gland) can help diagnose the underlying thyroid disease. these studies are chosen on a case-by-case basis.
how is hyperthyroidism diagnosed?