hyperthyroidism can be suspected in patients with tremors; excessive sweating; smooth velvety skin; fine hair; a rapid heart rate; and an enlarged thyroid gland. there may be puffiness around the eyes and a characteristic stare due to 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 are usually elevated with this disease. however the main tool for detection of hyperthyroidism is measurement of the blood thyroid stimulating hormone 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 control thyroid hormone production. 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 actually due to a tsh-secreting pituitary tumor then the levels are abnormally high. this uncommon disease is known as "secondary hyperthyroidism. "
how is hyperthyroidism diagnosed?