To diagnose hyperthyroidism your doctor may do the following:
If blood tests indicate hyperthyroidism, your doctor may ask for one of the following tests to help determine why your thyroid is overactive:
Radioactive iodine uptake test in which you are asked to orally ingest radioactive iodine. The iodine collects in your thyroid gland and at fixed intervals the amount of iodine used up by the gland is measured. High uptake of iodine indicates increased production of thyroxin by the thyroid gland.
Thyroid scan in which a special camera and radioactive isotope, injected in your vein, is used to produce images of your thyroid to be studied by the doctor.