Thyroid Nuclear Medicine Tests (Thyroid Scan and Uptake)

What Is It?

There are two types of thyroid nuclear medicine tests. Both assess the health of your thyroid, a gland in your neck. The first type, a thyroid scan, produces a picture of the gland. It can spot lumps or inflammation, or to investigate the cause of an overactive thyroid. The second type, a radioactive iodine uptake test, is performed to see if your thyroid is functioning normally and to determine why thyroid hormone levels may be elevated. For both types of test, a small amount of a weakly radioactive substance, known as a radionuclide, is either injected into a vein or given to you as a pill.

What It's Used For

A thyroid scan is usually ordered when a physical examination or laboratory finding suggests that the thyroid is enlarged or has a lump (called a thyroid nodule). If laboratory tests show an overactive thyroid, a radioactive iodine uptake test may be ordered at the same time to evaluate thyroid function.

Preparation

If there is any chance that you are pregnant, or if you are breast-feeding, let your doctor know: radionuclides could harm a developing fetus or your nursing baby. Your doctor has other ways of diagnosing the problem, such as ordering additional blood tests or a thyroid ultrasound.

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