Your thyroid is a small, butterfly-shaped gland in the front of your neck. It makes hormones that control the way the body uses energy. These hormones affect nearly every organ in your body and control many of your body's most important functions. For example, they affect your breathing, heart rate, weight, digestion, and moods.

Thyroid tests check how well your thyroid is working. They are also used to diagnose and help find the cause of thyroid diseases such as hyperthyroidism and hypothyroidism. Thyroid tests include blood tests and imaging tests.

Blood tests for your thyroid include:

• TSH. It measures thyroid-stimulating hormone. This is usually the first test your healthcare provider will order.
• T3 and T4.They measure the level of the different thyroid hormones in your blood.
• Thyroid antibodies test. It measures certain thyroid antibodies (markers in the blood). This test may help diagnose autoimmune thyroid disorders.

Imaging tests include:

• CT scans
• Ultrasound
• Nuclear medicine tests, including:
  • Thyroid scan. It uses small amounts of radioactive material to create a picture of the thyroid, showing its size, shape, and position. It can help find the cause of hyperthyroidism and check for thyroid nodules (lumps in the thyroid).
  • Radioactive iodine uptake test, or thyroid uptake test. It checks how well your thyroid is working and can help find the cause of hyperthyroidism.

NIH: National Institute of Diabetes and Digestive and Kidney Diseases