A thyroid ultrasound is a safe, painless procedure that uses sound waves to examine the thyroid gland. It can be used to help diagnose a wide range of medical conditions affecting the thyroid gland, including benign thyroid nodules and possible thyroid cancers. Clinicians can use thyroid ultrasound to evaluate several different medical conditions that affect the thyroid gland, an endocrine gland in your neck. The thyroid hormone produced by the gland affects many important physiological functions, including heart rate, body temperature, and overall metabolism.