Thyroid adenoma. Coloured gamma scan of a hot nodule" (red and white, right) pinpointing adenoma in the thyroid gland. Outlined in blue are the two lobes of the thyroid gland, an endocrine gland in the neck that produces hormones controlling the body's metabolism. The condition seen here, called toxic solitary adenoma, is caused by a benign tumour in the gland that produces excessive quantities of thyroid hormones, leading to hyperthyroidism. The image is made by injecting the patient with radioactive technetium, which concentrates in active parts of the thyroid gland, and then scanning the area with a gamma camera which detects radioactivity."