ALFRED PASIEKA / SCIENCE PHOTO LIBRARY ALFRED PASIEKA / SCIENCE PHOTO LIBRARY
Thyroid gland. Coloured scintigram of a healthy thyroid gland. This two-lobed endocrine gland is found in the neck, where it lies on top of the trachea (windpipe). It is responsible for the production of thyroxine (T4), tri-iodothyronine (T3) and calcitonin, hormones that control the body's metabolism and energy levels. They are vital for normal mental and physical development in children. Using the radioactive tracer iodine- 123, a scintigram shows the activity of the thyroid gland, from red (most active) through yellow and green to blue (least active).
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