Tucked between the hollow balls of your thyroid are a few special cells. They are C cells, and they help keep the calcium in your blood from getting too high.
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Your thyroid gland in your neck is full of tiny hollow balls called follicles. Parafollicular cells (say pair-uh-fuh-LIK-yoo-lar) sit next to and between these balls. "Para" means "beside".
They are also called C cells. They are bigger and paler than the cells around them, and there are only a few of them.
C cells are a different kind of cell from the rest of the thyroid. When a baby is growing, they start out somewhere else and move into the thyroid!
Your blood needs just the right amount of calcium. Calcium helps your muscles, nerves, and heart work, and it builds strong bones.
When there is too much calcium in the blood, C cells send out a hormone called calcitonin (say kal-sih-TOE-nin). It helps your bones hold on to their calcium.
Scientists are still learning how important calcitonin is for people. Other cells, in the parathyroid glands, do most of the calcium work.
Scroll up to the 3D model and press Send calcitonin.