But the power of Follicular cells, also known as the C cells, are the cells that release and produce calcitonin inside our thyroid gland. Now, unlike these two hormones, calcitonin is a peptide hormone. It's a large peptide. And that basically means it's water soluble. It can easily dissolve and travel inside our blood, and it binds on to receptor proteins on the plasma membrane of the target cell. Now, in the case of T three and T four, their release is controlled by the hypothalamus and by the anterior pituitary gland.