HCC Ybor Campus HCC SouthShore Campus HCC Plant City Campus HCC District Administrative Offices HCC Dale Mabry Campus HCC Brandon Campus

     (1) "thyroid_metabolic hormones" and

     (2) calcitonin, which is also known as thyrocalcitonin.

The "thyroid metabolic hormones" are two separate substances

     (1) T3, known as triiodothyronine and

     (2) T4, known as thyroxine or tetraiodothyronine.  

Both T3 and T4 help regulate metabolism. Calcitonin decreases blood calcium levels by stimulating calcium deposits in bones.

The thyroid is composed of structures called follicles, which contain colloid. Colloid contains thyroglobin. This substance the precursor for T3 and T4 . The cells that make up the follicle border are called follicular cells. Scattered among, but external to, the follicles are parafollicular (C-cells) cells. These cells produce calcitonin.

Parathyroid glands are located on the posterior side of the thyroid gland. There are usually two oval parathyroids on each lobe of the thyroid, but sometimes there are more.

The parathyroid (chief) cells are the most numerous cells in the parathyroid. They produce parathyroid_hormone or PTH, which regulates the removal of calcium from bones to regain calcium homeostasis in the bloodstream. Human parathyroids (but not the parathyroids of other mammals) have additional cells, which are called oxyphil_cells. The function of oxyphil cells is still unknown.

parathyroid thyroid follicle filled with colloid follicle filled with colloid follicle filled with colloid follicle filled with colloid parafollicular (C cells) parafollicular (C cells) parafollicular (C cells) follicle filled with colloid follicle filled with colloid follicle filled with colloid parafollicular (C cells) parafollicular (C cells) parafollicular (C cells) parafollicular (C cells) follicle filled with colloid follicle filled with colloid follicle filled with colloid parafollicular (C cells) parafollicular (C cells) follicle filled with colloid