Parafollicular cells, also known as C cells, are specialized cells located in the thyroid gland. They play a crucial role in regulating calcium levels in the body by producing the hormone calcitonin. This hormone helps lower blood calcium levels by inhibiting the activity of osteoclasts, the cells responsible for breaking down bone. These cells are found in the interstitial spaces between the thyroid follicles, which contain thyroid hormones like thyroxine (T4) and triiodothyronine (T3). Parafollicular cells respond to elevated calcium levels in the blood, releasing calcitonin to maintain calcium homeostasis and support overall bone health.