The illustration shows the thyroid with both of its laps and the connecting isthmus. The thyroid, also thyroidal gland, produces hormones that impact growth and metabolism. The parafollicular cells inside the basal membrane produce calcitonin which sinks the blood calcium levels. Furthermore, the thyroid stores and releases triiodothyronine (T3) and thyroxine (T4). They control carbon, lipid and protein metabolism, physical and mental development and water balance. It is controlled via a negative feedback mechanism between thyroid, hypophysis and hypothalamus.
