The thyroid gland is a bilobed organ situated anterior to the pharynx. This gland comprises two principal types of cells, which are responsible for secreting thyroid hormones and calcitonin.

Thyroid hormones have functions in thermogenesis and nutrient metabolism. Disorders associated with the secretion or response of this hormone will generally affect basal metabolism and energy levels.

Although calcitonin is responsible for decreasing blood calcium levels, a loss of calcitonin, as in a thyroidectomy, has not yet been implicated as a cause of any disease state.