Which hormone produced by the thyroid regulates metabolism?

• A. Epinephrine
• B. Glucagon
• C. Calcitonin
• D. Thyroxine

Answer: (D)

Thyroid hormones set the body's baseline energy use. The hormone produced by the thyroid that regulates metabolism is thyroxine (T4), which is released by the thyroid and is often converted to the more active form, T3, in target tissues. T3 and T4 increase the rate of cellular metabolism, raise the basal metabolic rate, boost heat production, and influence carbohydrate, fat, and protein metabolism.

Other hormones listed come from different glands and have different primary roles: epinephrine from the adrenal medulla drives rapid energy mobilization during stress, glucagon from the pancreas raises blood glucose, and calcitonin from the thyroid mainly helps regulate calcium levels in the blood.