Which gland is responsible for regulating metabolic rate?

• A. Pituitary gland
• B. Parathyroid
• C. Adrenal
• D. Thyroid gland

Answer: (D)

Metabolic rate at rest is set mainly by thyroid hormones produced by the thyroid gland. The hormones T3 and T4 ramp up cellular activity across tissues by increasing the production of metabolic enzymes, boosting mitochondrial function, and raising heat production. This combination raises oxygen use and energy expenditure, defining the basal metabolic rate. The pituitary gland does regulate thyroid activity by releasing TSH, but the direct regulator of metabolic rate is the thyroid gland itself through its hormone output. The parathyroid glands control calcium balance, not metabolism, while the adrenal glands influence metabolism mainly in response to stress.