Which gland regulates metabolism in the body?

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

Answer: (C)

The gland that regulates metabolism is the thyroid. It releases thyroid hormones (T3 and T4) that set the body's metabolic rate—the speed at which cells convert nutrients into energy. These hormones ramp up enzyme activity and mitochondrial respiration, increasing heat production, heart rate, and overall energy use. This regulation happens through the hypothalamic-pituitary-thyroid axis: the hypothalamus signals the pituitary, which releases TSH to stimulate the thyroid to produce T3 and T4. When thyroid hormone levels rise, metabolism speeds up; when they fall, metabolism slows down. Other glands influence metabolism in different ways (adrenal hormones during stress, pancreatic hormones controlling blood glucose), but the thyroid directly determines the baseline metabolic pace.