Which gland primarily regulates basal metabolic rate?

Which gland primarily regulates basal metabolic rate?

• A. Pancreas
• B. Thyroid gland
• C. Adrenal cortex
• D. Adrenal medulla

Answer: (B)

Basal metabolic rate is largely set by thyroid hormones, T3 and T4, which act on nearly every cell to boost energy use. They ramp up cellular metabolism, increase heat production, and enhance the activity of metabolic enzymes and mitochondria, so the body's resting energy expenditure sits at a higher level when thyroid hormone levels are high. This regulation is controlled by the hypothalamic-pituitary-th thyroid axis: TRH from the hypothalamus stimulates TSH from the pituitary, which then prompts the thyroid to release T3/T4, with negative feedback tuning the system. Clinically, overactivity raises BMR (weight loss, heat intolerance) and underactivity lowers BMR (weight gain, cold intolerance). Other glands influence metabolism in different ways or only under stress, but the thyroid mainly governs the baseline metabolic rate.