What organ is responsible for regulating metabolism?

What organ is responsible for regulating metabolism? The thyroid gland.

The thyroid is an endocrine gland in the neck that produces the hormones triiodothyronine, or T3, and thyroxine, or T4. These hormones influence the metabolic rate of nearly every tissue in the body.

Thyroid hormones increase basal metabolic rate and affect how cells use carbohydrates, fats, and proteins. They also influence heat production, heart activity, digestion, growth, and development.

The hypothalamus does participate in the wider hypothalamic–pituitary–thyroid axis by releasing thyrotropin-releasing hormone. That signal ultimately prompts the thyroid to produce T3 and T4, but the thyroid is the organ most directly associated with metabolic regulation.