Which hormone is secreted by the thyroid gland to regulate metabolism?

The hormone that is secreted by the thyroid gland to regulate metabolism is thyroxine, commonly known as T4. Thyroxine plays a crucial role in maintaining the body's metabolic rate by influencing the speed at which cells perform their functions. This hormone stimulates the utilization of oxygen and the production of heat, which ultimately impacts the body's energy expenditure.

Thyroxine is essential for normal growth and development, as well as for the regulation of various metabolic processes, including carbohydrate, protein, and fat metabolism. A deficiency or excess of T4 can lead to significant health issues, such as hypothyroidism or hyperthyroidism, respectively, both of which cause alterations in metabolic rates.

In contrast, cortisol is a steroid hormone produced by the adrenal glands, primarily involved in stress response and metabolism of carbohydrates, fats, and proteins. Glucagon is produced by the pancreas and is responsible for increasing blood glucose levels, primarily working in opposition to insulin. Parathyroid hormone (PTH), secreted by the parathyroid glands, regulates calcium levels in the blood. These hormones have specific functions related to metabolism and homeostasis but are not secreted by the thyroid gland.