Question

Describe the role of hormones secreted by thyroid glands.

Answer 1

The Thyroid gland helps in regulating the metabolic rate of the body. The pituitary gland and hypothalamus control the thyroid gland.The hypothalamus directs the pituitary to secrete TSH by secreting TRH or thyroid-releasing hormone and thus the cycle of hormone secretion starts.

Complete answer:
The thyroid-stimulating hormone or TSH is secreted by the pituitary gland and sends it to the thyroid gland. TSH informs the thyroid gland to secrete a specific amount of hormone. Thus, the TSH level in the blood depends on the need of the body.
Two hormones thyroxine and triiodothyronine are produced by the thyroid gland. These are referred to as T4 and T3 respectively. Twenty percent of thyroxine is produced by the thyroid gland and on the other hand, eighty percent of triiodothyronine is produced.
When T4 is secreted by the thyroid gland, the enzymes in the liver and kidneys transform it into thyroxine depending on the need of the body. The thyroid hormones help all the organs and cells of the body.

They control the way the muscles can contract.
They control the rate of the heartbeat.
They may raise or lower the body temperature.
They influence the rate at which the food moves in the digestive tract.
They control the rate at which the dead cells are replaced.
They help in weight management as they affect the rate of burning the calories in the body.

Note:
The good functioning of the thyroid gland depends on the iodine supply in the body.Tumors and diseases in the pituitary can affect the secretion of thyroid hormones.The cycle of secretion of hormones is known as the HPT or hypothalamic-pituitary-thyroid axis.