Hormone of thyroid gland
Thyroid hormone
Follicular cells of thyroid gland secretes two iodine containing hormone.
Iodine is essential for formation of thyroid hormone.
1. T3 Tri-iodothyronine (containing three iodine atoms)
2. T4 Thyroxine or Tetraiodothyronine ( containing of four iodine atoms)
3. Calcitonin
The release of T3 and T4 into blood is stimulated by thyroid stimulating hormone (TSH) from anterior pituitary.
Thyroid gland also produces and releases hormone calcitonin, which contribute regulation of blood calcium levels.
Calcitonin decreases concentration of calcium in blood.
Most calcium removed from blood is stored in bones.
Function of Thyroid Hormone (T3 and T4)
1. Primary effect of TH is to increase body's metabolic rate.
2. Increasing basal metabolic rate and heat production.
3. Regulating metabolism of;
Carbohydrates (CHO)
Proteins
Fats
4. Thyroid hormone promote alertness, bone growth and remodeling and development of;
Skin, Hair, Nails, Teeth, Fetal nervous system, muscular system, skeletal development.
5. It also stimulates pituitary gland to secrete growth hormone.
6. It promotes normal functioning of heart.
Promotes normal gastrointestinal motility and increase secretion of digestive juice.
7. Function of calcitonin
It contribute to regulation of blood calcium.
It act on bone cells and kidney to reduce blood calcium levels when they are raised.
Its most important effect is to lower blood Ca2+ levels.
It promotes storages of calcium in bones and inhibits reabsorption of calcium by renal tubules.
It's effect is opposite to that of parathyroid glands.
Release of calcitonin is stimulated by increase in blood calcium levels.
Calcitonin can also be used therapeutically for treatment of Hypercalcemia or osteoporosis.
Parathyroid Gland
Parathyroid gland composed of two major cells;
1. Chief cells (produce parathyroid hormone)
2. Oxyphils cells
Parathyroid hormone (PTH) or Parathormone
Parathyroid gland secrete parathyroid hormone (PTH).
Secretion is regulated by blood calcium level.
When they fall, secretion of PTH is increases and vice-versa.
Vitamin D is required for absorption of calcium from digested food.
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