Lecture (5-6) Hormones SCBC 311 PDF

Lecture (5-6) Hormones SCBC 311 1 Prof. Maha Alkhalaf  Overview of the parathyroid gland The parathyroid glands are small endocrine glands in the neck that produce parathyroid hormones (PTH...

Lecture (5-6) Hormones SCBC 311 1 Prof. Maha Alkhalaf  Overview of the parathyroid gland The parathyroid glands are small endocrine glands in the neck that produce parathyroid hormones (PTH). Humans usually have four tiny parathyroid glands, which are usually located on the back of the thyroid gland, Each gland is about the size of a grain of rice (weighs approximately 30 milligrams and is 3-4 millimeters in diameter). Parathyroid glands control the amount of calcium in the blood and within the bones. 2 Prof. Maha Alkhalaf  Parahyroid gland Hormones Parathyroid hormone (PTH), parathormone or parathyrin, is essential for life, is secreted by the chief cells of the parathyroid gland as a polypeptide containing 84 amino acids. PTH half-life is approximately 4 minutes. It has a molecular mass of 9.4 kDa. The physiological activity of the hormone on both skeletal and renal tissues. PTH is key to regulating and maintaining a balance of your body's levels of two minerals — calcium and phosphorus. Prof. Maha Alkhalaf 3  4 Prof. Maha Alkhalaf  Regulation of PTH secretion The parathyroid cell is unusual in that decreasing concentrations of calcium stimulate secretion of PTH, and increasing concentrations of calcium inhibit secretion of PTH. Thus, this cell, which is responsible for the critical maintenance of ionized blood calcium levels, is, in turn, regulated by calcium itself Prof. Maha Alkhalaf 5  Endocrine regulation of calcium and phosphate metabolism Hormonal regulation of Ca: PTH Vitamin D Calcitonin Major regulatory organs: Bone- Kidney- intestine 6 Prof. Maha Alkhalaf  Function of the Regulates the proportion of calcium and phosphorus in the blood and make it stable and maintain the parathyroid proper balance between calcium and phosphorus in the body and maintain the normal level of each in the hormone (PTH) blood as a result of its impact on the tissues of the target Major target organ: Bone: Increase bone resorption by stimulating osteoclast inhibiting osteoblast (movement or mobilization of calcium from bones to blood) Kidney: increased calcium resorption increased phosphorus excretion Decreased calcium excreation Intestinal tract (indirect effect of vit D): increased calcium absorption from small intestine 7 Prof. Maha Alkhalaf  PTH acts to increase the concentration of calcium in the blood by: 2-promotes calcium 1-Stimulating osteoclast conservation 3-PTH decrease the to break down bone and (reabsorption) by the urinary excretion of release calcium. kidney [Reduction of renal calcium. Ca excretion]. PTH affects the 5-PTH also increases 4-PTH increase the perception of well being gastrointestinal calcium urinary excretion of and absence of PTH can absorption by activating phosphate. be associated with feeling vitamin D. of fatigue and anxiety. 8 Prof. Maha Alkhalaf  What does the parathyroid gland control? As the blood filters through the parathyroid glands, they detect the amount of calcium present in the blood and react by making more or less parathyroid hormone (PTH). When the calcium level in the blood is too low, the cells of the parathyroids sense it and make more parathyroid hormone. 9 Prof. Maha Alkhalaf  10 Prof. Maha Alkhalaf  11 Prof. Maha Alkhalaf  Disorder of Parathyroid Gland Hyperparathyroidism It is a condition resulting from excessive production of PTH. It is characterized by elevated serum ionized calcium and PTH and decreased serum phosphate levels. Symptoms and signs: include extensive bone resorption, kidney stones formation and frequent urinary tract infections. 12 Prof. Maha Alkhalaf  Two types of hyperparathyroidism exist: Primary hyperparathyroidism an enlargement of one or more of the parathyroid glands causes overproduction of the hormone, resulting in high levels of calcium in the blood (hypercalcemia), which can cause a variety of health problems. Surgery is the most common treatment for primary hyperparathyroidism. Secondary hyperparathyroidism occurs as a result of another disease that initially causes low levels of calcium in the body and over time, increased parathyroid hormone levels occur. 13 Prof. Maha Alkhalaf  2. Hypoparathyroidism It is a condition resulting from insufficient amount of PTH. It is characterized by decreased serum ionized calcium and elevated serum phosphate. Symptoms include neuromuscular irritability, tetany and in sever cases tetanic paralysis of respiratory muscles leading to death. Supplements to normalize your calcium and phosphorus levels treat the condition. Depending on the cause of your hypoparathyroidism, you'll likely need to take supplements for life. 14 Prof. Maha Alkhalaf  What is the difference between thyroid and parathyroid glands? The thyroid gland uses iodine from food to make two thyroid hormones (T3 and T4) that regulate the way the body uses energy. The parathyroid glands are four tiny glands located behind the thyroid gland. The parathyroid glands produce a substance (parathyroid hormone) that helps control the amount of calcium in the blood. 15 Prof. Maha Alkhalaf  What regulates parathyroid hormone? Parathyroid hormone (PTH) has a very powerful influence on the cells of your bones by causing them to release their calcium into the bloodstream. PTH regulates how much calcium is absorbed from your diet, how much calcium is excreted by your kidneys, and how much calcium is stored in your bones. 16 Prof. Maha Alkhalaf  How PTH The parathyroid hormone (PTH), secreted by regulate the parathyroid glands, is responsible for regulating blood calcium levels; it is released whenever blood calcium levels are calcium low. PTH increases blood calcium levels by level in the stimulating osteoclasts, which break down bone to release calcium into body? the blood stream. 17 Prof. Maha Alkhalaf  The quantity of calcium ions excreted in the How is urine per day is partially under the influence of the plasma calcium parathyroid hormone (PTH) level - high levels of PTH decreasing the excreted rate of calcium ion excretion, and from the low levels increasing it. body? 18 Prof. Maha Alkhalaf  The amount of phosphate in the blood affects the level of calcium in the blood. How does calcium and Calcium and phosphate in the body react in opposite ways: as blood calcium levels phosphate work rise, phosphate levels fall. together in the body? A hormone called parathyroid hormone (PTH) regulates the levels of calcium and phosphorus in your blood 19 Prof. Maha Alkhalaf