Endocrine- Parathyroid PDF

Endocrine system Presented by: Dr. Yasmine Gamal Sabry Lecturer in the physiology department, faculty of medicine, Ain Shams university Faculty of physical therapy 1  Parathyroid Gland The parathyroid gl...

Endocrine system Presented by: Dr. Yasmine Gamal Sabry Lecturer in the physiology department, faculty of medicine, Ain Shams university Faculty of physical therapy 1  Parathyroid Gland The parathyroid glands are usually four small glands found on the posterior aspect (back) of the thyroid gland. They contain Chief cells that secrete Parathyroid Hormone (PTH). The main function of the PTH is regulation of the Ca+2 concentration in the ECF hence it is ESSENTIAL FOR LIFE. 2  PTH acts to Increase the plasma Calcium level and Decreases the plasma Phosphate level by its action on 3 target organs: 1-Skeleton: 2.Kidneys: 3. Intestine: Faculty of physical therapy 3  1-Skeleton: - PTH acts directly on bone to increase bone resorption and mobilize ionic calcium and phosphates to the blood. A)Immediate effect: - This effect begins within min &continues for hrs. PTH stimulates membrane bound Ca2+ pumps The Ca2+ (soluble, non-crystallized, labile Ca+2 pool) is transferred from bone fluid into plasma. Faculty of physical therapy 4 B) Delayed (chronic) effect: This takes days to weeks. PTH increases the number and activity of osteoclasts → which break down the Calcium crystals (insoluble, crystallized, stable Ca2+ pool) leading to localized dissolution of bone and release of Ca2+ into plasma (= osteoclast activation). Faculty of physical therapy 5  2.Kidneys: Plasma PTH directly stimulates reabsorption of calcium and magnesium and excretion of phosphate in the kidney. PTH also increases the formation of (active vitamin D3 = calcitriol). Urine Faculty of physical therapy 6 3. Intestine: PTH increases absorption of calcium by intestinal tract. - This action of PTH on intestine is: INDIRECT via vitamin D3 PTH increases the formation of calcitriol (vitamin D3) by kidney. Vitamin D3 in turn increases calcium absorption from intestine (through ↑ production of calcium binding proteins in intestinal mucosa called calbindin D ). Faculty of physical therapy 7 Faculty of physical therapy 8  Regulation of PTH - PTH is mainly regulated BY BLOOD CALCIUM LEVELS, not by any other gland. - The key to this regulation is a cell membrane Ca2+ sensing receptor on parathyroid glands and many tissues. - Circulating ionized calcium acts directly on the parathyroid glands in a negative feedback fashion to regulate the secretion of PTH. When PTH secretion is Ca2+ is deposited plasma Ca2+ level is high inhibited in bones. When PTH secretion Ca2+ resorption plasma from bones. Ca2+ is low is increased. Faculty of physical therapy 9  PTH is increased by ↓ Ionized plasma ↓ Plasma ↑ Plasma ↓ vit D3 calcium Mg2+ level. PO4 level. level. - Normally the plasma phosphorus concentration is inversely related to calcium concentration; their product is constant and is called the solubility product. [Ca2+] X [PO4-3] must remain constant. Faculty of physical therapy 10  Abnormalities of Parathyroid H. secretion Because calcium is essential for life so precise control of ionic calcium levels in body fluids is absolutely critical (8.5-10.5 mg/dl). Hyperfunction Hypofunction Hypercalcemia Hypo- calcemic Tetany Faculty of physical therapy 11 I- Hyperparathyroidism Faculty of physical therapy 12 ❖ Manifestations of primary hyperparathyroidism: - It is a disease of bones, stones and abdominal groans. - It is characterized by hypercalcemia and hypophosphatemia. 1- The bones soften and deform as their mineral salts are replaced by fibrous connective tissue. →Multiple bone cysts are present (Osteitis fibrosa cystica). →Thus the bone is subjected to spontaneous fractures & deformities. Faculty of physical therapy 13 ❖ Manifestations of primary hyperparathyroidism: 2- Formation of renal stones because of excess calcium salts being filtered through the kidneys →Leading to renal colic and hematuria. →Deposition of Ca2+ salts within kidney tissue → leading to renal failure. 3- Hypercalcemia decreases neuromuscular excitability which can be manifested by skeletal muscle weakness, decreased alertness, and poor memory. Faculty of physical therapy 14 ❖ Manifestations of primary hyperparathyroidism: 4- Gastrointestinal disorders e.g. peptic ulcer (as prolonged hypercalcemia has stimulatory effect on gastric acid secretion), and acute pancreatitis. - Nausea, vomiting and constipation (due to decreased intestinal motility) may occur (Abdominal Groans ). 5- Cardiac arrhythmias Treatment - Surgical removal of the tumor in primary hyperparathyroidism. - Treatment of the cause in secondary hyperparathyroidism. Faculty of physical therapy 15  II- Hypoparathyroidism Cause: The most common cause is accidental removal or injury of parathyroid glands (3 glands at least) during thyroid surgery (thyroidectomy) leading to hypo- calcemic tetany. Hypoparathyroidism is characterized by hypocalcemia and hyperphosphatemia. Complete absence of PTH leads to death while relative deficiency is manifested by tetany. Tetany: A state of spastic contraction of the skeletal muscle caused by increase neuromuscular excitability due to decreased ionized plasma Calcium level. Faculty of physical therapy 16 Causes of hypocalcemia: 1) Hypoparathyroidism. 2) Renal failure. 3) Alkalaemia (decrease ionized Ca2+). 4) Vitamin D deficiency. Faculty of physical therapy 17  Symptoms Manifest tetany Latent tetany Appear during rest when When the blood Ca++ level the blood Ca2+ level is from 7–8.5 mg%. decreases below 7 mg%. Tetanic contractions are Muscular twitches and absent at rest but appear attacks of tonic & colonic in certain situations contractions leading to (stress, hyperventilation, generalized convulsions pregnancy). (suffocation). Latent tetany could In between attacks become manifest by muscles are stiff showing Provocative tests. carpopedal spasm. Faculty of physical therapy 18 ❖ Provocative tests for latent tetany: Trousseau’s sign: - Occlusion of circulation of forearm by sphygmomanometer for few minutes causes ischemia of peripheral nerves resulting in flexion of wrist and thumb with extension of fingers. Chvostek’s sign: - Tapping over the facial nerve at angle of the jaw causes quick contraction of facial muscles. Faculty of physical therapy 19 Faculty of physical therapy 20 Faculty of physical therapy 21 Faculty of physical therapy 22 Hormonal Control of Calcium Ion Concentration Parathyroid hormone (PTH) 1, 25–dihydroxycholecalciferol (calciterol) (active vitamin D3) Calcitonin Faculty of physical therapy 23  Vitamin D3 (1, 25 (OH)2 D3) (Calcitriol) It can be obtained from diet (only few dietary sources as fat fish & egg yolk). It is formed in the skin by the action of ultraviolet light Cholecalciferol is activated in LIVER and KIDNEY Vitamin D3 increases Calcium levels in blood by acting on: Intestine, kidney, and Bone Faculty of physical therapy 24  Calcitonin (Thyrocalcitonin) - Released from Parafollicular cells of thyroid gland. - It is a polypeptide hormone (32 AA). - It lowers serum calcium and phosphate levels. - It is antagonistic to PTH as regards Ca2+ but similar to PTH as regards PO4. - Calcitonin hormone lower blood calcium level by its action on bones and kidneys. Faculty of physical therapy 25 Faculty of Physiotherapy 26 1- Parathyroid H. increase the calcium level in bones. Blood 2- Calcitonin is antagonistic to PTH as regards Ca2+ but similar to PTH as regards PO4 3- Hyperparathyroidism leads to tetany, due to increased Ca levels hypercalcemia 4- Parathyroid H. increases Ca absorption from the intestine directly By formation of vitamin D Faculty of Physiotherapy 27 Faculty of physical therapy 28