Endocrine Physiology PDF - Parathyroid and Calcium Regulation

Endocrine Physiology parathyroid and calcium regulation BY Dr. Esraa Ahmed Physiology Department Faculty Of Medicine Badr University in Cairo Dr. Esraa Ahmed  Learning Objec...

Endocrine Physiology parathyroid and calcium regulation BY Dr. Esraa Ahmed Physiology Department Faculty Of Medicine Badr University in Cairo Dr. Esraa Ahmed  Learning Objectives By the end of this course the student will be able to:  Describe the functions of parathyroid hormone.  Discuss the effect of parathyroid hormone on  kidney ,bone and intestine.  Mention the factors stimulate the release of  parathyroid hormone  Mention the manifestation of  hyperparathyroidism and hypo-parathyroidism.  List the types of Tetany related to calcium level.  Recognize physiological importance of calcium.  Discuss calcium homeostasis. Dr. Esraa Ahmed  Parathyroid Glands  Four bean-shaped parathyroid glands.  Found in pairs on the posterior surface of the 2 lobes of the thyroid gland. Dr. Esraa Ahmed  Parathyroid hormone  Site of release: chief cells of the parathyroid gland.  Physiological actions: regulation of the Ca+2 level in the blood. SO, it is essential for life its main function is to ↑ plasma Ca+2 level. ↓ plasma Po+4 level. Through acting on 3 target organs: Dr. Esraa Ahmed Dr. Esraa Ahmed  Action of Parathyroid hormone 1- On Bone ++ osteoclasts   breadown of bone matrix  mobilization of Ca++ from bone to plasma (bone resorption).  N.B normal level of parathyroid hormone ++ both osteoblast and osteoclast. But very high level ++ osteoclast only ) Dr. Esraa Ahmed  Action of Parathyroid hormone 2- On Kidney: Ca+2 reabsorption.  Ca+2 level Po4 excretion.  ↓ Po4 level 3- On intestine: PTH (+) vitamin D3 ↑ ca++ absorption from small intestine. So, this action of PTH is indirect through (+) of vitamin D3. Dr. Esraa Ahmed  Regulation of Parathyroid Glands Regulation of PTH production and release is dependent on serum calcium levels. Remember: there is no higher control on parathyroid gland from hypothalamus and pituitary Dr. Esraa Ahmed HYPERPARATHYROIDISM Dr. Esraa Ahmed  Causes of hyperparathyroidism Primary hyperparathyroidism, An abnormality of the parathyroid glands causes inappropriate, excess PTH secretion (e.g. parathyroid adenomas) PTH are elevated and blood levels of Ca2+ is high. Secondary hyperparathyroidism, High levels of PTH occur as a compensation for hypocalcemia (e.g. vitamin D3 deficiency or chronic renal failure). PTH is elevated and blood levels of Ca2+ are low or normal but never high. Dr. Esraa Ahmed Dr. Esraa Ahmed  Manifestations (hypercalcemia) (Lethal 17mg %) Stones Abdominal Bones groans??? Dr. Esraa Ahmed  Clinical picture of hyperparathyroidism It is a disease of bones, stones and abdominal groans. 1- Bones: Increased bone resorption  bone minerals are replaced by fibrous tissue with formation of bone cysts (Osteitis fibrosa cystica)  bone pains, fractures, deformities. Dr. Esraa Ahmed  Clinical picture of hyperparathyroidism 2- kidneys: Excess Ca +2 salts are excreted in urine lead to  Renal stones  Renal colics. Dr. Esraa Ahmed  Clinical picture of hyperparathyroidism 3- GIT: (abdominal groans) peptic ulcer, nausea, Constipation. Dr. Esraa Ahmed  Cause of Hypoparathyroidism  Congenital hypoparathyroidism.  Accidental removal or injury after thyroid surgery (thyroidectomy) Characterized by hypocalcemia & hyperphosphatemia. Complete absence of PTH  death. Relative deficiency  tetany. Dr. Esraa Ahmed  Tetany A state of spastic contraction of the skeletal muscle caused by increase neuromuscular excitability as a result of decreased ionized plasma calcium level Normal blood Calcium (Ca) level is 9-11 mg/dl Dr. Esraa Ahmed  Clinical picture of tetany 1- Manifest tetany: (appear during rest) when plasma Ca++ level < 7 mg%. Manifest tetany could be manifested by  Carpopedal spasm.  Generalized convulsions.  Laryngeal & respiratory spasm  suffocation. Carpopedal spasm Dr. Esraa Ahmed  Clinical picture of tetany II- Latent tetany: (appear in stress, absent at rest) When the blood Ca++ level is between 7- 9 mg%. Latent tetany could be manifested by Trousseau’s sign Provocative tests. 1- Trousseau’s sign: 2- Chvosteck’s test: Chvosteck’s test Dr. Esraa Ahmed  Causes of tetany 1-Decreased blood ionized calcium (.i.e. hypocalcemia)  Decreased calcium intake  Hypo-parathyroidism  Vitamin D3 deficiency  Renal failure Dr. Esraa Ahmed  CALCIUM HOMEOSTASIS Dr. Esraa Ahmed  Calcium metabolism Calcium in the body:  1.5% of total body weight (1000 gm) 99% in bones (Ca++ bank) 1% in soft tissues & plasma. -Plasma level = 9 -11mg/dl (average 10 mg/dL) -it is in 2 forms: Free Bound 45% 55% - To albumin, HCO3-, HPO4 - Ionized or free Ca2+ & citrate. - Active form. - Inactive form. Dr. Esraa Ahmed Calcium metabolism Dr. Esraa Ahmed  Functions of calcium 1. Bone and teeth mineralization. 2.Blood coagulation. 3. For neuromuscular system: normal excitability of nerve and excitation contraction coupling. 4.For endocrine system: release of hormone and hormone action. Dr. Esraa Ahmed  Hormones concerned with Ca++ homeostasis 1) PTH:  hypercalcemic hormone. 2) 1, 25,di(OH) cholecalciferol (vit. D3):  hypercalcemic hormone. 3) Calcitonin:  hypocalcemic hormone. Dr. Esraa Ahmed  Vitamin D3 (1,25 (OH)2 D3): 1- On the intestine: (main) ↑ calcium absorption from intestine. 2- On the Kidney: ↑ Ca++ reabsorption. 3- On bones: + osteoblast activity and calcification of bone matrix. Dr. Esraa Ahmed Dr. Esraa Ahmed  Calcitonin (Thyrocalcitonin) : Site of release: parafollicular cells of thyroid gland. Actions: ↓ calcium level. 1- On bone: (-) osteoclasts  ↓ bone resorption. (+) osteoblasts. 2- On kidneys: (+) excretion of Ca2. 3- On intestine: (-) intestinal ca++ absorption. Dr. Esraa Ahmed Calcium homeostasis Dr. Esraa Ahmed  Quiz Parathyroid hormone exerts all the following EXCEPT: A. Increase blood phosphate. B. Activates Vit. D3. C. Increase bone resorption. D. Increase calcium reabsorption from renal tubules Dr. Esraa Ahmed  Quiz Abnormal increase in parathyroid hormone secretion may result in : A. bone deminerlaization. B. hypercalcemia. C. hypercalcuria. D. All of the above. Dr. Esraa Ahmed  References 1. Pispati H. 2013. Concise textbook of physiology for dental students. Oxford. New York.p 208- 212. Dr. Esraa Ahmed  Assignment  Compare between effect of. o Parathyroid Hormone. o calcitonin Hormone. o Vit D3. On calcium homeostasis Dr. Esraa Ahmed Dr. Esraa Ahmed