Calcitonin, parathyroid hormone and calcium balance Flashcards
sites of calcium storage are called?
calcium pools
True/False: Childrens net increase in Calcium is 0?
False: the adult net increase in calcium is 0, calcium is essential for growth.
Calcium pools in the body is what?
1kg
What can small decreases in serum calcium levels result in?
Clinical symptoms e.g. tetary and seizures
about how much of the calcium ingested is absorbed?
half
What are the hormones responsible for calcium homeostasis?
Parathyroid hormone
Calcitonin
Vitamin D
Where is PTH produced?
parathyroid gland
Describe the parathyroid gland
located around edges of thyroid usually have 4 rich blood supply chief cells secrete PTH PTH is a peptide hormone - 84 aa
\what is the precursor of PTH?
Pre-Pro-PTH
What does the pre sequence of PTH do?
directs it into the secretory pathway of the cells
Describe the pathway taken of PTH
comes of ribosome into ER, as it enters PRE is cleaved off, as it travels to golgi pro is cleaved off
Describe the secretions of PTH
occurs continuously cleared from circulation rapidly cleared by the kidney principle regulator of secretion calcium levels are detected by chief cells
what is Hypercalcaemia?
High calcium levels = PTH secretion surpessed
What is Hypocalcaemia?
Low calcium levels =PTH secretion stimualted
What kind of feedback to the parathyroid gland reduces PTH secretion?
Negative feedback
Where is Calcitonin produced?
Parafollicular cells (C-cells) of the thyroid gland.
What is calcitonin?
peptide hormone 32 aa
produced fro large peptide precursor
What stimulates calcitonin secretion?
Hypercalcaemia - high blood calcium
What are the sources of vitamin D?
Diet - fish and eggs
Formation in skin - UV light
what is the major form of Vitamin D in circulation?
25-hydrocycholecalciferol
what happens to 25-hydrocycholecalciferol in the kidney?
A hydroxyl group is added at position 1 to give 1,25-dihydroxycholecalciferol (CALCITROL) = most biologically active
What is the activity of calcium regulation by the kidney regulated by?
1-alpha-hydroxylase - dependant on the serum calcium and phosphate levels
What renders 1-alpha-hydroxylase inactive?
removal of hydroxyl group
what activates 1-alpha-hydroxylase?
low calcium, thus PTH stimulates it and calcitonin surpasses it
what is the condition Hypercalcaemia?
PTH over secretion
due to benign tumour of one of 4 parathyroid glands
What are the symptoms of hypercalcaemia?
SUBPERIOSTEAL RESORPTION OF BONE - sometimes extensive enough to cause cyst formation - pain and difficulty walking Renal calculi (kindey stones) causes renal colic and renal tract infections
What is the treatment of hypercalcaemia?
surgical removal of overactive parathyroid
What is HYPOCALCAEMIA?
under secretion of PTH
increased excitability of nervous tissue causing paraesthesia (tingling) attacks of tetany and seizures
no known cause
Resistance to PTH in hypocalcaemia and symptoms
decrease of relevant G proteins in bone and kidney. PTH receptor ineffective
mental deficiency, shortening of metacarpals and rounds of face.
Calcification in muscle and brain
Treatment of hypocalcaemia
oral calcium and calcitrol
What does Vitamin D deficiency cause?
decreased Ca uptake from gut
causes rickets in children
osteomalacia in adults
it is a result of failure on the calcification of bone
what are the effects of vitamin D deficiency in children?
failure of bone remodelling so that ends of bones are swollen, bow legs/knock knees
What are the effects of Vitamin D deficiency in adults?
Bone pain decreased bone density fractures muscle weakness serum calcium low = tetany
Treatment of Vitamin D deficiency?
Vitamin D supplements
