Calcitonin, parathyroid hormone and calcium balance

Question 1

sites of calcium storage are called?

Answer 1

calcium pools

Question 2

True/False: Childrens net increase in Calcium is 0?

Answer 2

False: the adult net increase in calcium is 0, calcium is essential for growth.

Question 3

Calcium pools in the body is what?

Answer 3

1kg

Question 4

What can small decreases in serum calcium levels result in?

Answer 4

Clinical symptoms e.g. tetary and seizures

Question 5

about how much of the calcium ingested is absorbed?

Answer 5

half

Question 6

What are the hormones responsible for calcium homeostasis?

Answer 6

Parathyroid hormone
Calcitonin
Vitamin D

Question 7

Where is PTH produced?

Answer 7

parathyroid gland

Question 8

Describe the parathyroid gland

Answer 8

located around edges of thyroid
usually have 4 
rich blood supply
chief cells secrete PTH
PTH is a peptide hormone - 84 aa

Question 9

\what is the precursor of PTH?

Answer 9

Pre-Pro-PTH

Question 10

What does the pre sequence of PTH do?

Answer 10

directs it into the secretory pathway of the cells

Question 11

Describe the pathway taken of PTH

Answer 11

comes of ribosome into ER, as it enters PRE is cleaved off, as it travels to golgi pro is cleaved off

Question 12

Describe the secretions of PTH

Answer 12

occurs continuously
cleared from circulation rapidly
cleared by the kidney
principle regulator of secretion
calcium levels are detected by chief cells

Question 13

what is Hypercalcaemia?

Answer 13

High calcium levels = PTH secretion surpessed

Question 14

What is Hypocalcaemia?

Answer 14

Low calcium levels =PTH secretion stimualted

Question 15

What kind of feedback to the parathyroid gland reduces PTH secretion?

Answer 15

Negative feedback

Question 16

Where is Calcitonin produced?

Answer 16

Parafollicular cells (C-cells) of the thyroid gland.

Question 17

What is calcitonin?

Answer 17

peptide hormone 32 aa

produced fro large peptide precursor

Question 18

What stimulates calcitonin secretion?

Answer 18

Hypercalcaemia - high blood calcium

Question 19

What are the sources of vitamin D?

Answer 19

Diet - fish and eggs

Formation in skin - UV light

Question 20

what is the major form of Vitamin D in circulation?

Answer 20

25-hydrocycholecalciferol

Question 21

what happens to 25-hydrocycholecalciferol in the kidney?

Answer 21

A hydroxyl group is added at position 1 to give 1,25-dihydroxycholecalciferol (CALCITROL) = most biologically active

Question 22

What is the activity of calcium regulation by the kidney regulated by?

Answer 22

1-alpha-hydroxylase - dependant on the serum calcium and phosphate levels

Question 23

What renders 1-alpha-hydroxylase inactive?

Answer 23

removal of hydroxyl group

Question 24

what activates 1-alpha-hydroxylase?

Answer 24

low calcium, thus PTH stimulates it and calcitonin surpasses it

Question 25

what is the condition Hypercalcaemia?

Answer 25

PTH over secretion | due to benign tumour of one of 4 parathyroid glands

Question 26

What are the symptoms of hypercalcaemia?

Answer 26

``` 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 ```

Question 27

What is the treatment of hypercalcaemia?

Answer 27

surgical removal of overactive parathyroid

Question 28

What is HYPOCALCAEMIA?

Answer 28

under secretion of PTH increased excitability of nervous tissue causing paraesthesia (tingling) attacks of tetany and seizures no known cause

Question 29

Resistance to PTH in hypocalcaemia and symptoms

Answer 29

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

Question 30

Treatment of hypocalcaemia

Answer 30

oral calcium and calcitrol

Question 31

What does Vitamin D deficiency cause?

Answer 31

decreased Ca uptake from gut causes rickets in children osteomalacia in adults it is a result of failure on the calcification of bone

Question 32

what are the effects of vitamin D deficiency in children?

Answer 32

failure of bone remodelling so that ends of bones are swollen, bow legs/knock knees

Question 33

What are the effects of Vitamin D deficiency in adults?

Answer 33

``` Bone pain decreased bone density fractures muscle weakness serum calcium low = tetany ```

Question 34

Treatment of Vitamin D deficiency?

Answer 34

Vitamin D supplements