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Endocrinology > Calcitonin, parathyroid hormone and calcium balance > Flashcards

Calcitonin, parathyroid hormone and calcium balance Flashcards

1
Q

sites of calcium storage are called?

A

calcium pools

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2
Q

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

A

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

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3
Q

Calcium pools in the body is what?

A

1kg

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4
Q

What can small decreases in serum calcium levels result in?

A

Clinical symptoms e.g. tetary and seizures

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5
Q

about how much of the calcium ingested is absorbed?

A

half

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6
Q

What are the hormones responsible for calcium homeostasis?

A

Parathyroid hormone
Calcitonin
Vitamin D

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7
Q

Where is PTH produced?

A

parathyroid gland

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8
Q

Describe the parathyroid gland

A 
located around edges of thyroid
usually have 4 
rich blood supply
chief cells secrete PTH
PTH is a peptide hormone - 84 aa
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9
Q

\what is the precursor of PTH?

A

Pre-Pro-PTH

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10
Q

What does the pre sequence of PTH do?

A

directs it into the secretory pathway of the cells

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11
Q

Describe the pathway taken of PTH

A

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

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12
Q

Describe the secretions of PTH

A 
occurs continuously
cleared from circulation rapidly
cleared by the kidney
principle regulator of secretion
calcium levels are detected by chief cells
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13
Q

what is Hypercalcaemia?

A

High calcium levels = PTH secretion surpessed

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14
Q

What is Hypocalcaemia?

A

Low calcium levels =PTH secretion stimualted

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15
Q

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

A

Negative feedback

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16
Q

Where is Calcitonin produced?

A

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

17
Q

What is calcitonin?

A

peptide hormone 32 aa

produced fro large peptide precursor

18
Q

What stimulates calcitonin secretion?

A

Hypercalcaemia - high blood calcium

19
Q

What are the sources of vitamin D?

A

Diet - fish and eggs

Formation in skin - UV light

20
Q

what is the major form of Vitamin D in circulation?

A

25-hydrocycholecalciferol

21
Q

what happens to 25-hydrocycholecalciferol in the kidney?

A

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

22
Q

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

A

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

23
Q

What renders 1-alpha-hydroxylase inactive?

A

removal of hydroxyl group

24
Q

what activates 1-alpha-hydroxylase?

A

low calcium, thus PTH stimulates it and calcitonin surpasses it

25
Q

what is the condition Hypercalcaemia?

A

PTH over secretion

due to benign tumour of one of 4 parathyroid glands

26
Q

What are the symptoms of hypercalcaemia?

A 
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
27
Q

What is the treatment of hypercalcaemia?

A

surgical removal of overactive parathyroid

28
Q

What is HYPOCALCAEMIA?

A

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

29
Q

Resistance to PTH in hypocalcaemia and symptoms

A

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

30
Q

Treatment of hypocalcaemia

A

oral calcium and calcitrol

31
Q

What does Vitamin D deficiency cause?

A

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

32
Q

what are the effects of vitamin D deficiency in children?

A

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

33
Q

What are the effects of Vitamin D deficiency in adults?

A 
Bone pain
decreased bone density
fractures
muscle weakness
serum calcium low = tetany
34
Q

Treatment of Vitamin D deficiency?

A

Vitamin D supplements

Endocrinology (12 decks)

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