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Endocrinology > Calcium Metabolism and Disorders > Flashcards

Calcium Metabolism and Disorders Flashcards

1
Q

Describe vitamin D metabolism

A

Taken in via skin and diet
25 hydroxylated in the liver
Activated in the kidney by PTH as it stimulates further hydroxylation

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2
Q

Which element is needed for PTH production

A

Magnesium

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3
Q

How does PTH impact osteoblast activity

A

It inhibits sclerostin which is an inhibitor of osteoblasts

Overall it allows an increase in osteoblast activity

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4
Q

Describe bone metabolism

A

Inorganic pyrophosphate – under stimulation of TNAP it is converted to inorganic phosphate
The inorganic phosphate joins with calcium to form hydroxyapatite – mineralisation building block of bone

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5
Q

List the acute symptoms hypercalcaemia

A

Thirst and dehydration
Confusion
Polyuria

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6
Q

List the chronic symptoms of hypercalcaemia

A 
Myopathy
Fractures
Osteopenia
Depression
Hypertension
Pancreatitis
Duodenal ulcers 
Renal calculi
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7
Q

Which tests do you do to diagnose hypercalcaemia

A

PTH levels - may be raised if primary hyperparathyroidism
Serum calcium - will be raised
Urine calcium excretion- will be increased

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8
Q

If PTH levels are high and urinary calcium excretion is raised what is the pathology

A

Parathyroid issue

Primary or tertiary hyperparathyroidism

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9
Q

If PTH levels are high and urinary calcium excretion is low what is the pathology

A

Parathyroid issue

Familial hypocalciuric hypercalcemia

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10
Q

If PTH levels are low and ALP is low what is the pathology

A

Bone pathology
Myeloma
Vit D Toxicity
Milk-Alkali

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11
Q

If PTH levels are low and ALP is high what is the pathology

A

Bone pathology
Metastases
Sarcoidosis
Thyrotoxicosis

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12
Q

List the causes of hypercalcaemia

A

Primary hyperparathyroidism
Malignancy

Drugs: vit D and thiazides
Granulomatous disease
Familial Hypocalciuric Hypercalcaemia
High bone turnover - bedridden, thyrotoxic, Paget’s

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13
Q

how can malignancy lead to hypercalcaemia

A

Metastatic Bone destruction - calcium released from bone

PTHrp from solid tumours - peptide that mimics effect of PTH
Osteoclast activating factors

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14
Q

Describe the acute treatment for hypercalcaemia

A

Fluids - rehydrate with 0.9% saline, 4-6L in 24 hours
Once rehydrated you can give loop diuretics to increase Ca excretion
Bisphosphonates- single dose will lower Ca over 2-3d
High dose steroids for sarcoid patients for at least a year

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15
Q

What is a sestamibi scan

A

Use scan taken up only by thyroid and another taken up by both thyroid and para – subtract one from the other to look at parathyroid only

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16
Q

How do you manage primary hyperparathyroidism

A

Surgery - definitive treatment
Diet and drugs - less effective
Cinacalcet - mimics calcium effect on PTH receptor to decrease PTH and overall calcium

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17
Q

List the indications for a parathyroidectomy

A

End organ damage - bone disease, gastric ulcers, renal stones and osteoporosis
Under 50 y/o
very high calcium

18
Q

What is primary hyperparathyroidism

A

Primary overactivity of Parathyroid gland i.e. adenoma

Will have high calcium and PTH

19
Q

What is secondary hyperparathyroidism

A

Physiological response to low calcium or Vit D

Will have low calcium but high PTH

20
Q

What is tertiary hyperparathyroidism

A

Parathyroid becomes autonomous after many years of overactivity e.g. renal failure
High calcium and PTH

21
Q

Which genetic conditions can lead to hyperparathyroidism

A

MEN 1/2 - almost always develop a parathyroid adenoma with hypercalcaemia at a young age
Familial isolated hyperparathyroidism - adenoma

22
Q

Describe familial hypocalciuric hypercalcaemia

A

Inherited condition - autosomal dominant
Often asymptomatic as only gives mild hypercalcaemia
Low calcium excretion from urine leading to high serum calcium

23
Q

What are the symptoms of hypocalcaemia

A 
Paranesthesia - fingers, toes and perioral 
Muscle cramps and tetany 
Muscle weakness 
Fatigue 
Bronchospasm or laryngospasm
Fits
24
Q

What are the signs of hypocalcaemia

A

Chvostek’s sign - tapping over facial nerve
Trosseau’s sign - spasm in wrist when blood pressure cuff put on
QT prolongation

25
Q

How do you treat acute hypocalcaemia

A

IV calcium gluconate - 10ml 10% over 10 mins

Given in 50ml saline or dextrose

26
Q

What can cause hypoparathyroidism

A 
Congenital absence (Di George syndrome)
Destruction (surgery, radiotherapy, malign)
Autoimmune
Hypomagnesaemia
Idiopathic
27
Q

Describe the long term management of hypocalcaemia

A

Calcium supplement - 1-2g per day

Vitamin D supplement

28
Q

Describe hypomagnesaemia

A

Calcium release is dependent on Mg
If Mg low then intracellular Ca becomes high and PTH release is inhibited
Skeletal and muscle receptors less sensitive to PTH

29
Q

How do you treat hypomagnesaemia

A

Replace with calcium and magnesium

30
Q

List causes of hypomagnesaemia

A 
Alcohol 
Drugs: thiazide and PPI 
GI illness 
Pancreatitis 
Malabsorption
31
Q

What is pseudohypoparathyroidism

A

genetic defect - dysfunction of G protein (Gs alpha subunit)
Gene = GNAS 1
Low calcium but high PTH due to PTH resistance

32
Q

What are the symptoms of pseudohypoparathyroidism

A 
Bone abnormalities 
Obesity 
Subcutaneous calcification 
Learning disability 
Brachydactyly - shortened 4th metacarpal
33
Q

What is pseudo-pseudohypoparathyroidism

A

Albright’s Herditary Osteodystrophy

However no altered PTH level so normal calcium

34
Q

What causes Rickets and Osteomalacia

A

Vitamin D deficiency

Can be caused by dietary deficiency, malabsorption, renal failure or lack of sunlight

35
Q

What are the long term consequences of vitamin D deficiency

A

Bone Disease:
Demineralisation/ Fractures
Osteomalacia/ Rickets

Malignancy - colon
Heart disease

36
Q

How do you treat vitamin D deficiency

A

Vitamin D supplements - tablets

Combined calcium and vitamin D supplement

37
Q

Which cancers are associated with hypercalcaemia

A 
Those with bony mets 
Breast
Lung
Bone
Multiple myeloma
38
Q

If PTH is low but calcium is high what does this suggest

A

That the excess calcium is coming from somewhere else and is not due to excess PTH (hyperparathyroidism)

39
Q

How do granulomatous diseases cause hypercalcaemima

A

Granulomas can hydroxylate vit D increasing the levels of its active form
Examples: sarcoidosis and TB

40
Q

What is the most common cause of hypercalcaemia in the general population

A

Parathyroid adenoma

Endocrinology (13 decks)

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