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2ND YEAR SYSTEMS: Diabetes and Endocrinology > Clinical calcium homeostasis > Flashcards

Clinical calcium homeostasis Flashcards

1
Q

Dietary sources of calcium

A

milk, cheese and other dairy foods

green leafy vegetables– such as broccoli, cabbage and okra, but not spinach

soya beans

Tofu

nuts

bread and anything made with fortified flour

fish where you eat the bones– such as sardines and pilchards

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2
Q

Functions of calcium (4)

A

Bone formation

Cell division and growth

Muscle contraction

Neurotransmitter release

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3
Q

Normal range of Calcium in the blood in clinical practice

A

2.20 - 2.60 mmol/l

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4
Q

What effect does increased albumin have on free calcium

A

free calcium decreases

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5
Q

How does acidosis lead to hypercalcaemia

A

acidosis increases ionised (free) calcium

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6
Q

Groups at risk of vitamin D deficiency

A

infants and children

pregnant and breastfeeding women, particularly teenagers and young women

Elderly

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7
Q

What types of cells respond directly to changes in calcium concentrations

A

Parathyroid Chief cells

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8
Q

Alterations in ECF Ca2+ levels are transmitted into the parathyroid cells via which receptor

A

Calcium-sensing receptor

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9
Q

Which hormone is secreted in response to a fall in calcium? what is it’s direct effect

A

Parathyroid hormone

promotes reabsorbtion of calcium from renal tubules & bone into the blood

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10
Q

What bone problems can persistent high PTH level lead to

A

Osteopenia

Osteoporosis

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11
Q

How does PTH affect vitamin D

A

It mediates the conversion of vit D from its inactive to active form

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12
Q

Where does vitamin D activation occur?

A

In the kidney

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13
Q

Pathway of vitamin D

A

Sunlight/diet

converted first into vit d 25-hydroxylase in the liver (inactive form)

Moves to kidney - here it becomes activated. It then moves to the gut

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14
Q

Hypocalcaemia clinical range

A

Serum calcium <2.20

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15
Q

Clinical features of hypocalcaemia

A

Neuromuscular irritability (tetany)

Spasms - carpopedal spasm

Anxious/irritable

cardiac problems (arrhythmias, HF, hypotension), papilloedema

Symptoms typically develop when serum calcium <1.9mmol/L

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16
Q

Clinical signs of hypocalcaemia

A

Chovstek’s sign

Trosseau’s sign

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17
Q

What is Trosseau’s sign/how do you test it?

A

carpopedal spasm caused by inflating the blood-pressure cuff to a level above systolic pressure for 3 minutes

Hand curls inwards at wrist

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18
Q

What is Chovstek’s sign/how do you test it?

A

Ask patient to relax facial nerves. Tap the facial nerve just anterior to earlobe or below the zygomatic arch + corner of mouth

+ response = twitching of the lip at the corner of the mouth to spasm of all facial muscles, depending on severity of hypocalcaemia

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19
Q

What surgery can cause damage to the parathyroid gland?

A

total thyroidectomy

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20
Q

Causes of hypocalcaemia (6)

A

Disruption of parathyroid gland due to total thyroidectomy. May be temporary or permanent

Following selective parathyroidectomy (usually transient & mild)

Severe vitamin D deficiency

Mg2+ deficiency

Cytotoxic drug-induced hypocalcaemia

Pancreatitis, rhabdomyolysis and large volume blood tranfusions

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21
Q

Most common causes of low PTH

A

Gentic disorders

Autoimmune

HIV infection

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22
Q

Most common causes of high PTH - secondary hyperparathyroidism in response to hypocalcaemia

A

Vit D deficiency

Pseudohypoparathyroidism

Hypomagnesemia

Renal disease

Acute pancreatitis

Acute respiratory alkalosis

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23
Q

Most common drugs causing hypocalcaemia

A

Inhibitors of bone resorption - bisphosphonates

24
Q

Investigations done to diagnose hypocalcaemia (8)

A 
ECG
Serum calcium
Albumin
Phosphate
PTH
U&amp;Es - check if PTH is high
Vitamin D
Magnesium - check if PTH is low or normal
25
What is the link between serum albumin and calcium?
If serum albumin levels fall so do the calcium levels
26
If magnesium levels are normal but you have low/normal PTH then what are the probable diagnoses
hypoparathyroidism or calcium sensing receptor defect
27
If you have high PTH and high levels of creatinine what is the probable diagnosis
Renal failure
28
Vitamin D deficiency: | what results would you expect for total calcium, ionised calcium, phosphate and PTH
Total calcium = low Ionised calcium = low Phosphate = low PTH = high (due to low Ca2+)
29
Link between PTH and calcium
Parathyroid hormone is secreted by the parathyroid glands and is the most important regulator of blood calcium levels Low calcium levels stimulate PTH secretion, whereas high calcium levels prevent the release of PTH
30
Function of vitamin D
Vitamin D promotes calcium absorption in the gut and maintains blood calcium levels to enable normal mineralization of bone and prevent abnormally low blood calcium levels that can then lead to tetany So increase in vit d => increase in Ca2+ less vit D = less Ca2+ being absorbed
31
Hypoparathyroidism: What results would you expect for total calcium, ionised calcium, phosphate and PTH?
Total calcium = low Ionised calcium = low Phosphate = High (low PTH means low calcium levels so serum phosphorus increases as its function is to help the body absorb and utilise calcium PTH = low
32
How might hypoparathyroidism result (5)
Agenesis (DiGeorge syndrome - underdeveloped parathyroid glands) Destruction (neck surgery, autoimmnue disease) Infiltration (haemochromatosis or Wilson's disease) Reduced secretion of PTH Resistance to PTH
33
What is pseudohypoparathyroidism?
Group of diseases defined by target organ unresponsiveness to PTH Presents in childhood
34
What is pseudohypoparathyroidism characterised by?
Hypocalcaemia Hyperphophataemia Elevated PTH (not binding to target organs so staying in blood)
35
What are symptoms of Albright’s heriditary Osteodystrophy
Obesity, short stature, shortening of the metacarpal bones
36
What is it called if you have AHO alone without abnormalities of calcium or parathyroid hormone
pseudo-pseudohypoparathyroidism
37
Treatment of mild hypocalcaemia (asymptomatic >1.9 mmol/L)
Commence oral calcium tablets If post thyroidectomy repeat calcium 24 hours later If vit D deficient, start vitamin D If low Mg2+, stop any precipitating drug and replace Mg2+
38
What types of drugs can cause hypomagnesemia
antibiotics chemotherapeutic agents diuretics proton-pump inhibitors
39
Treatment of severe hypocalcaemia emergency
Administer IV calcium gluconate - repeat if needed ECG monitoring Treat underlying cause like respiratory alkalosis
40
In patients with severe renal impairment require vitamin D therapy what should you give them and why?
Alfacalcidol or calcitriol These are already in active form In renal disease kidney isn't functioning properly so can't hydroxylate vitamin D into active form
41
A calcium level of >3.5 mmol/L requires what?
Urgent correction due to risk of dysrhthmia and coma
42
Main causes of hypercalcaemia (2)
Primary hyperparathyroidism Malignancy
43
Clinical features of hypercalcaemia (6)
``` Polyuria Thirst Anorexia Nausea + vomiting Muscle weakness Constipation ```
44
Phrase that helps you remember hypercalcaemia symptoms
Bones, stones, groans + psychic mones Renal stones Muscle weakness Confusion/decreased concentration Depression
45
Example patient presenting with hypercalcaemia of malignancy
``` Weight loss Changed bowel habit Low PTH High Calcium Heavy smoker + chronic cough ```
46
Investigations for Hypercalcaemia (8)
U&Es Ca2+ PO4 - increased points to cancer diagnosis Alk phos Myeloma screen Serum ACE PTH - if high then points to hyperparathyroidism, if low => cancer consider ECG
47
Most common causes of Primary hyperparathyroidism
Adenoma | Hyperplasia of all glands
48
Investigations for primary hyperparathyroidism (6)
Ca2+ and PTH U+E Abdominal imaging DEXA for osteoporosis 24hr urine collection for Ca2+ Vit D Parathyroid USS, CT, PET
49
When would a patient be indicative for parathyroid surgery?
If patient is <50, has osteoporosis on DEXA, normal serum calcium, kidney stones, has symptoms of hypercalcaemia
50
Treatment of primary hyperparathyroidism
Parathyroid surgery Medical management - generous fluid intake, Cinacalcet - mimics effect of Ca2+ on calcium sensing receptor on Parathyroid chief cells causing fall in PTH and subsequently low Ca2+ levels)
51
What is Familial Hypocalciuric | Hypercalcaemia
Autosomal dominant inherited disorder that causes hypercalcemia and hypocalciuric (low levels of urinary Ca2+) Affects the calcium sensing receptor Positive family history, screen young family members for diagnosis. No evidence of abnormal parathyroid tissue on ultrasound or isotope scan
52
Multiple Endocrine | Neoplasia type 1 (MEN-1)
Main causes: Primary hyperparathyroidism (>95%) Pancreatic or Pituitary MENIN mutation on chromosome 11
53
Multiple Endocrine | Neoplasia type 2 (MEN-2)
Associated with: Medullary thyroid cancer Phaeochromocytoma Primary hyperparathyroidism RET mutation
54
What are Multiple Endocrine | Neoplasias
Syndromes where there are functioning hormone-producing tumours in multiple organs, these are: MEN-1 MEN-2
55
Management of hypercalcaemia
Rehydration - monitor for fluid overload, consider dialysis if severe renal failure after rehydration - IV bisphophonates
56
2nd line management of hypercalcaemia
Glucocorticoids Calcitonin Calcimimetics Parathyroidectomy

2ND YEAR SYSTEMS: Diabetes and Endocrinology (21 decks)

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