Lecture 24 Clinical Calcium Homeostasis Flashcards
Name dietary sources of calcium
- Milk, cheese and other dairy foods
- Broccoli, Cabbage and Okra
- Soya beans
- Tofu
- Nuts
- Bread and anything with fortified flour
- Fish where you eat the bones- sardines and pilchards
What are the functions of calcium
- Bone formation
- Cell division & growth
- Muscle contraction
- Neurotransmitter release
What percentage of calcium is found in the
Cells
ECF
Bone
Cells-1%
ECF- 0.1%
Bone- 98.9%
In the plasma what percentage of calcium is bound to albumin, non-ionised and ionised
- 45% bound mainly to albumin
- 10% non-ionised or complexed to citrate PO4
- 45% ionised (biologically important)
What is the normal calcium range in the plasma
2.20-2.60 mmol/l
How do you calculate free calcium
– Adjust Ca2+ by 0.1mmol/l for each 5g/l reduction in albumin from 40g/l
Ca (mmol/L) = Ca measured (mmol/L) + 0.020 (40 - albumin (g/L))].
Name sources of vitamin D
- Oily fish – such as salmon, sardines and mackerel
- Eggs
- Fortified fat spreads
- Fortified breakfast cereals
- Some powdered milks
Name groups at risk of vitamin D
- Pregnant
- Children
- Elderly
- Black
- Asian
When is PTH secreted
In réponse to low calcium from the parathyroid Gand
Explain Vitamin D metabolism
- Vit D is metabolised first to 25 hydroxyvitaimn D
- Transported to kidneys where it is converted to active form under the influence of parathyroid hormones
- Effects of this are mineralisation of bone, increased calcium and phosphate reabsorption in the kidneys and increased calcium absorption in the gut
- Excess Vit D is excreted into the bile
What are the neurological symptoms of acute hypocalcaemia
Tetany Parathesia Muscle twitching Carpopedal Spasm Trousseau's sign Chovstek's sign Seizures Laryngospasm Bronchospasm
What are the cardiac symptoms of acute hypocalcaemia
Prolonged QT interval
Hypotension
Heart failure
Arrythmia
What causes low PTH
Direct damage to Parathyroid gland Post surgical Autoimmune Infiltration Radiation induced HIV infection
What causes high PTH
In response to hypocalcaemia caused by Renal disease Vitamin D deficiency Hypomagnesium Acute respiratory alkalosis cute pancreatitis
What drugs can cause hypocalcaemia
Bisphophates Calcitonin Cinacalet Calcium chelators Foscarnet Ohenytoin Fluoride poisoning
What investigations can be done if hypocalcaemia is detected
- Ca & Vit D intake
- Neck surgery
- Autoimmune disorders
- Medications
- Family history
- Neck scars
- ECG- Calcium plays a key role in cardiac muscle contraction and metabolism, abnormal heart rate, slow it down
- Serum calcium
- Albumin
- Phosphate
- PTH
- U&Es
- Vitamin D
- Magnesium
What is Pseudohypoparathyroidism
Presents at childhood
Target organ (kidney and bone) unresponsiveness to PTH
hypocalcemia, hyperphosphatemia
Elevated PTH
How is mild hypocalcaemia treated
oral calcium
If vitamin D deficient treat with supplement
If low magnesium- replace magnesium
How is severe hypocalcaemia treated
IV calcium gluconate
ECG monitoring
Who should be taking Vitamin D supplements and how mcuh
• Everyone age 5 years and above should consider taking a daily supplement of 10 micrograms vitamin D, particularly during the winter months (October – March).
What are the causes of hypercalcaemia
Sporadic malignancy Vitamin D intoxication Chronic granulomatous disorders (TB, sarcoidosis, Wegner's) Hyperthyroidism Acromegaly
Clinical features of hypercalcaemia
Polyuria Polydipsia Anorexia Nausea and vomiting Muscle weakness Decreased concentration Shortening of the QT interval
What is the management of multiple endocrine neoplasia
- 0.9% Saline 4-6 litres over 24 hours
- Monitor for fluid overload
- Consider dialysis if severe renal failure
- After rehydration, intravenous bisphosphonates
- Zolendronic acid 4mg over 15 mins
- Give more slowly and consider dose reduction if renal impairment
- Calcium will reach nadir at 2-4 days
Whats the 2nd line management for MEN
Glucocorticoids- lymphoma, granulomatous disease, Vit D poisoning
Calcitonin- if there’s poor response to bisphosphates
Calcimimetics- hypercalcaemia
Parathyroidectomy- acute presentation of primary hyperparathyroid
