Calcium homeostasis and metabolism Flashcards
How does hypocalcaemia present?
Paraesthesia (fingers, toes, perioral) Muscle weakness Tetany/cramps Fatigue Bronchospasm Fits
Which two signs suggest hypocalaemia?
Chovsteks (facial nerve)
Trousseau (carpopedal spasm)
What is a sign of hypocalaemia on an ECG?
Prolonged QT interval
What are the causes of hypocalcaemia?
Hypoparathyroidism Vitamin D deficiency (rickets, osteomalacia) Chronic renal failure Pancreatitis Metastases Rhabdomyolysis (statins)
How is acute hypocalcaemia?
IV calcium gluconate
What are the causes of hypoparathyroidism?
DiGeorge syndrome Autoimmune Surgery/radiation Malignancy Hypomagnesaemia Idiopathic
What is the management of chronic hypocalcaemia?
Calcium supplement
Vitamin D - 1alpha calcidol (tablet) or cholecalciferol (injection)
How does hypomagnesaemia cause hypocalcaemia?
Magnesium is essential for calcium release from cells >
Intracellular calcium is high >
PTH release inhibited >
Skeletal and muscle receptors less sensitive to calcium
How is hypomagnesaemia treated?
Calcium and magnesium replacement
What are the causes of hypomagnesaemia?
Alcohol Medication (thiazides, PPI) GI illness Pancreatitis Malabsorption
What is pseudohypoparathyroidism?
Genetic dysfunction of G protein Gs alpha subunit causing PTH resistance
How does pseudohypoparathyroidism present?
Low calcium Elevated PTH Bone abnormalities/McCune Albright Obesity Subcutaneous calcification Learning disability Brachdactyly
What is pseudo-pseudohypoparathyroidism?
Pseudohypoparathyroidism but with normal calcium levels
Can you change between pseudo-pseudohypoparathyroidism to pseudohypoparathyroidism?
Yes
Where do humans get their vitamin D from?
The sun and their diet
How do the terms rickets and osteomalacia differ?
Softening of the bones
Rickets - children
Osteomalacia - adults
How does vitamin D deficiency arise?
Dietary deficiency Lack of sunlight Malabsorption Chronic renal failure Anticonvulsants
How does osteomalacia present?
Low calcium Proximal myopathy Rib deformity Limb deformity Bone tenderness Pseudo/fractures Dental defects (caries)
What x-ray feature is associated with vitamin D deficiency?
Looser zones/pseudofractures
What deficiency does chronic renal failure cause?
Vitamin D deficiency –> secondary hypoparathyroidism
What changes to vitamin D does chronic renal failure cause?
25 OH vit D may be normal or high
1,25 OH vit D will be low
How should chronic renal failure be treated in terms of vitamin D correction?
Titrate levels of vitamin D to match PTH Phosphate binders (to get rid of elevated blood phosphate)
What are the biochemical results of someone with UV related vitamin D deficiency?
Low calcium Low phosphate High alk phosphate Low vitamin D High PTH
What are the long term risks of vitamin D deficiency?
Fractures Osteomalacia/rickets Colonic cancer Diabetes Heart disease
What is the treatment for chronic vitamin D deficiency?
Vitamin D3 tablets
Calcitriol
Alfacalcidol
Adcal D3 (calcium + vit D)
What is X-linked hypophosphataemia? What other name does it go by?
Genetic mutation causing decreased phosphate reabsorption and thus rickets
Vitamin D resistant rickets
What is the biochemical profile of someone with hypophosphataemia?
High vitamin D
Low phosphate
How is X-linked hypophosphataemia managed?
Phosphate and vitamin D supplements +/- surgery to correct genu varum
