Calcium Flashcards
What is the key feature of osteoporosis?
Reduced bone mineral density – the bone structure is normal.
What are the common presentations of fractures in osteoporosis?
Smith’s fracture (radius fractures forwards, falling onto a flexed wrist)
and Colle’s fracture (radius fractures backward, falling onto an outstretched hand).
What are the risk factors for osteoporosis? (8)
Cushing’s
steroids
hyperthyroidism
age
immobility
early menopause
alcohol
low BMI.
What are the blood test findings in osteoporosis patients? (2)
Everything is normal
Decreased bone mineralisation (ALP may be raised if a recent fracture occurred)
How is osteoporosis managed? (5)
Weight-bearing exercise
Vitamin D
Alendronate (bisphosphonates)
Teriparatide (artificial PTH derivative)
HRT or SERMs (e.g., raloxifene)
What are the blood test findings in osteomalacia/rickets? (3)
Low calcium and phosphate
High ALP
High PTH
What are the causes of osteomalacia/rickets? (4)
Poor diet
Malabsorption
Renal failure
Lack of sun exposure
How does osteomalacia present clinically? (3)
Bone pain
Muscle pain
Increased fracture risk (key feature: pseudofractures, e.g., Looser’s zones)
What causes primary hyperparathyroidism? (3)
Parathyroid adenoma (most common)
Parathyroid hyperplasia
Parathyroid carcinoma
What is osteomalacia?
Vitamin D deficiency, impaired bone mineralisation and bone structure is ABnormal
What are the bone features in primary hyperparathyroidism? (2)
Tends to affect the radius especially
Untreated cases lead to osteitis fibrosa cystica (bony cysts, Brown’s tumors)
What are the blood test findings in familial hypocalciuric hypercalcemia (FHH)? (5)
High calcium (mild)
Low phosphate
High ALP
Normal/high PTH
Low calcium in urine
What are the features of secondary hyperparathyroidism? (4)
Low calcium
High phosphate
High ALP
Low PTH
What are the effects of PTH on calcium and phosphate metabolism?
PTH increases calcium reabsorption and phosphate excretion in the kidneys. It also increases osteoclastic activity and activates 1-alpha-hydroxylase for calcium absorption.
So high PTH will cause low phosphate
What are the main causes of secondary hyperparathyroidism?
Renal osteodystrophy (renal failure) and Vitamin D deficiency.
What are the features of tertiary hyperparathyroidism? (2)
No longer sensitive to PTH, so high PTH despite high calcium
Caused by CKD leading to autonomous secretion of PTH
What are the features of Paget’s disease? (5)
Increased bone turnover
Bone pain
Bones may be warm, fractures, cardiac failure
Bowing of the tibia
Hearing loss (both conductive and sensorineural)
What are the blood test findings in Paget’s disease? (2)
Everything is normal except very raised ALP
Also get a rise in osteocalcin
What are the key investigations for Paget’s disease? (2)
X-ray
Technetium Bisphosphonate Scan (aka MDB scan): shows diffuse uptake by one bone (Paget’s) or blotchy uptake (metastatic bone cancer)
How is Paget’s disease managed? (1)
Bisphosphonates (if symptomatic)
What are the complications of lung cancer related to calcium metabolism? (2)
Produces PTHrP
Causes lytic bone lesions and raised ALP
What are the features of pseudohypoparathyroidism? (4)
PTH resistance
Associated with a short 4th & 5th metacarpal
Phenotypic picture like Albright hereditary osteodystrophy (obesity, rounded facies, hypogonadism, mild LD)
Bloods: High PTH, hypocalcaemia, high phosphate
What are the features of pseudopseudohypoparathyroidism? (4)
Normal calcium
Normal PTH
Normal biochemistry
Features of pseudohypoparathyroidism: short stature, brachydactyly, subcutaneous calcification, obesity
What are the features of primary hypoparathyroidism? (3)
Example: secondary to parathyroidectomy (or DiGeorge syndrome)
Low calcium
Low PTH and high phosphate
What are the key points about calcium in general? (5)
Important in causing depolarisation (high calcium → failure of depolarisation; low calcium → irritable nervous system)
Normal range: 2.2–2.6 mmol/L
99% stored in the bone; 1% carried in the blood
Corrected calcium (takes into account albumin) is important
Vitamin D supplements = cholecalciferol (Vitamin D3)
What are the forms of Vitamin D in humans? (2)
Cholecalciferol (Vitamin D3) from UV light
Ergocalciferol (Vitamin D2) from plants
What is the pathway for Vitamin D metabolism in the body? (5)
UV light converts 7-dehydrocholesterol in the skin to cholecalciferol (Vitamin D3)
Vitamin D3 converted to 25-hydroxycholecalciferol in the liver by 25-hydroxylase
25-hydroxycholecalciferol converted to 1,25-dihydroxycholecalciferol (calcitriol) in the kidneys by 1-alpha hydroxylase
Calcitriol increases calcium & phosphate absorption in the gut
Vitamin D levels measured in blood = levels of 25-hydroxycholecalciferol
What are the 4 main causes of hypercalcaemia? (4)
Primary hyperparathyroidism (most common)
Bone metastases (common in hospitalised patients)
Sarcoidosis (rare)
Multiple myeloma
What are other causes of hypercalcaemia? (6)
PTHrP release from cancer (e.g., small cell/squamous cell lung cancer)
Thyrotoxicosis
Hypoadrenalism
Thiazide diuretics
Excess Vitamin D
Sarcoidosis → ectopic 1-alpha hydroxylase (more common in summer; managed with high-dose prednisolone, 40 mg
What are the symptoms of hypercalcaemia? (6)
Bone: Bone pain, fractures
Stones: Kidney stones (radioopaque on imaging)
Abdominal groans: Diffuse abdominal pain, pancreatitis, constipation
Psychic moans: Depression, lethargy, confusion, seizures, coma
Polyuria, polydipsia
Nephrogenic diabetes insipidus
What are the signs of hypercalcaemia? (5)
Band keratopathy (calcium deposition across the front of the eye)
Pepperpot skull
Osteitis fibrosa cystica
NOTE: Band keratopathy develops only with chronic hypercalcaemia, commonly due to primary hyperparathyroidism
What is the management of hypercalcaemia with calcium levels between 2.6–2.8 mmol/L? (4)
No urgent treatment required
Drink lots of water
Avoid thiazide diuretics
Refer to endocrinology for minimally invasive parathyroidectomy (Sesta MIBI scan and ultrasound used to identify overactive glands)
What is the management of hypercalcaemia with calcium levels >3 mmol/L or if unwell? (5)
Administer 4–6 L of 0.9% IV saline over 24 hours (if liver failure, consider dextrose instead)
First litre should be given rapidly within 1 hour
If no room for more saline, use furosemide
Insert catheter if associated with renal failure
If malignancy + bone pain: use bisphosphonates (e.g., pamidronate)
What are the causes of hypocalcaemia? (7)
Chronic renal failure
Vitamin D deficiency
Subtotal/total thyroidectomy
Alkalosis
Acute pancreatitis
Congenital absence of parathyroids
(e.g., DiGeorge syndrome)
Magnesium deficiency (involved in PTH regulation)
What are the symptoms of hypocalcaemia? (5)
Mnemonic: CATS go NUMB
Convulsions
Arrhythmias
Tetany
Numbness (commonly around the mouth)
Other: Chvostek’s sign (facial nerve), Trousseau’s sign (carpopedal spasm), depression
How is hypocalcaemia managed? (1)
Vitamin D (may need to give activated forms in renal failure)
