Calcium Flashcards
Calcium distribution in body
Most in bone
Small amount in serum - 50 free (active), 40 albumin bound, 10 bound to calcium / phosphate
Calcium control - 3 paths
Vitamin D + PTH
Low calcium directly stimulates PTH + indirectly stimulates vitamin D through PTH
1. Activates vitamin D (to 1,25 / calcitriol) - GUT calcium + phosphate absorption
2, KIDNEY - calcium absorption, phosphate trashing
3. BONE - calcium + phosphate release from bone
Corrected calcium
Ensures hypocalcaemia not due to low albuin
[Serum Ca + 0.02(40 - serum albumin)] or check blood gas
Normal calcium levels
2.2-2.6
Hypercalcaemia
Approach, causes, Tx
Approach: Hypercalcaemia - is PTH suppressed? (PTH should be suppressed)
Causes:
- High/ normal PTH: PTH = raised Ca (primary hyperparathyroidism - common, 80% parathyroid adenoma [high urinary calcium + stones]; OR familial hypocalciuric hypercalcaemia - rare, CaSR [low urinary calcium + no stones])
- Low PTH: Raised Ca = low PTH (malignancy - either PTHrP e.g. SCLC, bone mets (bone lysis releases - Brs), myeloma); OR non-malignant causes (loads of them e.g. sarcoid, excess vitamin D, thyrotoxicosis, adrenal failure, thiazides)
Tx - FLUIDS, FLUIDS, FLUIDS + Bisphosphonates if malignancy to stop bony pain
Hypercalcaemia symptoms
Stones, bones, abdominal moans, psychic groans, thrones
Hypercalcaemia
Raised / inapp normal PTH
Hypercalciuria + stones
Primary hyperparathyroidism (80% parathyroid adenoma)
Hypercalcaemia
Raised / inapp normal PTH
Hypocalciuria + no stones
Familial hypocalciuric hypercalcaemia
Hypocalcaemia symptoms
Neuro-muscular excitability (Trousseau’s, Chvostek’s)
- Carpopedal spasm when inflating BP cuff (Trousseau’s)
- Twitching of facial muscle when facial nerve tapped (Chvostek’s)
Perioral paraesthesia
Hypocalcaemia
Approach, causes, Tx
Approach - is PTH raised? (PTH should be raised)
Causes:
- Low PTH (low PTH = low calcium) - primary hypoparathyroidism due to surgery (thyroidectomy, AI, Di George, magnesium deficiency)
- High PTH (low calcium = high PTH) - secondary hyperparathyroidism (vitamin D deficiency, CKD) or pseudohyperparathyroidism (PTH resistance)
Tx: If mild oral calcium, if severe iv calcium; if vit D deficiency vitamin D; if CKD alfacalcidiol
CKD
Normal calcium, elevated PTH
Tertiary hyperparathyroidism
Occurs after long period of secondary hyperparathyroidism in CKD - high PTH used to be appropriate to low Ca but once Ca returns to normal no longer appt
Low Ca, raised PTH
Chappati eating, lack of sunlight, dark skin, anti-convulsant use
Looser’s zones, widened epiphysis, costchondral swelling, cupping + fraying of metaphysis
Vitamin D deficiency
Osteomalacia - Adults
Rickets - children
Tx: GIVE VITAMIN D
Looser’s zone
Pseudofractures occurring in vitamin D deficency
Normal bloods
First presentation Colle’s #
Osteoporosis
Raised ALP
Focal pain, warmth, deformity, hearing loss, frontal bossing
Paget’s disease
Secondary hyperparathyroidism
CKD
Altered bones and increased fracture risk
Renal osteodystrophy
Hyperparathyroidism
Brown tumours
Altered bones and increased fracture risk
Osteitis fibrosa cystica
Approaching a calcium / PTH question
Always look at Ca first
Look to see if PTH is appt - is Ca causing PTH or PTH causing Ca
Use algorithm to determine cause
Radio-opaque renal stones
Calcium (mixed, calcium oxalate, calcium pyruvate, triple phosphate)
Radio-lucent renal stones
Pigment (urate, cysteine)
Staghorn calculi
Triple phosphate ‘struvite’ renal stones
Hypercalcaemia of malignancy
3 causes:
- PTHrP from small cell lung cancer (acts like PTH)
- Bone metastases - Breast, Bronchus, Brostrate, Bryroid, Bridney
- Multiple Myeloma
