disorders of calcium homeostasis part 2 W2 Flashcards
what causes the symptoms of hypocalcaemia
increase in neuromuscular excitability due to increased inward Na+ movement.
resting potential of membrane is increased in hypocalcaemia
action potentials may be spontaneously generated
neuromuscular clinical manifestations of hypocalcaemia?
numbness and paraesthesia (tingling) in fingertips, toes, around mouth
anxiety and fatigue
muscle cramps, carpo-pedal spasm, bronchial or laryngeal spasm
seizures
clinical manifestations of hypocalcaemia - mental state?
personality change
confusion, psychoneurosis
impaired intellectual ability
clinical manifestations of hypocalcaemia other than neuromuscular and mental state
ECG changes (prolongation of QT interval) - can lead to cardiac arrest
eye problems - cloudiness
Chvostek’s sign?
contraction of muscles of eyes/mouth/nose elicited by tapping along the course of the facial nerve (in front of ear)
neurological signs of hypocalcaemia?
Chvostek’s sign
Trousseau’s sign
Trousseau’s sign
bp cuff used, brachial artery occluded for 3 minutes.
causes involuntary spasm of muscles resulting in adducted thumb, grouped fingers, flexed wrist
factitious hypocalcaemia causes?
consequence of low plasma albumen
-acute phase response
-malnutrition/malabsorption
-liver disease
-nephrotic syndrome
common cause of hypocalcaemia
vitamin D deficiency!! caused by
lack of sunlight exposure
inadequate dietary source
malabsorption
chronic renal disease (common)
chronic liver disease (rare)
rare genetic causes
vitamin D deficiency risk factors?
those confined indoors (esp elderly)
dark skin
high latitudes
lack of sunlight exposure (via dress, suncream, etc)
biochemical features of vitamin D deficiency
low 25-D3 and 1,25-D3 (
low Ca2+
high PTH
phosphate tends to be low
often raised ALP
clinical features of vitamin D deficiency
symptoms related to low Ca2+
osteomalacia (bone pain, fractures disordered growth in children as a consequence of defective mineralisation)
what is osteomalacia called in children?
Rickets
osteomalacia pathophysiology?
pathological bone problem classically associated with vitamin D deficiency
osteoid laid down by osteoblasts is not adequately calcified
osteoid content in bone increases as expense of normal calcified osteoid (bone matrix)
bones are softened, weak and susceptible to fracture
inherited causes of osteomalacia/rickets?
deficient 1-hydroxylase (vitamin D-resistant rickets type 1)
defective receptor for calcitriol (vitamin D-resistant rickets type 2)
hypoparathyroidism causes
acquired
-surgical damage/removal
-suppressed secretion
inherited
-developmental parathyroid problems
-genetic/familial disorders
hypoparathyroidism biochemistry?
low Ca2+
inappropriately low PTH
phosphate may be increased
what is magnesium required for
required for PTH action
what can cause suppressed secretion in acquired hypoparathyroidism
low magnesium
maternal hypercalcaemia
treatment of hypocalcaemia
acute - IV calcium
normally oral calcium and vitamin D are given (sometimes Mg)
vitamin D given in various forms
-by injection if malabsorption
-as 10H form if renal function
impaired
close monitoring of plasma calcium concentration necessary
osteoporosis features
reduced bone mineral density, disruption of microarchitecture
routine biochemistry unaffected
osteoporosis vs osteomalacia in terms of biochemistry
osteoporosis - normal biochem
osteomalacia - abnormal biochem