parathyroid disorders

PTH
1. ++ bone formation via osteoblasts (bone forming cells)
2. when Ca2+ levels low
  1. ++ bone resorption via osteclasts
  2. ++ renal uptake of Ca2+
  3. activate vit D metabolism
    1. ++ gut absorption of Ca2+
hypoparathyroidism
1. rare in childhood
2. low serum Ca2+
  1. Rx
    1. of symptomatic hypocalcaemia
      1. iv 10% calcium gluconate solution
        must be dilated
        else extravasation of infusion-> severe skin damage
    2. chronic hypocalcaemia
      1. oral Ca2+
      2. high dose vit D analogues
        adjust dose to keep plasma [Ca2+] just under normal range
        avoid hypercalciuria
        can cause nephrocalcinosis
        so monitor urinary Ca2+ excretion
3. PTH very low
4. raised serum phosphate
5. normal alkaline phosphate
6. if severe ->
  1. muscle spasm
  2. fits
  3. stridor
  4. diarrhoea
7. common in premature infants
8. can be a presentation of severe rickets
  1. other causes rare in childhood
9. causes in infants
  1. congenital deficiency
    1. DiGeorge syn
      1. thymic aplasia
      2. defective immunity
      3. cardiac defects
      4. facial abnormalities
10. in older children
  1. autoimmune disorder
    1. associated w/ Addison disease
pseudohypoparathyroidism
1. end organ resistance to action of PTH
  1. due to mutation in a signalling molecule
2. normal or high PTH
3. abnormal Ca2+ & phosphate levels (low?)
4. clinical features
  1. short stature
  2. obesity
  3. subcutaneous nodules
  4. short 4th metacarpals
  5. learning difficulties
  6. teeth enamel hypoplasia
  7. calcification of basal ganglia
  8. pseudopseudoparathyroidism
    1. PTH, Ca2+, phosphate all normal
    2. similar physical features to pseudoparathyroidism
  9. +ve fam hx of pseudohypo and pseudopseudohypo in same kindred
hyperparathyroidism
1. -> high Ca2+ level->
  1. constipation
  2. anorexia
  3. lethargy
  4. behavioural effects
  5. polyuria
  6. polydipsia
2. wrist radiograph
  1. bony erosions of phalanges
3. neonates & young kids
  1. assoc w/ rare genetic abnormalities
    1. e.g. William syn
4. later childhood
  1. secondary to spontaneously occurring adenomas
  2. part of multiple endocrine neoplasia (MEN) syndromes
5. Rx of severe hypercalcaemia
  1. rehydration
  2. diuretics
  3. bisphosphonates

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parathyroid disorders

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	Created by v.djabatey over 10 years ago