Hypoparathyroidism

Background

• Parathyroid hormone (PTH) increases osteolysis, renal tubular resorption of calcium, and renal synthesis of 1,25-dihydroxycholecalciferol AND inhibits renal tubular reabsorption of phosphate and bicarbonate, leading to net INCREASE in serum calcium
• Hypoparathyroid thus results in hypocalcemia with hyperphosphatemia

Causes

• Iatrogenic:
  • Anterior neck surgery or radiation (e.g. resection of multiple parathyroid adenomas, thyroidectomy); may be transient
  • steroids, diuretics, antiepilptics
• Congenital (e.g. DiGeorge syndrome)
• Malignancy
• Autoimmune
• Damage from Heavy metals (e.g. copper in Wilson's disease)
• Functional hypoPTH from hypomagnesemia

Clinical Features

• See Hypocalcemia, hyperphosphatemia

Differential Diagnosis

• Vitamin D deficiency
• Pseudohypoparathyroidism (renal resistance to PTH)
• Kidney disease
• Malabsorption
• Iatrogenic:
  • Anterior neck surgery or radiation (e.g. resection of multiple parathyroid adenomas, thyroidectomy); may be transient
  • steroids, diuretics, antiepilptics
• Congenital (e.g. DiGeorge syndrome)
• Malignancy
• Autoimmune
• Damage from Heavy metals (e.g. copper in Wilson's disease)
• Functional hypoPTH from hypomagnesemia

Evaluation

• CMP
  • Low serum calcium
  • Normal alk phos
• PTH (low or inappropriately normal in setting of hypocalcemia)
• EKG
• Magnesium levels
• Phosphate levels (high)

Management

• Treat underlying condition

Hypocalcemia

Avoid empiric treatment in patients taking digoxin due to risk for Stone Heart

• Asymptomatic
  • Calcium gluconate 1 gm PO Q6hrs
  • Vitamin D (calcitriol) 0.2 mcg BID
• Symptomatic
  • Calcium gluconate/chloride 10mL of 10% soln IV over 10min
• Correct hypomag at same time (otherwise PTH is inhibited)
• Avoid phenothiazine antipsychotics (may precipitate extrapyramidal symptoms)
• Avoid furosemide (may worsen hypocalcemia)

Disposition

• Admit if symptomatic hypocalcemia

See Also

• Hypocalcemia, hyperphosphatemia
• Electrolyte Abnormalities (Main)