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
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