Typical Laboratory Test Results in Some Disorders Causing Hypocalcemia
Disorder | Findings |
|---|---|
Idiopathic hypoparathyroidism | High serum PO4 Low urinary PO4 Normal serum alkaline phosphatase Undetectable PTH |
Surgical hypoparathyroidism | Low or low-normal PTH Normal or high serum PO4 Low urinary PO4 Normal serum alkaline phosphatase |
Type I hereditary vitamin D–dependent rickets | High PTH Low serum PO4 High alkaline phosphatase X-ray evidence of rickets Normal serum 25(OH)D Low serum 1,25(OH)2D |
Type II hereditary vitamin D–dependent rickets | High PTH Low serum PO4 High alkaline phosphatase X-ray evidence of rickets Normal or high serum 25(OH)D Normal or high 1,25(OH)2D |
Type Ia pseudohypoparathyroidism (Albright hereditary osteodystrophy) | High PTH High serum PO4 No urinary cAMP or increase in PO4 excretion even after injection of PTH or a PTH analog Skeletal and other abnormalities |
Type Ib pseudohypoparathyroidism | High PTH High serum PO4 No urinary cAMP or increase in PO4 excretion even after injection of PTH or a PTH analog No skeletal abnormalities |
Type II pseudohypoparathyroidism | High PTH High serum PO4 No urinary cAMP or PO4 Injection of PTH increases urinary cAMP but not urinary PO4 Normal or high vitamin D concentrations |
Vitamin D deficiency | High PTH Low serum PO4 High alkaline phosphatase Low 25(OH)D* |
* Measurement of serum 25(OH)D and 1,25(OH)2D may help distinguish vitamin D deficiency from vitamin D–dependent states. | |
1,25(OH)2D = 1,25-dihydroxycholecalciferol or calcitriol; 25(OH)D = inactive vitamin D; cAMP = cyclic adenosine monophosphate; PO4 = phosphate; PTH =parathyroid hormone. | |