Calcium, Total
para>PO4, phosphate; N, normal; I, increased; D, decreased.
TABLE 16 " 14Variations of Various Serum and Urine Analytes in Association with Hypocalcemic DisordersView LargeTABLE 16 " 14Variations of Various Serum and Urine Analytes in Association with Hypocalcemic Disorders Hypocalcemia Associated with Increased Decreased Serum PTH Pseudohypoparathyroidism Hypoparathyroidism Renal failure, acute/chronic Acute pancreatitis Malabsorption Magnesium deficiency Vitamin D deficiency Phosphate administration Serum phosphorus Hypoparathyroidism Vitamin D deficiency Pseudohypoparathyroidism Acute pancreatitis Renal failure, acute (oliguric phase)/chronic Renal failure, acute (diuretic phase) Phosphate administration Malabsorption Serum bicarbonate and pH Hypoparathyroidism Serum Mg Renal failure, acute/chronic Magnesium deficiency Acute pancreatitis Renal failure, acute (diuretic phase) Urine calcium Hypoparathyroidism Other causes of hypocalcemia Urine phosphate Renal failure, chronic Hypoparathyroidism Vitamin D deficiency Pseudohypoparathyroidism Malabsorption Magnesium deficiency Phosphate administration Urine cAMP Renal failure, chronic Hypoparathyroidism Vitamin D deficiency Pseudohypoparathyroidism Malabsorption
- Hypoparathyroidism Surgical Idiopathic infiltration of parathyroids (e.g., sarcoid, amyloid, hemochromatosis, tumor) Hereditary (e.g., DiGeorge syndrome) Pseudohypoparathyroidism Chronic renal disease with uremia and phosphate retention, Fanconi syndromes, renal tubular acidosis Malabsorption of calcium and vitamin D, obstructive jaundice Insufficient calcium, phosphorus, and vitamin D ingestion Bone disease (osteomalacia, rickets) Starvation Late pregnancy
- Altered bound calcium citrate Multiple citrated blood transfusions Dialysis with citrate anticoagulation
- Hyperphosphatemia (e.g., phosphate enema/infusion)
- Rhabdomyolysis
- Tumor lysis syndrome
- Acute severe illness (e.g., pancreatitis with extensive fat necrosis, sepsis, burns)
- Respiratory alkalosis
- Certain drugs Cancer chemotherapy drugs (e.g., cisplatin, mithramycin, cytosine arabinoside) Fluoride intoxication Antibiotics (e.g., gentamicin, pentamidine, ketoconazole) Chronic therapeutic use of anticonvulsant drugs (e.g., phenobarbital, phenytoin) Loop-active diuretics Calcitonin Gadolinium-based magnetic resonance (MR) imaging contrast agents.
- Osteoblastic tumor metastases
- Neonates born of complicated pregnancies Hyperbilirubinemia Respiratory distress, asphyxia Cerebral injuries Infants of diabetic mothers Prematurity Maternal hypoparathyroidism
- Hypermagnesemia (e.g., magnesium for treatment of toxemia of pregnancy)
- Magnesium deficiency
- Toxic shock syndrome
Temporary hypocalcemia after subtotal thyroidectomy in >40% of patients; >20% are symptomatic.
Limitations
- Total serum protein and albumin should always be measured simultaneously for proper interpretation of serum calcium levels, since 0.8 mg of calcium is bound to 1.0 g of albumin in serum; to correct, add 0.8 mg/dL for every 1.0 g/dL that serum albumin falls below 4.0 g/dL; binding to globulin only affects total calcium if globulin >6 g/dL.
- Serum levels increased by Hyperalbuminemia (e.g., multiple myeloma, Waldenstr śm macroglobulinemia) Dehydration Venous stasis during blood collection by prolonged application of tourniquet Use of cork-stoppered test tubes Hyponatremia (<120 mEq/L), which increases the protein-bound fraction of calcium, thereby slightly increasing the total calcium (opposite effect in hypernatremia)
- Serum levels decreased by Hypomagnesemia (e.g., due to cisplatin chemotherapy) Hyperphosphatemia (e.g., laxatives, phosphate enemas, chemotherapy of leukemia or lymphoma, rhabdomyolysis) Hypoalbuminemia Hemodilution