Calcium is the most abundant cation in the body. The total serum calcium level is the sum of ionized calcium plus complexed calcium and protein-bound calcium.
99% of calcium in the body is in the bones and teeth with the other 1% in circulation. Calcium serves critical functions in nerve conduction, muscle contractility & relaxation, hormone secretion, and blood coagulation.
Hypocalcemia (low Calcium) can clinically present with:
- Cardiac arrhythmias
- Changes in ECG
- Prolonged ST segment
- Prolonged Q-T interval
- Facial spasms (positive Chvostek's sign)
- Muscle cramps
- Muscle twitching (positive Trousseau's sign)
- Numbness in the extremities
- Seizures
- Tetany
- Tingling sensation
Hypercalcemia (high Calcium) can clinically present with:
The total serum calcium level is clinically useful in:
- Evaluating disorders of calcium metabolism
- Detecting the loss of parathyroid gland function after thyroid or other neck surgery (indicated by decreased levels)
- Detecting hyperparathyroidism
- Evaluating cardiac arrhythmias and coagulation disorders (to check if an altered serum calcium level is a contributing factor)
- Monitoring therapy to correct abnormal calcium levels
- Monitoring effects of drugs that alter the calcium levels
Additional information:
- The concentration of calcium is mainly regulated by parathyroid hormone and vitamin D
- Calcium levels are higher in children because of growth and active bone formation
- Calcium levels are inversely proportional to the phosphorus levels
- There is a 1-3% day-to-day variation in a particular individual
- The level is highest at 8 P.M. and lowest at 4 A.M. and lowest in winter and highest in summer
- Coma may occur at serum calcium levels >13 mg/dL
- The effects of hypercalcemia may be intensified by acidosis
Consult your laboratory for their normal ranges as these may vary somewhat from the ones listed below.
The serum calcium must be corrected for the blood albumin level. Every decrease in albumin by 1 g/dL (from a value of 4.0 g/dL) requires an adjustment factor of adding 0.8 mg/dL (0.2 mmol/L) to the measure serum calcium. The same correction factor is required for increased albumin levels.
| Conv. Units
(mg/dL) | SI Units
(mmol/L) |
|---|
| Adult | 8.2-10.6 | 2.05-2.65 |
| Children | 8.6-11.2 | 2.15-2.80 |
| Infant | 7.8-11.2 | 1.95-2.80 |
| Newborn | 7.0-12.0 | 1.75-3.00 |
| Critical Values | <6.5 | <1.63 |
| >13 | >3.25 |
Hypercalcemia is the term for elevated blood calcium level. It may be seen in the following conditions:
- Based on the parathyroid status:
- Increased PTH
- Aluminum Bone Disease
- Drugs as listed below
- Familial hypocalciuric hypercalcemia
- Primary Hyperparathyroidism
- Adenoma
- Carcinoma
- Hyperplasia (including MEN types 1, 2a)
- Secondary Hyperparathyroidism
- Renal osteodystrophy after successful renal transplant
- Vitamin D deficiency
- Tertiary Hyperparathyroidism
- Others:
- Neck radiation
- Pheochromocytoma
- Decreased or Normal PTH
- Malignancy
- Other endocrine disorders
- Granulomatous disorders
- Hypercalcemia of infancy
- Iatrogenic
- Hypervitaminosis A
- Hypervitaminosis D
- Milk alkali syndrome (Burnett's syndrome)
- Some drugs as listed below
- Total parenteral nutrition
- Immobilization (prolonged)
- Rhabdomyolysis
- Rheumatoid arthritis
- Tumors associated with hypercalcemia:
- Adenocarcinoma of lungs
- Breast
- Cancers of the bone
- Chondrosarcoma
- Large cell anaplastic of lungs
- Leukemia
- Lower genitourinary tract cancer
- Malignant lymphoma
- Melanoma
- Multiple myeloma
- Prostate carcinoma
- Renal carcinoma
- Squamous cell carcinoma
- Lungs
- Head and neck
- Esophagus
- Cervix
- Thyroid carcinoma
- Drug-induced hypercalcemia
- Familial benign hypercalcemia
- Others
- Dehydration
- Excess intake of milk
- Hypocalciuria
- Multiple fractures
- Paget's disease
- Polycythemia vera
Drugs that may increase the calcium levels include:
- Lithium
- Tamoxifen
- Theophylline
- Thiazides
Hypocalcemia is the term for decreased blood calcium level. It may be seen in the following conditions:
- Based on parathyroid status
- Decreased PTH
- Autoimmune hypoparathyroidism
- DiGeorge Syndrome
- Iatrogenic
- Infiltrative
- Magnesium deficiency (End-organ resistance)
- Metastatic cancer
- Neonatal period (transient)
- Postsurgical
- Prematurity
- Normal or increased PTH
- Familial Syndrome of hypocalcemia with hypercalciuria
- "Hungry bones"
- Post-parathyroidectomy
- Post renal transplant in renal osteodystrophy
- Post-thyroidectomy
- Post-vitamin D replacement in rickets
- Increased osteoblastic activity
- Decreased osteoclastic activity
- Medullary carcinoma of thyroid
- Drugs as listed below
- Rhabdomyolysis
- Liver disease
- Pseudohypoparathyroidism Types 1a, 1b, 1c, 2
- Renal failure
- Vitamin D deficiency
- Hyperphosphatemia and hypocalcemia
- Hypoparathyroidism
- Pseudohypoparathyroidism
- Renal failure
- Others
- Acute pancreatitis
- Alcoholism
- Alkalosis
- Cystinosis
- Hypoalbuminemia
- Inadequate nutrition
- Leprosy
- Malabsorption
- Massive blood transfusion (due to presence of citrates)
- Osteomalacia
- Peritonitis
Drugs that may cause hypocalcemia include: