Differentials
Hypomagnesemia
SIGNS / SYMPTOMS
Symptoms may be out of proportion to the degree of hypocalcemia.
INVESTIGATIONS
Low serum magnesium.
Normal or low serum calcium.
Hypoalbuminemia
SIGNS / SYMPTOMS
This is likely asymptomatic. A medical condition causing low albumin production or increased losses may be present, e.g., nephrotic syndrome, cirrhosis, anasarca.
INVESTIGATIONS
Low serum albumin.
Normal albumin-corrected serum total calcium or ionized calcium.
Chronic kidney disease
SIGNS / SYMPTOMS
Other symptoms of uremia may be present, e.g., low urine volume, pruritus, altered mental status, volume overload.
INVESTIGATIONS
Elevated serum creatinine.
Elevated plasma intact PTH level.
Vitamin D deficiency
SIGNS / SYMPTOMS
Diet is deficient in foods containing vitamin D, sunlight exposure is limited.
Malabsorption, short bowel, diarrhea, gastric bypass, or any other mechanism leading to fat-soluble vitamin deficiency is present.
INVESTIGATIONS
Plasma intact parathyroid hormone (PTH) level is low or inappropriately normal in hypoparathyroidism, and elevated in vitamin D deficiency.
Serum 25-hydroxyvitamin D <20 nanograms/mL (<50 nanomol/L) in vitamin D deficiency, and usually <10 nanograms/mL (<25 nanomol/L) if hypocalcemia is present and vitamin D deficiency is chronic and moderate to severe.
Pseudohypoparathyroidism
SIGNS / SYMPTOMS
Albright hereditary osteodystrophy may be present, e.g., short stature, reduced intelligence, brachydactyly, frontal bossing, obesity.
INVESTIGATIONS
Elevated plasma intact PTH level.
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