Table 1.

Pertinent laboratory investigations in the index patienta

ParameterPresentation with TetanyFollow-up 4 Mo LaterNormal Range
Plasma indices
    magnesium (mg/dl [mM])1.58 (0.620)b1.22 (0.500)b1.58 to 2.43 (0.650 to 1.000)
    total calcium (mg/dl [mM])5.20 (1.300)b9.20 (2.310)8.80 to 10.65 (2.190 to 2.660)
    phosphate (mg/dl [mM])7.53 (2.430)b4.34 (1.400)3.40 to 5.40 (1.100 to 1.750)
    creatinine (mg/dl [mM])0.55 (0.049)0.81 (0.072)0.40 to 0.90 (0.035 to 0.080)
    albumin (g/L)454937 to 56
PTH (ng/L [pM])176 (19.0)b55 (5.8)10 to 65 (0.7 to 5.6)
25-hydroxyvitamin D (nM)25Not obtained15 to 100
Urinary indices
    magnesium (mg/dl [mM])Not obtained6.08 (2.50)
    FEMg (%)Not obtained9.5b<4c
    calcium (mg/dl [mM])Not obtained<1 (<0.25)
    FECa (%)Not obtained<0.2>1c
    creatinine (mg/dl [mM])Not obtained43 (3.80)
  • a Selected laboratory investigations at presentation of the index case and at follow-up 4 mo later. Note the hypocalcaemia and hypomagnesemia at presentation. While the plasma calcium normalized with time, magnesium remained low.

  • b Abnormal value.

  • c No clearly defined normal values exist because urinary calcium and magnesium excretion reflects dietary intake in steady state; however, in the presence of hypomagnesemia, FEMg >4% is considered pathologic hypermagnesuria and hypocalciuria is usually defined as FECa <1% (see the Concise Methods section).