Abstract
An adolescent boy with pseudohypoparathyroidism was treated with massive doses of vitamin D2 (D2) and oral calcium for 8 years. At age 13 he had a convulsive episode due to severe hypocalcemia (serum calcium 5.8mg/dl). Serum 25-OH vitamin D (25-OHD) concentration was high, (40ng/ml) but much lower than his “usual” therapeutic levels which varied between 300 and 600ng/ml. The patient and his parents denied any lack of compliance. Manufacturing error was excluded by measuring D2 concentration in the D2 preparation taken, and malabsorption of lipid-soluble nutrients was ruled out by normal serum levels of vitamin A, E, and carotene. Differential analysis of D2, D3, 25-OH D2 and 25-OH D3 showed: a normal serum concentration of D3 and of 25-OH D3 while D2 and 25-OH D2 concentrations were slightly above the normal range. Normal 25-OH D3 levels indicated a normal hepatic 25-hydroxylation; on the other hand, a low 25-OH D3 serum concentration was expected in this patient receiving massive doses of D2, due to preferential binding of D3 to serum D-binding-protein, wnich allows more “free” D2 to be available for 25-hydroxylation. Non-compliance with treatment was demonstrated, and the patient admitted not having taken his medication for a month. Differential analysis of D metabolites allowed direct assessement of compliance with vitamin D2 therapy in this patient.
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Mimouni, F., Neumann, V., Tsang, R. et al. 471 DIFFERENTIAL MEASUREMENT OF VITAMIN D2 AND D3, METABOLITES: ASSESSMENT OF COMPLIANCE WITH VITAMIN D2THERAPY. Pediatr Res 19, 189 (1985). https://doi.org/10.1203/00006450-198504000-00501
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DOI: https://doi.org/10.1203/00006450-198504000-00501