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Abstract：
Although clinical guidelines recommend measuring total plasma 25-hydroxyvitamin D (25[OH]D) to assess vitamin D (VitD) status, this index does not account for 3-fold inter-individual variation in VitD binding protein (VDBP) level. We present 3 individuals with total plasma 25(OH)D levels of 10.8 to 12.3 ng/mL (27-30.7 nmol/L). Because Endocrine Society guidelines define VitD deficiency as 25(OH)D ≤ 20 ng/mL (50 nmol/L), all 3 would be judged to be VitD deficient. VitD3 supplementation increased 25(OH)D to the range of 31.7 to 33.8 ng/mL (79.1-84.4 nmol/L). Patient #1 exhibited secondary hyperparathyroidism; VitD3 supplementation decreased parathyroid hormone (PTH) by 34% without a clinically significant change in PTH levels in the other 2 individuals. Thus, 25(OH)D level did not distinguish between the 1 patient who had secondary hyperparathyroidism and the 2 who did not. We therefore inquired whether VitD metabolite ratios (which are VDBP-independent) might distinguish among these 3 individuals. Of all the assessed ratios, the 1,25(OH)2D/24,25(OH)2D ratio was the most informative, which had a value of 102 pg/ng in the individual with secondary hyperparathyroidism but lower values (41 and 20 pg/ng) in the other 2 individuals. These cases illustrate the value of the 1,25(OH)2D/24,25(OH)2D ratio to provide clinically relevant information about VitD status.
摘要：
尽管临床指南建议测量血浆总25-羟基维生素D（25[OH]D）以评估维生素D（VitD）状态，该指数不考虑VitD结合蛋白（VDBP）水平的3倍个体间差异。我们提供了3名总血浆25（OH）D水平为10.8至12.3ng/mL（27-30.7nmol/L）的个体。由于内分泌学会指南将VitD缺乏症定义为25（OH）D≤20ng/mL（50nmol/L），所有3个将被判断为VitD缺乏。补充VitD3可将25（OH）D增加到31.7至33.8ng/mL（79.1-84.4nmol/L）。患者#1表现出继发性甲状旁腺功能亢进;VitD3补充使甲状旁腺激素(PTH)降低34%,而在其他2个个体中PTH水平无临床显著变化。因此，25（OH）D水平无法区分1例继发性甲状旁腺功能亢进患者和2例未发生继发性甲状旁腺功能亢进患者。因此，我们询问VitD代谢物比率（不依赖VDBP）是否可以在这3个个体中进行区分。在所有评估的比率中，1,25(OH)2D/24,25(OH)2D比率是信息最丰富的，在继发性甲状旁腺功能亢进的个体中，该值为102pg/ng，但在其他2个个体中，该值较低（41和20pg/ng）。这些病例说明了1,25(OH)2D/24,25(OH)2D比率的值,以提供关于VitD状态的临床相关信息。
