Aloia John, Dhaliwal Ruban, Mikhail Mageda, Shieh Albert, Stolberg Alexandra, Ragolia Louis, Fazzari Melissa, Abrams Steven A
Winthrop University Hospital, Mineola, New York 11501.
J Clin Endocrinol Metab. 2015 Nov;100(11):4140-5. doi: 10.1210/jc.2015-2548. Epub 2015 Aug 27.
It has been proposed that serum free 25-hydroxyvitamin D [25(OH)D] may better reflect vitamin D action than total 25(OH)D. An ELISA for serum free 25(OH)D has recently become available, permitting direct assay.
To determine whether serum free 25(OH)D provides additional information in relation to calcium absorption and other biomarkers of vitamin D action compared to total serum 25(OH)D.
Ambulatory research setting in a teaching hospital.
Serum free 25(OH)D measured in a previously performed study of varied doses of vitamin D3 (placebo and 800, 2000, and 4000 IU) on calcium absorption, PTH, procollagen type 1 N-terminal propeptide, and C-terminal telopeptides of type I collagen. Free 25(OH)D was measured by ELISA. Calcium absorption was measured at baseline and at 10 weeks using stable dual calcium isotopes.
Seventy-one subjects completed this randomized, placebo-controlled trial. Baseline group mean free and total 25(OH)D varied from 4.7 ± 1.8 to 5.4 ± 1.5 pg/mL, and from 23.7 ± 5.9 to 25.9 ± 6.1 ng/mL, respectively. Participants assigned to the 4000-IU dose arm achieved free 25(OH)D levels of 10.4 pg/mL and total 25(OH)D levels of 40.4 ng/mL. Total and free 25(OH)D were highly correlated at baseline and after increasing vitamin D dosing (r = 0.80 and 0.85, respectively). Free 25(OH)D closely reflected changes in total 25(OH)D. PTH was similarly correlated at baseline and follow-up with total and free 25(OH)D. Serum C-terminal telopeptides of type I collagen had a moderate positive correlation with total and free 25(OH)D at follow-up. The serum 1,25-dihydroxyvitamin D change increased significantly with the change in 25(OH)D but not with the change in free 25(OH)D.
There was no advantage from measuring free over total 25(OH)D in assessing the response of calcium absorption, PTH, and markers of bone turnover to vitamin D. Free 25(OH)D responded to increasing doses of vitamin D in a similar fashion to total 25(OH)D.
有人提出，血清游离25-羟基维生素D[25(OH)D]可能比总25(OH)D能更好地反映维生素D的作用。一种用于血清游离25(OH)D的酶联免疫吸附测定（ELISA）最近已可用于直接检测。
确定与总血清25(OH)D相比，血清游离25(OH)D在钙吸收及维生素D作用的其他生物标志物方面是否能提供更多信息。
一家教学医院的门诊研究机构。
在一项先前进行的关于不同剂量维生素D3（安慰剂、800、2000和4000国际单位）对钙吸收、甲状旁腺激素（PTH）、1型前胶原N端前肽及1型胶原C端肽的影响的研究中，检测了血清游离25(OH)D。游离25(OH)D通过ELISA测定。使用稳定的双钙同位素在基线和10周时测量钙吸收。
71名受试者完成了这项随机、安慰剂对照试验。基线时，各组游离和总25(OH)D的平均水平分别为4.7±1.8至5.4±1.5皮克/毫升和23.7±5.9至25.9±6.1纳克/毫升。分配到4000国际单位剂量组的参与者游离25(OH)D水平达到10.4皮克/毫升，总25(OH)D水平达到40.4纳克/毫升。在基线和增加维生素D剂量后，总25(OH)D与游离25(OH)D高度相关（分别为r = 0.80和0.85）。游离25(OH)D密切反映了总25(OH)D的变化。PTH在基线和随访时与总25(OH)D和游离25(OH)D的相关性相似。随访时，血清1型胶原C端肽与总25(OH)D和游离25(OH)D呈中度正相关。血清1,25-二羟基维生素D的变化随25(OH)D的变化显著增加，但不随游离25(OH)D的变化增加。
在评估钙吸收、PTH及骨转换标志物对维生素D的反应时，测量游离25(OH)D相对于总25(OH)D并无优势。游离25(OH)D对维生素D剂量增加的反应与总25(OH)D相似。
