Endocr Pract. 2020 Feb;26(2):174-178. doi: 10.4158/EP-2019-0325. Epub 2019 Sep 26.
Normocalcemic primary hyperparathyroidism (NPHPT) is characterized by elevated parathyroid hormone (PTH) levels with persistently normal calcium levels. The diagnosis of NPHPT assumes the absence of secondary causes of elevated PTH levels. The objective of the current study was to examine levels of free 25-hydroxyvitamin D (25[OH]D) in NPHPT subjects and healthy controls. Ten NPHPT subjects and 20 controls who were age, sex, race, and body mass index (BMI) matched were examined. The diagnosis of NPHPT was made if subjects had () a serum calcium level of 8.6 to 10.4 mg/dL, total 25(OH)D 30 to 40 ng/mL, and intact PTH (iPTH) ≥66 pg/mL; and () normal renal and liver function. Serum total 25(OH)D levels were measured by radioimmunoassay, and free 25(OH)D levels were determined using an enzyme-linked immunoassay. Mean age of NPHPT subjects was 59.9 ± 5.4 years, and mean BMI was 28.4 ± 2.3 kg/m, which was not significantly different from the mean age and BMI of the control subjects. Mean total 25(OH)D level was 31.9 ± 1.7 ng/mL in NPHPT subjects and did not differ from that of the controls (32.7 ± 3.3 ng/mL; = .52). However, mean free 25(OH)D was 5.0 ± 0.9 pg/mL in NPHPT subjects, which was 20% lower compared to the mean of the controls (6.2 ± 1.3 pg/mL; = .013). Serum iPTH levels were inversely correlated with levels of measured free 25(OH)D ( = -0.42; <.05) but did not correlate with levels of total 25(OH)D ( = -0.14; >.10). Measured free 25(OH)D levels are lower in NPHPT subjects than in healthy control subjects. We suggest that some NPHPT subjects may actually have secondary hyperparathyroidism based on their free 25(OH) D levels. = 25-hydroxyvitamin D; = body mass index; = coefficient of variation; = vitamin D-binding protein; = intact parathyroid hormone; = normocalcemic primary hyperparathyroidism.
血钙正常型原发性甲状旁腺功能亢进症（NPHPT）的特点是甲状旁腺激素（PTH）水平升高，而血钙水平持续正常。NPHPT 的诊断假设不存在升高的 PTH 水平的继发性原因。本研究的目的是检查 NPHPT 患者和健康对照者的游离 25-羟维生素 D（25[OH]D）水平。检查了 10 名 NPHPT 患者和 20 名年龄、性别、种族和体重指数（BMI）匹配的对照者。如果患者（）血清钙水平为 8.6 至 10.4mg/dL，总 25（OH）D30 至 40ng/mL，完整的 PTH（iPTH）≥66pg/mL；和（）正常的肾功能和肝功能，则可诊断为 NPHPT。血清总 25（OH）D 水平通过放射免疫测定法测量，游离 25（OH）D 水平通过酶联免疫吸附测定法测定。NPHPT 患者的平均年龄为 59.9±5.4 岁，平均 BMI 为 28.4±2.3kg/m，与对照组的平均年龄和 BMI 无显著差异。NPHPT 患者的平均总 25（OH）D 水平为 31.9±1.7ng/mL，与对照组无差异（32.7±3.3ng/mL；=0.52）。然而，NPHPT 患者的平均游离 25（OH）D 为 5.0±0.9pg/mL，比对照组的平均值低 20%（6.2±1.3pg/mL；=0.013）。血清 iPTH 水平与测定的游离 25（OH）D 水平呈负相关（=0.42；<0.05），但与总 25（OH）D 水平不相关（=0.14；>0.10）。与健康对照组相比，NPHPT 患者的游离 25（OH）D 水平较低。我们认为，根据游离 25（OH）D 水平，一些 NPHPT 患者实际上可能患有继发性甲状旁腺功能亢进症。25-羟维生素 D；体重指数；变异系数；维生素 D 结合蛋白；完整的甲状旁腺激素；血钙正常型原发性甲状旁腺功能亢进症。
