Summary

Vitamin D metabolism is altered in obese individuals. Our findings indicated that in patients with severe obesity, a relatively low 25(OH)D concentration was required to suppress PTH. The PTH inflection point increased following surgery-induced weight loss, highlighting 25(OH)D different regulation mechanisms in patients with obesity.

Introduction

An optimal and sufficient concentration of 25-hydroxyvitamin D (25(OH)D) has been suggested as the level required to maximally suppress intact parathyroid hormone (iPTH). We evaluated the role of surgery-induced weight loss in determining the threshold(s) of 25(OH)D required to suppress iPTH.

Methods

This study was conducted in the framework of the Tehran Obesity Treatment Study (TOTS). We prospectively analyzed 687 patients with severe obesity who participated in the TOTS and underwent bariatric surgery from March 2013 to March 2019. The patients were followed for 1 year after surgery. Anthropometric parameters and serum levels of iPTH, 25OHD, phosphorous, and calcium were measured. Nonlinear and piecewise linear regression was used to evaluate the relationship between 25(OH)D and iPTH and to determine the 25(OH)D-suppression point at which iPTH was maximally suppressed.

Results

Body mass index was 44.6 kg/m² at the baseline and decreased to 29.7 kg/m² 1 year after surgery (P < 0.05). Before the surgery, iPTH and 25(OH)D showed an exponential relationship; iPTH began to decrease rapidly at 25(OH)D concentration of 12 ng/mL, reaching maximal suppression at 30 ng/mL. However, the relationship between 25(OH)D and iPTH was non-exponential 1 year after surgery. The piecewise linear regression model revealed the 25(OH)D concentration of 21 ng/mL as the inflection point following surgery-induced weight loss.

Conclusion

In patients with severe obesity, PTH was suppressed at a relatively lower concentration of 25(OH)D; this threshold increased following surgery-induced weight loss. These findings suggest a role for bariatric surgery in regulating 25(OH)D metabolism in patients with obesity.

中文翻译：

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减肥手术在甲状旁腺激素与25-羟基维生素D代谢关系中的中介作用

概括

肥胖个体的维生素 D 代谢发生改变。我们的研究结果表明，在严重肥胖的患者中，需要相对较低的 25(OH)D 浓度来抑制 PTH。手术引起的体重减轻后 PTH 拐点增加，突出了 25(OH)D 在肥胖患者中的不同调节机制。

介绍

已建议将 25-羟基维生素 D (25(OH)D) 的最佳和足够浓度作为最大限度抑制完整甲状旁腺激素 (iPTH) 所需的水平。我们评估了手术引起的体重减轻在确定抑制 iPTH 所需的 25(OH)D 阈值中的作用。

方法

这项研究是在德黑兰肥胖治疗研究 (TOTS) 的框架内进行的。我们前瞻性分析了 2013 年 3 月至 2019 年 3 月参加 TOTS 并接受减肥手术的 687 名重度肥胖患者。患者术后随访 1 年。测量了人体测量参数和 iPTH、25OHD、磷和钙的血清水平。非线性和分段线性回归用于评估 25(OH)D 和 iPTH 之间的关系，并确定最大程度抑制 iPTH 的 25(OH)D 抑制点。

结果

体重指数基线为44.6 kg/m ² ，术后1年降至29.7 kg/m ^{2 (} P  < 0.05)。术前iPTH与25(OH)D呈指数关系；iPTH 在 25(OH)D 浓度为 12 ng/mL 时开始迅速下降，在 30 ng/mL 时达到最大抑制。然而，25(OH)D 与 iPTH 之间的关系在术后 1 年呈非指数关系。分段线性回归模型显示 25(OH)D 浓度为 21 ng/mL 作为手术引起的体重减轻后的拐点。

结论

在严重肥胖的患者中，PTH 在相对较低的 25(OH)D 浓度下受到抑制；这个阈值在手术引起的体重减轻后增加。这些发现表明减肥手术在调节肥胖患者的 25(OH)D 代谢中的作用。