Parathyroid hormone is a plausible mediator for the metabolic syndrome in the morbidly obese: a cross-sectional studyReport as inadecuate

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Cardiovascular Diabetology

, 10:17

First Online: 10 February 2011Received: 29 November 2010Accepted: 10 February 2011


BackgroundThe biological mechanisms in the association between the metabolic syndrome MS and various biomarkers, such as 25-hydroxyvitamin D vit D and magnesium, are not fully understood. Several of the proposed predictors of MS are also possible predictors of parathyroid hormone PTH. We aimed to explore whether PTH is a possible mediator between MS and various possible explanatory variables in morbidly obese patients.

MethodsFasting serum levels of PTH, vit D and magnesium were assessed in a cross-sectional study of 1,017 consecutive morbidly obese patients 68% women. Dependencies between MS and a total of seven possible explanatory variables as suggested in the literature, including PTH, vit D and magnesium, were specified in a path diagram, including both direct and indirect effects. Possible gender differences were also included. Effects were estimated using Bayesian path analysis, a multivariable regression technique, and expressed using standardized regression coefficients.

ResultsSixty-eight percent of the patients had MS. In addition to type 2 diabetes and age, both PTH and serum phosphate had significant direct effects on MS; 0.36 95% Credibility Interval CrI 0.15, 0.57 and 0.28 95% CrI 0.10,0.47, respectively. However, due to significant gender differences, an increase in either PTH or phosphate corresponded to an increased OR for MS in women only. All proposed predictors of MS had significant direct effects on PTH, with vit D and phosphate the strongest; -0.27 95% CrI -0.33,-0.21 and -0.26 95% CrI -0.32,-0.20, respectively. Though neither vit D nor magnesium had significant direct effects on MS, for women they both affected MS indirectly, due to the strong direct effect of PTH on MS. For phosphate, the indirect effect on MS, mediated through serum calcium and PTH, had opposite sign than the direct effect, resulting in the total effect on MS being somewhat attenuated compared to the direct effect only.

ConclusionOur results indicate that for women PTH is a plausible mediator in the association between MS and a range of explanatory variables, including vit D, magnesium and phosphate.

Electronic supplementary materialThe online version of this article doi:10.1186-1475-2840-10-17 contains supplementary material, which is available to authorized users.

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Author: Jo Røislien - Ben Van Calster - Jøran Hjelmesæth


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