|dc.description.abstract||Background: The prevalence of vitamin D insufficiency and secondary hyperparathyroidism is high among morbidly obese
subjects. Further, low serum levels of 25-hydroxyvitamin D (25 [OH]D) and magnesium have been associated with increased
risk of the metabolic syndrome (MS), and recently, a possible link between PTH and MS has been reported. Although it is well
known that the synthesis and secretion of PTH is regulated by serum levels of calcium, phosphate, magnesium and 25(OH)D,
less is known about the possible clustered affiliation of these parameters with MS. We aimed to explore whether MS is
associated with abnormal serum levels of PTH, 25(OH)D and magnesium in a population of morbidly obese patients.
Methods: Fasting serum levels of 25(OH)D, PTH and magnesium were assessed in a cross-sectional cohort study of 1,017
consecutive morbidly obese patients (68% women). Multiple logistic regression analyses were used to assess the independent
effect of PTH, 25(OH)D and magnesium on the odds for MS (National Cholesterol Education Program [NCEP]) after adjustment
for confounding factors.
Results: Sixty-eight percent of the patients had MS. Patients with MS had lower mean serum magnesium (P < 0.001) and higher
mean PTH (P = 0.067) than patients without MS, whereas mean 25(OH)D did not differ significantly. Patients with PTH levels
in the second to fourth quartiles had higher odds of prevalent MS (odds ratio 1.47 [95% CI 0.92–2.35], 2.33 [95% CI 1.40–3.87]
and 2.09 [95% CI 1.23–3.56], respectively), after adjustment for 25(OH)D, magnesium, calcium, phosphate, creatinine, age,
gender, season of serum sampling, BMI, current smoking, albuminuria, CRP, insulin resistance and type 2 diabetes. Further, PTH
was significantly correlated with systolic and diastolic pressure (both P < 0.001), but not with the other components of MS. The
levels of 25(OH)D and magnesium were not associated with MS in the multivariate model.
Conclusion: The PTH level, but not the vitamin D level, is an independent predictor of MS in treatment seeking morbidly obese
Caucasian women and men. Randomized controlled clinical trials, including different therapeutic strategies to lower PTH, e.g.
calcium/vitamin D supplementation and weight reduction, are necessary to explore any cause-and-effect relationship.||en