Association of 25-hydroxyvitamin D and parathyroid hormone with the metabolic syndrome in black South African women

Abstract

The relationship between 25 hydroxyvitamin D (25(OH)D), parathyroid hormone (PTH) and metabolic traits appear to differ among ethnicities and may be influenced by obesity. The aim of the study was to examine the association of serum 25(OH)D or PTH with metabolic syndrome (MetS) while controlling for adiposity in black women. Using a cross-sectional study design, 209 urban black women aged ≥ 43 years from the North West Province, South Africa, were included. Multiple regression models were used to explore the relationship between 25(OH)D or PTH and body composition. To explore the association between 25(OH)D or PTH and MetS, a separate variable was created including at least 3 of the MetS criteria, but excluding elevated waist circumference as a diagnostic criterion in a logistic regression model. The majority of the women (69.9%) were overweight or obese and 65.5% of the women had excessive adiposity using the age-specific cut-off points for body fat percentage. All body composition variables were positively associated with PTH, whereas body mass index and waist circumference, but not body fat percentage, had negative associations with 25(OH)D also after adjusting for confounders. Before and after adjusting for age, body fat, habitual physical activity, tobacco use, season of data collection, and estimated glomerular filtration rate, neither 25(OH)D nor PTH showed significant associations with MetS. Although PTH was positively associated and 25(OH)D was negatively associated with adiposity in black women, there was no association between either 25(OH)D or PTH and MetS in this study population, nor did adiposity influence these relationships.

Keywords: 25(OH)D; PTH; adiposity; adiposité; metabolic syndrome; obesity; obésité; syndrome métabolique.