Association of Leptin, 25-Hydroxyvitamin D, and Parathyroid Hormone in Women

Abstract

Vitamin D deficiency and adipocytokines have been implicated in the etiology of aging-related diseases such as cancer, osteoporosis, and diseases of the cardiovascular system. The association between elevated parathyroid hormone (PTH) and low 25-hydroxyvitamin D (25-OH-VitD) in plasma is used to define vitamin D deficiency, yet their associated mechanistic pathways are unclear. Utilizing plasma samples from women in a previous intervention study, we measured plasma 25-OH-VitD, leptin, adiponectin, PTH, and lipid levels. We observed strong positive associations for leptin with PTH, γ -tocopherol, and body mass index (BMI) and inverse associations with 25-OH-VitD and adiponectin. Although commonly accepted that vitamin D deficiency causes hyperparathyroidism, we observed this association primarily in individuals with elevated leptin levels, suggesting that leptin may be an important modifier of this effect consistent with 25-OH-VitD-mediated inhibition of leptin. Leptin was highly correlated with the BMI/25-OH-VitD ratio (r = 0.80; P < 0.0001), consistent with a model in which BMI (adiposity) and 25-OH-VitD are the primary determinants of circulating leptin and PTH levels. This model may explain the failure of some studies to observe elevated PTH in vitamin D deficient adolescents and provides important insight into epidemiological studies exploring the associations of these individual biomarkers with chronic disease risk and mortality.

Notes

^a Abbreviations are as follows: PTH, parathyroid hormone; BMI, body mass index.

^b n = 16.

^c n = 13.

^d W/B = within to between variance.

^a Abbreviations are as follows: Data for 29 women in the study were stratified by analyte of plasma leptin and mean values ± SEM for each tertile determined. Different subscripts indicate statistically different means.

^b n = 9.

^c n = 10.

^d df = (2, 26).

^e df = (2,25).