Vitamin D, Parathyroid Hormone Levels, and the Prevalence of Metabolic Syndrome in Community-Dwelling Older Adults

Abstract

OBJECTIVE -Accumulating research suggests low-circulating vitamin D concentrations, i.e., 25-hydroxyvitamin-D [25(OH)D], may be associated with an increased prevalence of metabolic syndrome; however, previous studies have not accounted for parathyroid hormone (PTH) levels. We examined the association of 25(OH)D and PTH with the prevalence of metabolic syndrome in a community-based cohort of older adults. RESULTS -In men, there was a significant trend (P ϭ 0.03) of increasing adjusted odds for metabolic syndrome with increasing PTH concentrations, primarily due to an odds ratio of 2.02 (95% CI 0.96 -4.24) in men in the top quintile (Ն63 ng/l) of PTH concentration. This association remained unchanged after taking into account 25(OH)D levels and excluding men with diabetes or impaired renal function; it was attenuated after adjustment for the homeostasis model assessment of insulin resistance. Neither PTH in women nor 25(OH)D levels in either sex was related to the metabolic syndrome. RESEARCH DESIGN AND METHODSCONCLUSIONS -These findings suggest an increased risk of metabolic syndrome with elevated PTH levels in older men and no effect of 25(OH)D concentrations in either sex. The reason for the sex difference in the PTH-metabolic syndrome association is unknown. Prospective studies are necessary to better determine the roles of 25(OH)D and PTH in the etiology of metabolic syndrome. Diabetes Care 30:1549-1555, 2007D ecreased vitamin D and elevated parathyroid hormone (PTH) levels may play a role in the etiology of metabolic syndrome, either through an association with individual components of metabolic syndrome or via insulin resistance (1,2). Vitamin D levels have been shown to be inversely related both with fasting glucose concentrations (3-5) and adiposity (6 -10) and have been suspected to be involved in the regulation of blood pressure, based on blood pressure reduction with vitamin D 3 supplementation in patients with essential hypertension (11,12). Other evidence suggests a role for vitamin D in maintaining normal insulin synthesis and secretion (13,14). Vitamin D and PTH are both responsible for maintaining extracellular calcium homeostasis (19). Vitamin D increases the efficiency of intestinal calcium absorption, and PTH is secreted in response to low-circulating calcium concentrations. Elevated PTH secondary to low vitamin D increases calcium resorption from the skeleton at the expense of an increased risk of fracture (20). Secondary hyperparathyroidism may also increase the risk of developing components of metabolic syndrome, including hypertension (21-26), obesity (6,9,10,27-29), and diabetes (30 -32). However, we are unaware of previous research investigating whether PTH levels are also associated with the metabolic syndrome.Previous studies linking low 25(OH)D with an increased prevalence of metabolic syndrome (1,18) were limited by their inability to simultaneously account for PTH, since both vitamin D and PTH operate within a tightly controlled feedback system to maintain extracellular calcium conce...

Vitamin D status and metabolic syndrome in Asian Indians

“…16 Interestingly, Asian Indians have been included in the category of 'metabolically obese normal weight' group, as they tend to have more disproportionately higher total body fat at any given BMI compared with those of the other ethnicities 7,17 that might also lead to a false characterization of individuals as vitamin D deficient, based on their serum estimates. We found a lack of association between serum 25-OH-D concentrations and MS. Our observations are in line with those of Reis et al, 18 who demonstrated lack of association between serum vitamin D levels and MS in adult Caucasian population from the southern California community of Rancho Bernardo. In the Longitudinal Aging Study conducted in old subjects in Amsterdam, Snijder et al 19 failed to find any association between diabetes and 25-OH vitamin D. Similarly, Scragg et al 6 observed no association between vitamin D status and type 2 diabetes in non-Hispanic blacks despite their poor vitamin D status and independent associations between 25-OH-D and risk of diabetes in other ethnicities (non-Hispanic whites and Mexican-Americans).…”

Serum 25-hydroxyvitamin D and parathyroid hormone levels in relation to blood pressure in a cross-sectional study in older Chinese men

“…These findings are supported by results of some observational studies, 31,32 but not the others. 16,21,33 In the Longitudinal Ageing Study Amsterdam, serum PTH rather than serum 25OHD was associated with SBP or DBP, or prevalence of hypertension in 1205 men and women aged 65 years and older after adjustment of potential confounders.…”

Study of vitamin D levels and its correlation with insulin resistance

“…[17] Other studies did not find such association. [18,19] This difference from our study can be explained on the basis of very large sample size and difference in ethnicity of the sample. One more study by Sheena et al had demonstrated independent associations of vitamin D with insulin sensitivity and beta-cell function in [21] as did Inzucchi et al in diabetic patients.…”