Prevalence of vitamin D deficiency and its relationship with parathyroid hormone

Objectives: We evaluated the prevalence of 25-hydroxyvitamin D (25-(OH)D) deficiency in our setting, according to the season of the year, sex and age of the subjects. Likewise, we analyzed its relationship with parathyroid hormone (PTH) levels.Methods: The study population consisted of patients with requests for 25-(OH)D analysis between January 1 and December 31, 2018, registered in the laboratory computer system database. Samples from pediatric patients (< 18 years) were excluded, as well as those subjects with factors that could affect 25-(OH)D and/or PTH levels (e.g. renal insufficiency, liver disease, PTH disorders). Results: In the 33,601 patients (24,028 women and 9,573 men), the prevalence of 25-(OH)D deficiency was 48%. A higher prevalence was observed among men compared to women (53% vs. 46%). By age group, prevalence was highest in quartile 1 (Q1, 74-87 years) and lowest in quartile 2 (Q2, 60-73 years). By season of the year, this deficit was higher in spring (non-significant differences with respect to winter) and lower in summer. The relationship between 25-(OH)D and PTH was evaluated in 9,368 individuals. Linear regression analysis showed a weak association (coefficient - 0.303). Multiple logistic regression analysis revealed a significant relationship between 25-(OH)D deficiency and elevated PTH levels (Odds ratio (OR), 1.63). Other risk factors associated with higher PTH levels were sex (OR, 1.27), season (winter, OR 1.63, spring OR 1.16) and age (quartile 1, OR, 3). Conclusions: The prevalence of 25-(OH)D deficiency varied by gender, age and season. In addition, elevated PTH is mainly related to low 25-(OH)D levels, female gender, season and age.