English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Dear Editor, We read with interest the recent article by Katrinaki et al. (1). The authors report on cross-sectional values of serum 25-hydroxyvitamin D [25(OH)D] concentration from a large Mediterranean cohort in Crete, Greece. One of the major findings of the study was the sharp decline of parathyroid hormone (PTH) concentrations below the upper reference range of 65 pg/ml, with a non-significant decrease above ~20 ng/ml 25(OH)D. This led the authors to conclude that a cut-off level of 20 ng/ml is optimal to avoid secondary hyperparathyroidism in this specific population. The study provides useful novel, large scale results, from a Mediterranean region where vitamin D deficiency is highly prevalent (2). These findings however, contradict a previous large scale study in the U.S.  which found that PTH decreased monotonically to 25(OH)D concentrations above 70 ng/mL (3). Although of potential interest, a continuous report of the PTH curve with regard to higher 25(OH)D concentrations is not provided in the paper by Katrinaki et al. (1) and the authors report metabolic parameters inversely correlated with 25OHD in Figure 3, with no plateau or saturation (1) . In the same previous large scale study (3), a significant part of the population with normal PTH levels ( 30 ng/mL (4). Further specific concerns regarding the interpretation of study findings, lie in the accuracy of the analyses and in particular the 25(OH)D results determined by chemiluminescence especially the claim that  ‘the majority or protein-bound 25-(OH)D was released’ .The evidence for this statement is absent as is a reference to qualify the comment contradicted in the literature. In conclusion, we believe that available evidence (3-5), does not support that 25(OH) D concentrations of 20 ng/mL could be considered as the normal cut-off value for estimating vitamin D status. Additional studies of vitamin D replacement and treatment showing changes in specific patient-important outcomes (4) at certain levels of 25(OH)D are needed and would provide higher quality evidence that would lead to stronger recommendations.

Defining optimal vitamin D cut-off levels: Τhe role of parathyroid hormone concentrations