Serum PTH is not a good marker for defining a threshold for vitamin D deficiency. Issue 5 (May 2020)

• Record Type: Journal Article
• Authors: Jorde, Rolf; Grimnes, Guri
• Is Part Of: Endocrine connections. Volume 9:Issue 5(2020)
• Page Start: 396
• Page End: 404
• Publication Date: 2020-05
• Subjects: parathyroid hormone -- thresholds -- vitamin D -- randomized controlled trial; Endocrinology -- Periodicals; 616.4005
• DOI: 10.1530/EC-20-0067
• Languages: English
• ISSNs: 2049-3614

Abstract

Abstract : Objective: In addition to its skeletal effects, vitamin D may also be important for health in general. It is uncertain what level of serum 25-hydroxyvitamin D (25(OH)D), marker of vitamin D status, is sufficient for these effects. With decreasing serum 25(OH)D levels there is an increase in serum PTH. The point at which this occurs has been considered as a threshold for vitamin D sufficiency. The thresholds found have varied widely and have mainly been based on observational studies. However, to truly establish a threshold for vitamin D effects, this has to be based on randomized controlled trials (RCTs). Methods: The study included 2803 subjects from a general health survey, the Tromsø study, and pooled individual person data from five vitamin D intervention studies ( n = 1544). Serum parathyroid hormone (PTH) and change in PTH after vitamin D supplementation were related to serum 25(OH)D levels in steps of 25 nmol/L (<24, 25–49, 50–74, 75–99, and >99 nmol/L). Results: In the Tromsø study, in the females there was a gradual decrease in serum PTH with increasing serum 25(OH)D with no apparent plateau, whereas in the males the decrease in PTH in subjects with serum 25(OH)D >74 nmol/l was marginal. In pooled RCTs, there was a significant reduction in serum PTH by vitamin D supplementation regardless of baseline serum 25(OH)D level. Conclusions: The use of the serum PTH–25(OH)D relation from observational studies to determine a threshold for vitamin D sufficiency is highly questionable.