Glomerular filtration rate is a major determinant of the relationship between 25-hydroxyvitamin D and parathyroid hormone.
The reference range for 25-hydroxyvitamin D (25-OHD) remains uncertain, and it is not clear as to whether interpretation of circulating 25-OHD would be aided by simultaneous measurement of serum parathyroid hormone (PTH). We wanted to define the level of serum 25-OHD associated with a raised serum PTH and to examine the determinants of the relationship between serum 25-OHD and serum PTH concentration. We retrospectively examined data for patients who had a 25-OHD measurement and other biochemical variables over a 12-month period in our center. We found that 28% of patients had a serum 25-OHD level below 50 nmol/L and serum PTH level in the normal reference range, whereas 24% had a serum 25-OHD level below 50 nmol/L with a serum PTH value above the normal reference range. At a serum 25-OHD level of 80 nmol/L, 1.5% had an elevated serum PTH and, at 50 nmol/L, 8% had raised serum PTH. Further examination showed that for patients with low serum 25-OHD, low glomerular filtration rate (GFR) was a major determinant of the PTH response. These data confirm an inverse correlation between serum 25-OHD and serum PTH. Minimal numbers of patients (1.5% of the study group) have a raised serum PTH at a serum 25-OHD level of 80 nmol/L. GFR is a major determinant of the PTH response to decreasing serum levels of 25-OHD.
Patel
S
S
Department of Rheumatology, St. Helier University Hospital, Carshalton, Surrey, SM5 1AA, UK. sanjeev.patel@epsom-sthelier.nhs.uk
Hyer
S
S
Barron
J
J
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D005919:Glomerular Filtration Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010281:Parathyroid Hormone / Q000097:blood*; D015995:Prevalence; D012189:Retrospective Studies; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood; D014808:Vitamin D Deficiency / Q000097:blood / Q000453:epidemiology
C470125:PTH protein, human; D010281:Parathyroid Hormone; D014807:Vitamin D; C104450:25-hydroxyvitamin D