Brief report: Does PTH increase with age, independent of 25-hydroxyvitamin D, phosphate, renal function, and ionized calcium?
BACKGROUND
Circulating PTH concentrations increase with age. It is uncertain whether an age-related PTH increase occurs independent of changes in circulating 25-hydroxyvitamin D, phosphate, renal function, and ionized calcium.


OBJECTIVE
The purpose of this article was to analyze the relationship between PTH and age, controlling for 25-hydroxyvitamin D, phosphate, renal function, and ionized calcium.


METHODS
This was a retrospective, cross-sectional study analyzing the relationship between PTH and age in 2 independent datasets (laboratory 1, n = 17 275 and laboratory 2, n = 4878). We further analyzed subgroups after excluding participants with estimated glomerular filtration rate of <60 mL/min/1.73 m(2) or 25-hydroxyvitamin D of <50 nmol/L (for subgroups, n = 12 051 for laboratory 1 and 3473 for laboratory 2).


RESULTS
After adjustment for sex, ionized calcium, 25-hydroxyvitamin D, phosphate, and estimated glomerular filtration rate, each 10-year increase in age was associated with a 5.0% increase in PTH (95% confidence interval [CI], 4.4%-5.6%; P < .001) in laboratory 1 and a 4.2% increase in laboratory 2 (95% CI, 3.0%-5.4%; P < .001). In the subgroups, each 10-year increase in age was associated with a 6.1% increase in PTH (95% CI, 5.5%-6.8%; P < .001) in laboratory 1 and a 4.9% increase (95% CI 3.5%-6.2%; P < .001) in laboratory 2.


CONCLUSIONS
PTH concentrations increase with age, independent of 25-hydroxyvitamin D, ionized calcium, phosphate, and renal function. Further research is required to explore the underlying mechanisms and clinical relevance and to determine whether the use of age-related PTH reference ranges improves diagnostic accuracy, particularly in elderly individuals.
Department of Clinical Biochemistry (S.J.C., R.W., N.C.H.), PathWest Laboratory Medicine, Queen Elizabeth II Medical Centre, Nedlands, Western Australia 6009, Australia; Department of Endocrinology and Diabetes (S.J.C., J.P.W., S.J.B.), Sir Charles Gairdner Hospital, Nedlands, Western Australia 6009, Australia; and School of Medicine and Pharmacology (J.P.W.) and School of Pathology and Laboratory Medicine (N.C.H.), The University of Western Australia, Crawley, Western Australia 6009, Australia.
Simon J
SJ
Carrivick
John P
JP
Walsh
Suzanne J
SJ
Brown
Robert
R
Wardrop
Narelle C
NC
Hadlow
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000097:blood*; D002118:Calcium / Q000097:blood*; D005260:Female; D006801:Humans; D007668:Kidney / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D010281:Parathyroid Hormone / Q000097:blood*; D010710:Phosphates / Q000097:blood*; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood
D010281:Parathyroid Hormone; D010710:Phosphates; D014807:Vitamin D; C104450:25-hydroxyvitamin D; D002118:Calcium