Background: 25 (OH) vitamin D3 (25(OH)D) and parathyroid hormone (PTH) are important regulators of calcium homeostasis. The aim of this study was to retrospectively determine the cut-off for sufficient 25(OH)D in a four-season region and the influence of age, seasons, and gender on serum 25(OH)D and PTH levels.
Methods: Laboratory results of 9890 female and 2723 male individuals aged 38.8±22.1 years who had simultaneous measurements of 25(OH)D and PTH were retrospectively analyzed by statistical softwares. Serum 25(OH)D and PTH levels were measured by a mass spectrometry method and by an electrochemiluminescence immunoassay, respectively.
Results: Mean serum 25(OH)D levels showed a sinusoidal fluctuation throughout the year and were significantly (p<0.01) higher in summer and autumn. On the other hand, PTH levels were significantly higher (p<0.01) in women and showed an opposite response to seasonal effects relative to 25(OH)D. Lowest levels of 25(OH)D were detected in people aged between 20 and 40 years whereas PTH hormone levels were gradually increasing in response to aging. The significant exponential inverse relationship that was found between PTH and 25(OH)D (PTH=exp(4.12-0.064*sqrt(25(OH)D)) (r=-0.325, R- squared=0.105, p<0.001)) suggested that the cut-off for sufficient 25(OH)D should be 75 nmol/L.
Conclusions: Our retrospective study based on large data set supports the suitability of the currently accepted clinical cut-off of 75 nmol/L for sufficient 25(OH)D. However, the issue of assessing Vitamin D deficiency remains difficult due to seasonal variations in serum 25(OH)D. Therefore, PTH measurements should complement 25(OH)D results for diagnosing Vitamin D deficiency. It is imperative that seasonally different criteria should be considered in future.
Uvod: 25 (OH) vitamin D3 (25(OH)D) i paratireoidni hormon (PTH) imaju važnu ulogu u regulisanju homeostaze kalcijuma. Cilj ove studije bio je da se retrospektivno odrede cut-off vrednosti za dovoljan nivo 25(OH)D u regionu sa četiri godišnja doba, kao i uticaj starosti, godišnjeg doba i pola na nivoe 25(OH)D i PTH u serumu.
Metode: Laboratorijski rezultati 9890 žena i 2723 muška rca starosti 38,8±22,1 godina kod kojih su istovremeno mereni 25(OH)D i PTH retrospektivno su analizirani statističkim softverom. Nivoi 25(OH)D i PTH u serumu mereni su metodom masene spektrometrije, odnosno elektrohemiluminiscencije.
Rezultati: Srednji nivoi 25(OH)D pokazali su sinusoidnu fluktuaciju tokom cele godine i bili su značajno viši (p<0,01) u leto i jesen. S druge strane, nivoi PTH bili su značajno viši (p<0,01) kod žena i pokazali su suprotan odgovor na sezonske efekte u odnosu na 25(OH)D. Najniži nivoi 25(OH)D otkriveni su kod ljudi starosti između 20 i 40 godina, dok su hormonski nivoi PTH sa starenjem bili u postepenom porastu. Značajan eksponencijalni obrnut odnos koji je utvrđen između PTH i 25(OH)D (PTH=exp(4,12–0,064* koren2 (25(OH)D)) (r=–0,325, R-na kvadrat=0,105, p<0,001)) ukazao je na to da cut-off vrednost za dovoljan nivo 25(OH)D treba da bude 75 nmol/L.
Zaključak: Naša retrospektivna studija zasnovana na velikim skupinama podataka potvrđuje da je trenutno prihvaćena klinička cut-off vrednost od 75 nmol/L prigodna za dovoljan nivo 25(OH)D. Međutim, utvrđivanje nedostatka vitamina D ostaje teško izvodljivo usled varijacija u serumskom nivou 25(OH)D zbog godišnjih doba. Stoga, merenje PTH trebalo bi da posluži kao komplement rezultatima 25(OH)D prilikom dijagnostikovanja nedostatka vitamina D. Najvažnije je da se u budućnosti razmotre različiti kriterijumi prilagođeni različitim godišnjim dobima.
Keywords: 25(OH)D; parathyroid hormone; vitamin D; vitamin D deficiency.