| ObjectiveThe aim of this study was to investigate the levels of vitamin D?25?OH?D?and vitamin D binding protein?DBP?in patients with benign thyroid nodules?BTN?and thyroid cancer?TC?,and to explore the association between the levels of 25?OH?D,DBP and risk of BTN and TC,and to provide a theoretical basis for the prevention and control of thyroid related diseases.MethodsFrom May 2017 to October 2018,the first incident primary patients with BTN and TC were recruited from three general hospitals,namely,the First Affiliated Hospital of China University of Science and Technology?Western District?Anhui Provincial Cancer Hospital,First Affiliated Hospital of Anhui Medical University,and Second Affiliated Hospital of Anhui Medical University.At the same time,the controls were selected at those hospitals and matched to the cases on sex,age??5 years?and date of blood collection??30 days?.All the subjects provided fasting blood and urine samples and completed a questionnaire about basic demographic characteristics,lifestyle habits,medical history,female reproductive and reproductive history,and the use of vitamin D and calcium supplements was completed.The concentration of plasma 25?OH?D was determined by radioimmunoassay,and the concentration of DBP was determined by enzyme-linked immunosorbent assay.The molar ratio of 25?OH?D to DBP concentration?25?OH?D:DBP?,a proxy for free 25?OH?D,was calculated.Season-specific variables of 25?OH?D was created based on the distribution among the controls.Season-standardized 25?OH?D was calculated by using local weighted regression scatter smoothing.Multivariate analysis was performed using conditional and unconditional logistic regression models to evaluate the odds ratio?OR?and 95%confidence interval?CI?between 25?OH?D,DBP,25?OH?D:DBP and risk of BTN and TC,respectively.ResultsA total of 419 pairs of TC patients and controls?TC group and controls group matched by 1:1?,198 BTN patients and 396 controls?BTN group and controls group matched by1:2?were included in this analysis.The median age of TC patients was 48 years old,the median age of BTN patients was 49 years old,and the median age of all control subjects was 50 years old,and there was no statistically significant difference between three groups.Among 419 controls,the median concentration of male and female 25?OH?D was 47.8 nmol/L and 43.7 nmol/L,respectively,and the difference between male and female was statistically significant.There only 148 plasma 25?OH?D levels were sufficient among all controls?accounting for 35.3%?.Univariate analysis showed that body mass index,family history of thyroid disease,urinary iodine level after creatinine correction,DBP and 25?OH?D:DBP were all associated with the risk of BTN and TC.After adjusting for potential interference factors,the conditional logistic regression model showed that BTN risk was not associated with plasma 25?OH?D(Quartile 4 vs Quartile 1:OR=1.24,95%CI=0.65-2.37,P–trend=0.409)and 25?OH?D:DBP(Quartile 4 vs Quartile 1:OR=1.66,95%CI=0.87-3.17,P–trend=0.089),but inversely associated with DBP levels(Quartile 4 vs Quartile 1,OR=0.32,95%CI=0.16-0.65,P–trend=0.002).Compared with the first quartile levels of 25?OH?D,the risk of TC was lower in people at the fourth quartile of 25?OH?D(OR=0.59,95%CI=0.35-0.99,P–trend=0.026).In addition,higher plasma DBP levels were associated with a lower risk of TC(Quartile 4 vs Quartile 1,OR=0.49,95%CI=0.29-0.85,P–trend<0.001).According to the clinically pathological features of TC,the subgroup analysis found that lower levels of DBP were associated with an increased risk of those TC whose characteristics were tumor size<1.0 cm,absent extrathyroidal extension and unifocal tumor.ConclusionPlasma vitamin D deficiency was common in this study population,and the average concentration of female population was lower than that of males.The risk of BTN may be inversely associated with plasma DBP levels.An increased risk of TC may be associated with the lower levels of plasma 25?OH?D and DBP. |
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