Reference range of serum calcitonin levels in humans: influence of calcitonin assays, sex, age, and cigarette smoking

Abstract

ObjectiveThe objective of this study was to re-evaluate the adult CT reference values determined by five different immunoassays and by introducing criteria for selecting control subjects.DesignA prospective multicenter study.PatientsThree hundred and seventy-five clinically euthyroid subjects.MethodsWe used five different CT immunoassays. Sera were assayed for the concentration of TSH, gastrin, procalcitonin, urea, calcium, and anti-thyroperoxidase antibodies.ResultsScreening for the various potential causes of hypercalcitoninemia led to the exclusion of 23% of the sera. Our reference value analysis dealt with 287 subjects (142 men and 145 women). The proportion of samples in which no CT was detected varied from 56% (for assay D) to 88% (for assay C). We observed significant correlations (whose magnitude depended on the assay used) between CT levels and age or body mass index (BMI) (primarily in men). The distribution of CT levels showed that 4.7, 9.8, 2.5, 6.5, and 8.0% of the values were over 10 pg/ml respectively. These values corresponded essentially to samples from 11 male subjects (median age: 55 years), most of whom were smokers. The highest CT values were around twice as high in men than women, and were higher in smokers than non-smokers.ConclusionIn clinical practice (and after having excluded the usual causes of raised CT levels), the interpretation of CT assay results must take into account i) the method used; ii) the patient's gender, age, and weight; and iii) the potential influence of cigarette smoking.