Thyroid volume was found to be a determinant of serum calcitonin levels in animal models and in thyroid-healthy subjects, as recently reported. This study aims to evaluate if this finding is confirmed in patients undergoing ultrasonography-guided fine-needle aspiration cytology of suspicious thyroid nodules. A dataset of 561 patients including basal serum FT4, FT3, TSH, calcitonin, thyroid volume, anti-thyroperoxidase antibodies (TPOAb), and cytology report, was retrospectively analysed. The median thyroid volume was 20.5 ml (14.5-26.8) in males and 12.0 ml (9.3-17.0) in females (p