[Normal values for adult thyroid volume on ultrasound - where do they come from and how should they be evaluated?]

The upper limit for the thyroid volume is 18 ml for women and 25 ml for men. These reference values are used and taught in many clinics and practices across several disciplines. The thyroid volume is a relevant factor for the treatment course. But where do the standard values for thyroid volumes come from, what kind of studies have been carried out to establish them? Should these upper limits be used as an universal standard in clinical routine, and which factors can influence the physiological organ size? The following article is dedicated to a critical review of the commonly used reference values for the thyroid volume of adults.