The determination of thyroid volume by ultrasound and its relationship to body weight, age, and sex in normal subjects.

Using a precise and accurate ultrasonic scanning technique we have measured the volume of the thyroid gland in vivo in 271 healthy subjects (13-91 yr old). In these subjects the mean (+/- SD) thyroid volume was 18.6 +/- 4.5 ml. A significant difference between males (19.6 +/- 4.7 ml; n = 139) and females (17.5 +/- 4.2 ml; n = 132) was found (P less than 0.001). The thyroid volume was significantly correlated with both body weight and age, described by: Y = 1.97 + 0.21 . x1 + 0.06 . x2, where Y is the thyroid volume (milliters), x1 is the body weight (kilograms), and x2 is the age (years). The influence of body weight on the thyroid volume was about 3 times that of age. The difference in thyroid gland volume between males and females was explained solely by a difference in body weight.