Thyroid volume, lobe asymmetry and AP diameter classification - A preliminary study

ObjectiveTo assess the thyroid lobe volumes and the total thyroid volumes across the arbitrary range for AP diameter of thyroid lobes, the age and sex related variation and compare local normal sizes with those in the reference. Because assessment of thyroid gland size by visual comparison with anatomical relations or by an arbitrary category for antero-posterior (AP) diameter precludes use of management guidelines based on thyroid gland volume. Moreover, the international references for AP diameter seem larger for Bangladeshi patients and therefore deemed as inapplicable. MethodsPatients who underwent thyroid ultrasound with thyroid volume measurements from October 2023 to October 2024 were included. The patients were classified into two groups. Group 1 consisted of children aged below 15 years while group 2 consisted of adolescents aged 15 years or more and all adults. Statistical analyses were applied to assess distribution of gland size between sexes and age groups, correlation between gland size and age, and distribution of thyroid lobe volume and total gland volume, across the arbitrary categories of AP diameter. ResultsTotal 110 patients (90 females) with mean ({+/-} SD) age of 28.1 {+/-} 13.2 were included. There was no significant difference of gland size between males and females. The AP diameter and right thyroid lobe was significantly larger than the left in group 2 consisting of adolescents and adults (p < 0.05). There was a positive correlation of thyroid size and age in group 1 consisting of pre-adolescents who had normal sized glands (R = 0.91, p < 0.01). Observation of thyroid volumes across the arbitrary AP diameter category showed AP diameter categories of right lobe tended to better classify the normal glands whereas the AP diameter categories of left lobe tended to perform better for classification of the enlarged glands. ConclusionsThis study apart from describing the interaction of age and sex with thyroid size, highlights the importance of considering the natural asymmetry between the thyroid lobes for accurate thyroid volume classification. This study points toward the void for a reference local standard of thyroid volume that can classify not only the different categories of enlargement but also the small volume glands.