Goiter index: an easily available ultrasonographic index for thyroid volume in autoimmune thyroid diseases.

This study aimed to confirm the applicability of the product of depth and width of the right thyroid lobe measured by ultrasonography, as an index of estimated thyroid volume in patients with Hashimoto thyroiditis. This study included 118 patients with Hashimoto thyroiditis and 163 patients with Graves' disease. The product of depth and width of the right thyroid lobe ranged from 1.7 to 10.2 (median, 4.4) cm² for Hashimoto thyroiditis and 2.6 to 10.8 (median, 5.8) cm² for Graves' disease. The estimated volume obtained by ellipsoidal approximation correlated well with the product of depth and width of the right thyroid lobe in Hashimoto thyroiditis (ρ = 0.820, p < 0.0001) and Graves' disease (ρ = 0.928, p < 0.0001), respectively. However, the correlations were not identical. The comparison of 72 patients with Hashimoto thyroiditis and 72 patients with Graves' disease who were matched for the product of depth and width revealed no significant difference in the estimated thyroid volume. These results show that the product of depth and width of the right thyroid lobe can be applied to indicate thyroid volume instead of the estimated volume obtained from ellipsoidal approximation in both Hashimoto thyroiditis and Graves' disease within the range of volumes investigated in this study.