TPO and Hashimoto thyroiditis: Heterogeneity was very high (I2 > 75%) in the Hashimoto’s thyroiditis group, moderately high (I2 = 50-75%) in the age, TSH, anti-TPO and anti-Tg groups, and low (I2 < 50%) for female sex, TSH ≥ 2 mIU/L and side of hemithyroidectomy groups.