Increased loss of the Y chromosome in peripheral blood cells in male patients with autoimmune thyroiditis

► Autoimmune thyroiditis (AIT) is characterized by a marked female preponderance. ► The reason for female preponderance in AIT is still unknown. ► We demonstrated that AIT women have a high frequency of blood X monosomic cells. ► We herein demonstrated that male with AIT progressively loss their Y chromosome. ► We surmise an instability of sex chromosome in AIT, with role in disease development.