GAD1 and Autoimmunity: Age was inversely correlated with anti-GAD and anti-islet (r = −0.31, p < 0.001 for both) and positively correlated with anti-TPO (r = 0.36, p < 0.001), suggesting that islet-specific autoimmunity predominates at younger ages, while thyroid autoimmunity becomes more prevalent with aging.