ACOX1 and hypothyroidism: On day 15 of hypothyroidism only single ACOX1-positive peroxisomes localized closely adjacent to the ER were present, while on other points of hypothyroidism, on days 7 and 21, we found both single ACOX1- and double ACOX1/ACOX3-positive peroxisomes (figures 3 and 5a).