Why i m getting late period ?

i was getting late periods before 3 mnth. it was abt 15 days late. so i did hormon test and my TSH was high. now i m taking 75 mcg euthyroxine tablet.now my TSH level has come to 4.53. but still after taking the medicine from 2 mnth i m getting late periods. this time also its 15 days late. what should be the reason? is it bcos of thyroid pills?