Hi, Irregular periods can occur due to many causes. Along with thyroid hormonal abnormalities, the other usual causes that lead to irregular periods are reproductive hormonal imbalance as in polycystic ovarian disease, low hemoglobin levels, abnormal blood sugar levels, serum prolactin level changes, etc. So as you have a normal thyroid profile at present you can undergo investigations related to the above factors to find out the possible causes of the problem. Investigations like hemoglobin levels, blood sugar levels, serum prolactin levels and ultrasound can help in finding the possible cause of the problem and treatment can be planned accordingly. Primolut containing progesterone helps in getting the withdrawal bleeding and by cyclical use it can help in achieving regular menstrual cycles in case of reproductive hormonal imbalance. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Sree Gouri S. R., OBGYN