Hi Thanks for posting on HCM Out of pregnancy, delayed period could be cause by many medical conditions some of which are: -Thyroid irregularity as it could most likely be in your case -Stress -Excess exercise/weight loss -Polycystic ovarian disease -Hormonal imbalance Its true your thyroid problems might best explain you delayed period but these other cause are still possible and only a keen medical examination and work-ups can rule out other causes. Duphaston is a synthetic progesteron that can hlep regularise your menses or at least give you menses if caused by absence of ovulation.But you took it for three days only.I will suggest you take for say 7 to 10 days and stop.A withdrawal bleeding will tell us your delayed period was due to absence of ovulation.You may however have to take duphaston longer to correct the problem. I will also advise you meet an Endocrinologist to take care of your thyroid disorder as correcting that alone might give you normal menses. Hope my answer will help you Best regards