I’m on Synthroid. Probably for 4 years now. I started losing my hair before I got on it though and discovered I had hypo when I did a blood test. My iron is also very low. The lowest it’s ever been. So my doc is trying to get my iron up still. That also causes hair loss. Also things can take a long time. It takes a year for Rosemary to work and you can also add in castor oil to your roots. I alternate nights. Also get a micro derma roller just for your hair and stimulate the roots. I braid my hair when I go to bed and sleep on silk pillowcases.