Hello, Thanks for writing to Health Care magic, I am Dr , Muhammad Ahmad , I have read your question closely, I understand your concern and will be helping you with your health related problem. If her thyroid levels are in normal range then hair loss my not be caused by levo thyroxine , there might be so many other causes including thyroid problems, like vitamin deficiency , fungal infections, age related fall, lack of care and hair treatment. You ca also visit a dermatologist regarding her hair fall problem if dermatologist recommends then supplementation of vitamin and zinc can be opted. Your plan is right you can check her thyroid levels if they are deranged , they should be corrected , if they are fine then other causes can be considered. I hope this answered your question, If you have more queries I am happy to answer you. Regards. Dr.Muhammad Ahmad