Adverse reaction reports describe suspected side effects. A report does not mean the drug caused the event — co-medications, underlying disease and coincidence all contribute.
Is Levothyroxine Sodium Tablets approved in United States?
Yes. FDA has authorised it.
Who is the marketing authorisation holder for Levothyroxine Sodium Tablets in United States?
Second Affiliated Hospital, School of Medicine, Zhejiang University is the originator. The local marketing authorisation holder may differ — check the official source linked above.