What Is The Cause And Treatment For Hypothyroidism?

i am 86 yraes old male with hypothyriodism with 50 micro synthriod for a long time with out symptoms recently tsh wea high so i was put on 75 micro sat and sinday and 50 micro on monday to fridat after 8 weeks on these regime my tsh fell below 1 i.e. o.9 getting mild symtoms of hyperthroidism during day sometime ang goes awat only 3 hours sleep loss of appetite what to do please advice