Share 'Hypothyroidism'

Hello, My older dog Tara (just turned five) has had blood taken tonight to test for hypothyroidism. Does anyone else's dog have this condition? I know treatment would be thyroxine tablets for the rest of her life, but what additional care would she need? Do they have a reduced life expectancy? I'm really hoping the test is negative as she isn't exhibiting all of the symptoms. She has been off...