Hypothyroidism is a common hormonal disorder in middle-aged dogs that is highly manageable with appropriate medication and monitoring.
Untreated or under-treated hypothyroidism causes chronic, pervasive welfare impacts. Dogs feel lethargic, gain weight that strains joints and cardiovascular health, and may develop skin infections from the reduced immune function. Some dogs experience peripheral neuropathy and vestibular signs. The good news is that hypothyroidism is among the most manageable endocrine conditions in dogs — once correctly dosed on levothyroxine, most show dramatic improvement within weeks. Regular monitoring (every 6 months) is important because dosing needs can change. Owners often report their dog's personality transforming after treatment begins, reflecting how significantly the condition was affecting wellbeing.