Canine hypothyroidism is the most common endocrine disorder in dogs. It is treatable and manageable, but underdiagnosis means many dogs live with avoidable chronic suffering.
Hypothyroid dogs experience chronic fatigue, weight gain despite normal eating, and a general reduction in vitality and engagement with life. Cold intolerance, skin thickening, and hair loss contribute to discomfort. In more severe cases, peripheral neuropathy causes muscle weakness, ataxia, and — rarely — vestibular disease or facial nerve paralysis. These welfare impacts accumulate gradually and are frequently misattributed to normal ageing, leading to prolonged untreated suffering. The good news is that treatment with oral L-thyroxine is simple, inexpensive, and highly effective. Most dogs show dramatic improvement within 4-8 weeks: returning energy, improved coat condition, and weight normalisation. Twice-daily dosing and periodic monitoring of thyroid hormone levels guides dose adjustment over the dog's lifetime.