Hypothyrodism is a common endocrinopathy in dogs. The first alternative in diagnosis is TSH stimulation test, which is expensive and unavailable. In this study, TRH stimulation test was applied to 10 dogs with clinical hypothyroidism symptoms. It was observed that 3 dogs with low basal TT4 values showed normal stimulation, 3 dogs had both normal basal 774 values and stimulation, where 4 dogs with normal basal TT4 values did not reveal normal stimulation with TRH. In conclusion, since TRH stimulation test reliably eliminates hypothyroidism, but insufficient stimulation may be evaluated as suspicious hypotbyroidism, because of the expensiveness and inavailability of TSH stimulation test, Protirelin may be used as the first step in diagnosis of hypothyroidism.