Inadequate levels of TSH cause the thyroid gland to atrophy. This is one reason why early diagnosis and intervention of thyroid disorders is so necessary. Once the thyroid gland has atrophied, it cannot recover. Secretion of TSH is 'turned off' when plasma concentrations of thyroid hormone are sufficient and is turned back on again when levels fall once more. Clinical Signs Clinical signs of the disease vary greatly because of the myriad of systems the thyroid hormone impacts.
Most owners are alerted to a problem when changes in the dog's coat occur.
This is frequently the first symptom of which they become aware. The classical signs include alopecia or hair loss on both sides of the trunk or specifically on the tail, i.e., the 'rat' tail. Hair regrowth is usually slow and may come in dry, dull or differently colored. The skin may also change color and become greasy, strong smelling and thickened. The dog may gain weight easily, becoming lethargic, mentally dull and exercise intolerant.