This disease is found commonly in dogs over 7 years of age and is rare in cats. It is the opposite of the HyperT covered previously, as in these animals have a lazy thryoid and low levels of circulating thyroxine. This means their metabolic rate slows down.
Clinical signs can be any of the following: A dry, burnt, faded hair coat, possibly combined with greasy, scurfy skin. Animals may feel the cold more and seek sheltered areas, or spend more time by the fire or heater. You might find they are slow to grow hair back after clipping, or rub areas such as the tail, under the collar etc never grow back and the skin there becomes dark and shiny. Animals often put on weight, and are less active which is commonly passed off as just old age, but in fact is because they feel slow and lethargic.
HypoT is diagnosed via blood tests, and treated with tablet supplementation. Dogs often regain their normal colour and coat quality and become more active and more like 'their old selves'