THYROID GLAND
The thyroid gland is located in the neck, attached to the upper portion of the windpipe, it has two lobes on either side. By producing thyroid hormones, it controls the rate of function for every cell and gland in the body, including growth, repair and metabolism. It’s fair to say that your dog’s health is not optimal when its thyroid gland is not functioning properly.

HYPOTHYROIDISM
Hypothyroidism in dogs is a common disorder resulting from too little production of thyroid hormones by the thyroid gland. It is estimated that 2 - 6 dogs per 1.000 have it.
95 out of 100 adult dogs with hypothyroidism get this is as a result from destruction of their thyroid gland tissue. This is called primary hypothyroidism. An immune mediated disease is the cause in about half of these dogs, which is actually quite similar to man. In the rest of the cases the cause remains unknown.

WHICH DOGS
Most commonly the diagnosis of primary hypothyroidism is set, but not limited, in young adult - and middle aged dogs. Changes in the thyroid gland often begin earlier though, sometimes even as young as 2-3 years of age. It occurs more often in large breeds than in small breeds, whereas it affects males and females about equally.

SYMPTOMS
A deficiency in circulating thyroid hormone decreases the rate of function of almost all organ systems. As a result, signs are variable with many other disorders giving the same symptoms. The clinical symptoms usually start off subtle and progress slowly. As a result, signs may be present for months before you recognise them as a problem and as a consequence you may seek for veterinary assistance late on in the disease.

Behaviour 
Your dog seems tired, sleeps a lot and is reluctant to exercise. Most times the owner incorrectly attributes this to the increasing age of the dog!
Amongst other behavioural changes that have been recognized is (fear induced) aggression. Further scientific research is currently being performed.

Bodyweight
An increase in weight over time without changes in feeding habits can been found in approximately half of the affected dogs.

Skin and coat
In many cases the hair – and or skin condition is poor; e.g. dull or brittle hair coat, hair loss and – retarded re-growth, hair that can be easily extracted from the skin, excessive pigmentation of the skin, very dry or sometimes very oily skin, inflammation which can result in skin infections. Thickening of the skin may present in a so-called ‘sad-face appearance”. 

Doerak - showing signs of sad-face, hair-loss
and hyper pigmentation (black spots) of the skin

DIAGNOSIS 
Because the clinical symptoms are varied and not very specific, they can only raise the suspicion of you and your vet. To be sure of a diagnosis, your vet first has to rule out other diseases. Additionally he needs to take blood samples in which measurements of hormones can be determined. Certain medications can negatively influence the outcome of these blood tests. Some medications administered influence the outcome of these test. If this is the case in your pet, the veterinarian will postpone the blood sampling to a later time.