Can animals have thyroid problems?

The thyroid is a small gland that plays a key role in the functioning of the whole body. It regulates metabolism, influencing how an animal’s body manages its energy. In veterinary practice, however, we see a clear split between species when it comes to diseases of this gland.

When the thyroid is diseased, a dog’s metabolism usually slows down abnormally, whereas a cat’s speeds up dangerously. Below we explain how differently these conditions present in the two species.

The thyroid in dogs and cats – key differences in pathophysiology

Pet owners are often unaware that dogs and cats suffer from two completely opposite thyroid disorders:

• Dogs most commonly suffer from hypothyroidism. Their metabolism slows to below the physiological norm. The cause is usually an autoimmune process (lymphocytic thyroiditis) in which the immune system destroys the gland’s tissue.
• Cats (especially older ones) struggle with hyperthyroidism. Their body runs in overdrive, which gradually wears out the internal organs. The disease is most often caused by benign growths (adenomas) that produce an excess of hormones.

Because these conditions run such different courses, their diagnosis and clinical picture call for an individual approach.

Hypothyroidism in dogs – clinical signs and predisposition

Hypothyroidism develops slowly. Owners often mistake the symptoms for the natural ageing of their pet. In reality, they are the result of a hormone deficiency.

Main symptoms in dogs:

• Weight gain unrelated to diet: the dog puts on weight despite eating the same amount of food, or even with a reduced appetite.
• Cold intolerance: the animal seeks out sources of warmth and is reluctant to go outside on cold days.
• Behavioural changes (lethargy): apathy, reluctance to exercise, tiring quickly and muscle weakness.
• A characteristic facial expression: the so-called “tragic expression” (facies tragica), caused by myxoedema, a swelling of the skin of the head and eyelids.
• Skin and coat signs: symmetrical hair loss (often on the flanks), a dry, dull coat, and hair loss on the tail (the so-called “rat tail”).

Predisposed breeds:

Owners of breeds such as the Golden Retriever, Labrador, Dobermann, Boxer and Cocker Spaniel should pay particular attention to thyroid screening.

Hyperthyroidism in cats – a threat to geriatric patients

Hyperthyroidism is one of the most frequently diagnosed endocrine diseases in cats over 8 years of age. It forces the cardiovascular system and the kidneys to work overtime, which, if left untreated, can lead to serious complications.

Main symptoms in cats:

• Polyphagia (excessive hunger) combined with weight loss: the cat has an increased appetite yet still loses weight. Muscle wasting along the spine is often visible.
• Restlessness and hyperactivity: a change in behaviour, anxiety, increased activity (including at night), and sometimes irritability or aggression.
• Seeking out cool places: hyperthyroid cats often lie on cold surfaces (tiles) to bring their body temperature down.
• Digestive signs: vomiting and diarrhoea caused by speeded-up gut motility.
• Coat changes: the coat becomes unkempt, greasy and scruffy.

Diagnosis – why a routine blood count is not enough

A standard preventive blood test (basic haematology and biochemistry) can only hint at a problem; it does not allow a definitive endocrine diagnosis to be made. To confirm the disease, at Zviropolis we run a specialist thyroid profile.

It includes measuring the key parameters:

1. T4 (total thyroxine): the basic screening parameter.
2. fT4 (free thyroxine): a more sensitive parameter, unaffected by other systemic diseases.
3. TSH (thyroid-stimulating hormone): essential for confirming hypothyroidism in dogs.

Preparing for the test:

Reliable results depend on the patient being properly prepared. The animal should be brought in for the blood sample fasted (at least 8-12 hours without food) to avoid lipaemia (fat in the serum), which can distort the hormone readings.

Treatment and prognosis

The aim of treatment is to restore euthyroidism (normal hormone levels) and improve the patient’s quality of life.

In dogs (hypothyroidism):

Treatment consists of lifelong supplementation with synthetic levothyroxine. It is a safe and effective therapy. Once the right dose has been established, the clinical signs resolve and the animal returns to normal condition and activity.

In cats (hyperthyroidism):

Management is more complex and is tailored to the individual patient’s condition. The available options are:

• Medication: drugs that block the synthesis of thyroid hormones (given orally).
• Veterinary diet: foods with a strictly limited iodine content.
• Interventional methods: surgical removal of the affected thyroid lobe (thyroidectomy) or radioactive iodine therapy.

In cats, treatment requires close monitoring of kidney parameters.

Thyroid disorders, though common, lead to serious health consequences if left untreated. If you notice unexplained weight gain and apathy in your dog, or restlessness despite weight loss in your older cat, we recommend a veterinary consultation. At Zviropolis we have the diagnostic facilities to assess your pet’s endocrine function precisely. Early diagnosis is the key to effective treatment. Do get in touch.