Tag Archives: methimazol

Cami has difficult breathing: why hyperthyroid cats develop cardiac abnormalities.

16 Feb

Cami is a 17 years-old male cat that has presented due to dyspnea (abnormal breathing).


Cami has been vomiting for some months and his owners have noticed that he is not doing well.

Moreover, today Cami is very (too much) quiet and he does not breath normally.

His owner has seen some episodes that he calls “convulsions” and fortunately, he has sent us videos for us to see what happens to Cami; this is very helpful, provided that Cami does not show these signs when he comes to our practice.

These videos allow us to see that Cami suffers syncopes, that can be very similar to convulsions related to epilepsy.

Cami is difficult to manage and examining him is a real challenge. We have made a thoracic radiograph that has shown a pleural effusion (fluid accumulation in the pleural cavity) of Cami. This can be a reason of his syncopes.

According to cat´s age, symptoms and laboratory tests results, we have suspected Hyperthyroidism and we have asked the lab for a blood thyroid hormone level (Thyroxine, T4).

Results have confirmed Hypothyroidism ( 110; normal reference values: 7.8- 42.7)

Hyperthyroidism is a disease produced by a thyroid tumor which is usually benign: this tumor produces an excessive amount of thyroid hormones.

Most commonly affected cats are older than 8 year, and products against external parasites as well as canned food have been shown to increase the risk of developping this disease. Cans, plastic bottles contain chemical substances that can act as “hormonal disrupters” even in humans; during the last 20 years, puberty has advanced in women by 1.5-2 years depending on the region considered.

Hyperthyroidism clinical signs are due to metabolism acceleration by increased  thyroid hormone blood level; cats show weight loss in spite of increased appetite, vomiting or diarrhea. They can be either  hyperactive or too calm, showing thus behaviour changes. They can be dehydrated and present cardiac abnormalities.

Cami is a hyperthyroid cat that shows severe cardiac abnormalities. Sometimes, thyroid hormone excess induces cardiac hypertrophy: heart muscle enlarges, and enlarged cardiac “walls” reduce cardiac ability to pump blood.

The organs needing a highest blood supply  are brain and kidneys. Thus, inadequate blood supply can cause syncopes.

Inadequate heart pumping can also cause liquid accumulation in several locations; one of them is pleural cavity. Cami suffers from pleural effusion, as we have seen in previously shown radiographs.

We start treating Cami by improving his breathing:  a thoracic fluid drainage is made. We also help by using diuretics (that eliminate fluid through urine) and oxygen therapy.

Pleural effusion sample from Cami.
Once stabilized, hyperthyroidism treatment can be started by administering oral methimazol. The key point to success is cat collaboration by accepting to swallow this drug.
The owner´s role is capital in hyperthyroid cats response to treatment, as they are the persons who can try to convince the cat to accept treatment.
Very often, cardiac hypertrophy reverses with hyperthyroidism treatment. 

Now Cami will need initially a 2 week-apart blood test to check if T4 levels are normalizing.

Checking renal function is important as hyperthyroidism can mask renal insufficiency by increasing blood flow to the kidneys; when hyperthyroidism disappears, kidney blood flow normalizes and renal insufficiency can show up.

I´ll let you know how Cami is doing in the next future,


Iris Pérez and David Prandi

Clinica Veterinaria Betulia

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