Clinical Case 1
"Shakespeare", a 16 year old domestic short hair cat is brought to the practice for examination.
The owner is concerned that Shakespeare has lost weight over the past few weeks. Shakespeare has always been a fussy eater, but recently the owner has noticed that he is asking for food constantly. He has also started to raid the kitchen bin.
The owner is not sure how much Shakespeare drinks, as he usually drinks from the fish pond in the garden.
On clinical examination, the vet finds the following:
- Shakespeare is thin
- There is a moderate amount of tartar on the upper molars and canines
- The heart rate is 244, with a grade 2/6 murmur
- Shakespeare's temperature is 38.4°C
| Question | Answer | Article | |
| Is Shakespeare's temperature normal? | Yes
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| What is the normal heart rate for a cat? Is Shakespeare's heart rate high? | 140-200 beats per minute in the examination room. Most cats in the exam room are stressed to some extent. Their heart rate is probably much lower at home. Very frightened cats may have a heart rate slightly above 200, but Shakespeare is tachycardic.
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| What does 'grade 2/6 heart murmur' mean? | Heart murmurs are graded according to their intensity. A grade 2/6 murmur is one that is readily audible, but is quieter than the heart sounds.
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| What else might you find on clinical exam that will help you with your diagnosis? | Shakespeare's history and clinical exam is typical of a cat with hyperthyroidism. Most hyperthyroid cats will have a palpatable goitre. The location of the thyroid gland is variable. Therefore, make sure to slide your fingers alongside the entire trachea, or you may miss it. Shakespeare did have a palpatable goitre.
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| What would you do now? | A blood sample was taken from Shakespeare. The results are shown below:
Biochemistry
Haematology
Endocrinology
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| What is your diagnosis? | Shakespeare is hyperthyroid. T4 is over 6 times higher than it should be. ALP and ALT are increased which is very common in hyperthryoid cats, with approximately 9 out of 10 animals having raised enzyme levels.
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| What are ALP and ALT short for? Where in the body do these enzymes come from? | ALP is short for alkaline phosphatase. This enzyme is bound to the plasma membrane of hepatocytes and is also present in bone. ALT is short for alanine aminotransferase. This enzyme is found in the cytoplasm of hepatocytes and in muscle.
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| What else might cause an increase in ALP in a cat, in the absence of jaundice? | If an increase in ALP is due to liver damage, this is almost always severe enough to cause jaundice. In a cat that is not jaundiced, an increase in ALP is almost always due to hyperthyroidism. |
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| How would you treat this case? | Shakespeare was treated with methimazole. By re-taking the total T4 level 3 weeks later the adequacy of the dose can be determined. It is important to satisfy yourself that the client is managing to give the tablets since in that case the cause of a second high T4 may be due to failure of the owner to administer the tablets! Carbimazole may also be used in some instances.
There are other treatment options. Surgical removal of the thyroid gland is possible. However, with unilateral excision there is a risk of recurrence (even if the other gland looks normal) and with bilateral excision there is a risk of iatrogenic hypoparathyroidism. Since hyperthyroid cats are high risk anaesthetic patients, they should be treated medically first. Another treatment, the current treatment of choice, is radioactive iodine treatment. Radioactive iodine concentrates in the thyroid gland and destroys it. However, few practices carry out this treatment, so the animal must usually be referred and the cat must remain at the centre for a long time. |
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The question was provided by C. Antonczyk.