Clinical Case 1 - Page 2

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Case 1 - Courtesy of A. Antonczyk

A blood sample was taken from Shakespeare. The results are shown below:

Biochemistry

Total Protein 68 g/L (54.0 - 80.0)

Albumin 33 g/L (25.0 - 42.0)

Globulin 35 g/L (25.0 - 45.0)

A:G ratio 0.9 (0.6 - 1.5)

Sodium 157 mmol/L (125.0 - 160.0)

Potassium 4.7 mmol/L (3.6 - 6.0)

Total Calcium 2.38 mmol/L (2.0 - 3.0)

Urea 10.9 mmol/L (4.0 - 12.0)

Creatinine 100 umol/L (80 - 180)

ALP 162 U/L (0.1 - 60.0) HIGH

ALT 521 U/L (5.0 - 60.0) HIGH

Total bilirubin 5.8 umol/L (0.1 - 10.0)

Glucose 4.7 mmol/L (3.5 - 6.6)

Haematology

RBC 9.22 x10^12/L (5.5 - 10.0)

Hb 13.3 g/dL (9.0 - 17.0)

HCT 45.2 % (27.0 - 50.0)

MCV 49.0 fl (40.0 - 55.0)

MCH 14.5 pg (13.0 - 21.0)

MCHC 29.5 g/dL (29.0 - 36.5)

Plt 797 x10^9/L (170 - 650) HIGH

WBCs 12.10 x10^9/L (4.0 - 15.0)

Neutrophils 7.99 x10^9/L 66% (2.5 - 12.5)

Lymphocytes 2.30 x10^9/L 19% (1.2 - 7.0)

Monocytes 0.12 x10^9/L 1% (0.0 - 0.8)

Eosinophils 1.57 x10^9/L 13% (0.0 - 1.5) HIGH

Basophils 0.12 x10^9/L 1% (0.0 - 0.2)

Endocrinology

Total T4 304.1 nmol/L (15.0-50.0) HIGH

• 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.

• 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.

• 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.

• How would you treat this case?
  • Shakespeare was treated with methimazole. The licenced product is called Felimazole® (Arnolds Veterinary Products). The initial dose is 2.5mg twice daily. By re-taking the total T4 level 3 weeks later the adequacy of the dose can be determined. If the T4 is still high the dose is increased and another blood sample taken 3 weeks later. 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! 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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