Feline Hyperthyroidism

Question 1

Hyperthyroidism

Clinical Signs

Answer 1

• Weight loss despite polyphagia
• hyperdefecation +/- steatorrhea
• vx/dx
• PU/PD
• Restlessness, nervousness
• Unkempt hair coat

Question 2

Hyperthyroidism

Physical Findings

Answer 2

• Weight loss (even 1 kg in a 19 kg cat)
• Tachycardia +/- murmur
• Tachypnea
• Palpable Goiters
• +/- hypertension
• +/- Retinal hemorrhage (Start on 11/23)

Question 3

Hyperthyroid DX test

Answer 3

• total T4
  
  • One aside: Cats with chronic renal disease can have an elevated T4

Question 4

Thyrotoxicosis

Apathetic Hyperthyroidism

Answer 4

• extreme hyperthyroidism
• Lacks usual featers of hyperthyroidism, cardiac dz dominates
• cardiac pathologies
  
  • myocardial thickening

Question 5

Apathetic hyperthyroidism signs

Answer 5

• Tachycardia
• Dyspnea
• Abnormal lung sounds
• +/- palpably enlarged thyroid glands
• Rarely seen because of earlier dx

Question 6

Non surgical Tx of hyperthyroidism

Answer 6

• Beta blockers to slow down the heart
  
  • Propranolo
  • atenolol
• If hypertensive
  
  • Amlodipine
• Methimazole/tapazole: anti thyroid drug
• I¹³¹
• Hills diet y/d: devoid of iodine

Question 7

Tapazole/Methimazole action

Answer 7

• Prevents organification of iodide to iodine =>
  
  • prevents syntheses of thyroid hormone

Question 8

Methimazole/Tapazole Toxic Effects

Answer 8

• Anorexia
• Vomiting
• Lethargy
• Facial pruritus => stop the drug
• Bleeding diathesis
• Icterus (hepatotoxicity)

Question 9

Methimazole: Hematologic side effects

Answer 9

• Eosinophilia
• Lymphocytosis
• Leukopenia
• agranulocytosis => stop drug
• Thrombocytopenia
• Positive ANA

Question 10

Surgery - Pre-OP

Answer 10

• Restore euthyroidism pre-op
• Assess KIDNEY function pre-op
• Propranolol or atenolol for tachycardia
• Anesthesia
  
  • avoid atropine
  • acepromazine and ketamine ok

Question 11

Post op

Answer 11

• Monitor for hypocalcemia with bilateral removal
• Treat with Ca gluconate if indicated
• Thyroxine if indicated

Question 12

Renal function after hyperthyroid treatment

Answer 12

• Chronic Kidney disease can benefit from the inc blood flow to kidneys during hyperthyroid states.
  
  • treating the hyperthyroidism can toast the kidneys

Question 13

Hyperthyroidism

Take home message

Answer 13

• Usually older cats
• common signs: weight loss, polyphagia
• Assess cardiac status
• treat with methimazole, and beta blockers
• Do tapazole test before I 131
• Watch out for renal disease
• monitor for hypocalcemia after bilateral thyroidectomy