Endocrine disorders - The Thyroid Gland: Hyperthyroidism

Hyperthyroidism (HyperT4)

• Increased T3 and T4

• Very common in cats - rare in dogs

• Feline - thyroid adenoma 98-99% cases - benign

• Canine - malignant thyroid carcinoma

Clinical signs of HyperT4

• Weight loss

• PU/PD/PP

• Tachycardia

• Hyperactivity

• Unkempt appearance

• Palpable goitre

• +/- cardiac arrhythmias, vomiting/diarrhoea, respiratory changes

Diagnosis of HyperT4

• Clinical signs

• Biochemistry - elevated liver enzymes

• Total T4 levels

Dietary management of HyperT4

• Low iodine diet → reduction in thyroid hormone production

• Must not eat anything else - ever!

• No medication, surgery etc ..

• Difficult to achieve

Medical management of HyperT4 - Thiamazole/methimazole

• Tablet (felimazole)

• Liquid (thyronom/thiamcare)

• Topical (transdermal gel - cascade)

Medical management of HyperT4 - Carbimazole - metabolised into thiamazole

Tablet (vidalta)

Medical management of HyperT4 - Human teratogen

• Pregnant or possibly pregnant women wear gloves - could cause birth defects

• Regular monitoring of T4 levels

Thiamazole

• Carbimazole is metabolised into thiamazole

• Thiamazole = methimazole

• Inhibits multiple processes in the production of thyroid hormone

• Does not affect existing thyroid hormone

Thiamazole - pharmacology

• Oral administration

• Formulation impacts half life and dosing interval recommendation

• Administration with food? - different products differ - often advised not to administer with food as it can impact bioavailability

Surgical treatment of HyperT4

• Thyroidectomy

• Can be curative

• Risk of post-op complications - damage to parathyroid gland, recurrence of hyperthyroidism

Radioactive Iodine

• Inject radioactive iodine subcutaneously

• Taken up by the thyroid tumour tissue - including elsewhere

• Requires hospital stay (radioactive) - duration different on hospital, family situation

• Approx. 92-99% success rate

Nursing care for HyperT4

• Surgical considerations - Cardiac abnormalities / low weight / concurrent disease common

• Geriatric patient care - In some cases, concurrent disease will make treatment inadvisable

• Hyperactive behaviour

• Grooming (care!)

• Hygiene (diarrhoea/PUPD etc)

Owner support for HyperT4

• Repeat blood tests may be needed

• Nutritional advice

• Advice on administration on medication

• Regular weight checks

• Advice on safe handling on drugs