Feline hyperthyroidism SA

Presenting signs

·    Goitre

·    Increased appetite + weight loss/muscle wasting

·    Hyperactivity

·    Reduced tolerance to stress

·    V+, D+

·    PUPD

·    Tachycardia, cardiac murmur, hypertension

Diagnosis

·    Clinical signs suggestive

·    Total T4

o  Specific – if positive then has hyperT4

o  Low sensitivity – if negative then cant rule out

·    Free T4

o  More sensitive as measures unbound T4

o  But higher chance of false positives

Treatment

·    Radioactive iodine

o  Curative, single SC injection

o  But requires 2w hospitalisation and isolation as will be radioactive

·    Surgery

o  Curative, simple surgery

o  But relies on good anatomical knowledge, risk of removing PT gland

·    Anti-thyroid medication

o  Variety of forms, easy

o  Not curative, just reducing thyroid hormone production, cat on meds for life

·    Dietary management

o  Specific low iodine diet – helps to reduce thyroid hormone production

o  But also low protein – need to monitor BCS

Long term management

·    Regular re-examination, weight check, nutritional assessment, measure TT4

·    If had surgery – monitor for PT-related problems, unmasking kidney disease

·    If had radioactive iodine – monitor for unmasking kidney disease, iatrogenic hypoT4

·    On anti-thyroid medication – any side effects? Check H+B, BP

o  Adverse effects: anorexia, V+, lethargy, face/neck excoriation (or more severe: hepatopathy, leukaemia, anaemia)