Elly Pittaway

Broad Lane Vets, Coventry, United Kingdom

Objectives

Hypothyroidism is well-documented in dogs, but rare in cats (mainly reported when iatrogenic, following radioactive iodine therapy). Here, an unusual case of presumed CFH is described.

Methods

A 6week old male DSH kitten presented with poor appetite and diarrhoea. He was small (0.39kg), with a pot-belly and fleas (treated with fenbendazole and fipronil spray). 2weeks’ later at first vaccination, now weighing 0.61kg, his owner was concerned his faeces were very firm. A few days later he presented with decreased appetite, abdominal swelling and faecal tenesmus. Sodium citrate pr and intravenous fluids were administered but the episodes recurred. Sterculia, lactulose, H2-antagonists, metoclopramide, opiate analgesia and probiotics, along with dietary manipulation, all led to insufficient improvement, and by the time of second vaccination he had barely grown, weighing just 0.625kg. Radiographs were unremarkable. A blood sample was taken.

Results

Haematology and biochemistry were unremarkable, but low total T4/high TSH/low free T4, confirmed hypothyroidism as the most likely diagnosis. Cisapride was added to the existing symptomatic treatment. Levothyroxine sodium liquid was initiated at a dose of 0.03mg/kg SiD. Faecal consistency gradually improved, and the associated tenesmus reduced. The levothyroxine dose was incrementally increased in response to blood sampling undertaken every few weeks. After 5months of treatment the patient had reached 2.7kg and was receiving a levothyroxine dose of 0.02mg/kg BiD, total T4 finally having reached the normal range. Cisapride and lactulose were administered as needed. Castration was delayed to 12months of age, when he weighed 3kg. The levothyroxine dose was adjusted for growth - which was slower than normal - and monitored with regular blood tests, aiming for high-normal total T4/low TSH at 4-6hours post-dosing. By 4 years’ old he had reached 5kg with a BCS of 7/9 (!) and was still receiving 0.02mg/kg BiD levothyroxine, now in tablet form.

Statement: Impact/ Clinical Significance

CFH is rare, but should be considered a differential diagnosis for any young kitten presenting with persistent constipation. Delayed growth was an unsurprising feature of this case, but the longer-term skeletal and neurological concerns previously cited¹, were perhaps largely avoided due to early diagnosis and treatment. Mild intermittent dermatitis (responsive to symptomatic treatment) and persistent gingivitis developed, the latter progressing and necessitating dental extractions. Further clinical sequelae may come to light as the patient gets older, however he is currently reported happy and well by his owner, who has relocated but kept in touch and kindly gave her permission for this case to be shared.

Thanks go to Dr Selda Curtseit DVM MSc PhD MRCVS, employed at our local external lab at the time they received the blood sample and clinical history, and who suggested testing for hypothyroidism. 

Thanks also go to Martha Cannon, Danielle Gunn-Moore, Paul Higgs, Ellie Mardell, Nicki Reed and Severine Tasker for their helpful advice regarding treatment and prognosis at the time of diagnosis, in November 2018.

¹Brett Wasik DVM DACVIM (SAIM) 24.03.2016 Congenital Hypothyroidism