Bilateral femoral capital physeal fractures in an adult cat with suspected congenital primary hypothyroidism

A 4-year-old, neutered male European shorthair was presented for evaluation of right hind limb lameness. Radiographs revealed bilateral femoral capital physeal fractures, widened vertebral growth plates and constipation. Physical findings included lethargy, mental dullness, mild hypothermia, retarded growth, pharyngeal stridor, moderate muscle atrophy of pelvic limbs, hair coat abnormalities, and lack of defecation and urination. A thyroid panel revealed thyroid hormone values below detection limits and high thyroid stimulation hormone values. A presumptive diagnosis of congenital primary hypothyroidism was made, however also an early onset acquired primary hypothyroidism could not be ruled out. Results of the insulin-like growth factor (IGF-1) and the parathyroid hormone as well as an adrenocorticotropic hormone stimulating test were normal. A bilateral femoral head and neck excision was performed. Levothyroxine supplementation was started at a dosage of 50 µg (11 µg/kg) BID and later adjusted to 100 µg (22 µg/kg) BID based on total thyroxine concentrations. The tomcat showed full clinical recovery and normal clinical behaviour. The case shows that primary hypothyroidism may be considered in cats presented with femoral capital physeal fractures.