Evaluation of an enzymatic immunoassay for free thyroxine determination in canine serum.

Free thyroxine (FT4) and cholesterol were measured in 400 dogs with either suspected hypothyroidism or dermatological signs such that hypothyroidism needed to be ruled out. Hypothyroidism was diagnosed in 68 dogs from the history, physical examination and stated lower reference limit (< 7 pmol/L) for FT4 in euthryoid dogs. Dogs with FT4 concentrations in the range 6-9 pmol/L were finally categorized as hypo- or euthyroid either on the basis of retesting after 2 months or on their clinical response to thyroid replacement therapy over at least 2 months. The enzyme immunoassay evaluated in this paper is considered to be of clinical value and offers many advantages compared with radioimmunoassays.