• Key words;
  • Canine;
  • Euthyroid sick syndrome;
  • thyroid;
  • critical patients;
  • mortality.


Alterations in thyroid indices in critically ill dogs were studied retrospectively to determine the incidence of the euthyroid sick syndrome and to assess its prognostic relevance to survival. Sixty-seven dogs were classified as euthyroid bases on a TSH stimulation test. Forty-one of 67 (61%) of the euthyroid dogs had low baseline serum T4 concentrations (<1.5 ug/dl) and 38 of 67 (56%) of the euthyroid dogs had low baseline serum T3 concentrations (<75 ng/dl). There was no significant difference between either the baseline or the post-stimulation serum T4 concentrations when values of dogs that survived were compared with those that died. There was, however, a significant difference (P<0.05) between both the baseline and the post-stimulation values for T3 when survivors (100.3± 81 ng/dl, 143± 66 ng/dl) and non-survivors (64.2 ± 17.1 ng/dl, 96.6 ± 38.3 ng/dl) were compared. The euthyroid sick syndrome occurs commonly in critically ill dogs. Further, the extent of depression of serum concentrations of T3 may be correlated to mortality.