EN08 - Total Thyroxine and Thyrotropin Concentrations During the Recovery from Non-thyroidal Illness in Dogs: Preliminary Results

Abstract: Background Non-thyroidal illnesses (NTI) can affect serum total thyroxine (tT4) and thyrotropin (TSH) concentrations in dogs.

Hypothesis and objective To longitudinally evaluate tT4 and TSH in dogs in course of acute NTI and during the recovery phase.

Animals Ten euthyroid client-owned dogs from a hospital population.

Methods Prospective, longitudinal, observational study. Dogs hospitalized due to acute NTI were enrolled. Serum tT4 and TSH concentrations were measured at the hospital admission (T-1), every 72h during the hospitalization, at the discharge (T0), at 3,7,14, and 21 days after discharge (T1,T2,T3,T4, respectively). Hypothyroidism was excluded based on tT4 within reference interval (WRI) and absence of clinical signs at T4.

Results Mean (±SD) tT4 was 22.9 (±6.7), 28 (±9.3), 31.3 (±9.8) mmol/L and mean(±SD) TSH was 0.22 (±0.17), 0.15 (±0.07), 0.31 (±0.19) ng/dL at T-1,T0,T4, respectively. At T-1, tT4 was WRI in all dogs and TSH was increased in 1/10 (10%) dogs. One out of 10 (10%) dogs showed low tT4 during the hospitalization. Both tT4 and TSH were WRI in all dogs at T0. Four out of 10 (40%) dogs showed high TSH at least once during the follow up period. TSH was increased in 2/10 (20%) dogs at T4. tT4 and TSH comparison between different time-points showed no difference.

Conclusions and clinical importance Serum TSH concentration increases above the upper reference limit in some euthyroid dogs during the recovery phase from NTI. This increase is detectable up to at least 21 days after the resolution of the acute phase of the disease.