Although thyroid hormone results from sighthounds frequently lie outside standard laboratory reference intervals (RIs), limited information is available within individual breeds, including salukis. The aims of this study were to document thyroid hormone concentrations in salukis; calculate breed-specific RIs; and determine effects of reproductive status, age, and activity.

Blood samples were collected, allowed to clot, centrifuged, separated within 2 hours of collection, and frozen at -20°C until assays were performed. Total thyroxine (T4), free T4 (equilibrium dialysis), total triiodothyronine (T3), free T3 and thyroid stimulating hormone (TSH) concentrations were measured using validated assays. Median and RI (2.5th-97.5th percentiles) were reported. Mann-Whitney testing was used to compare results between groups and Spearman's rank correlation testing to assess correlations with age.

Blood samples were collected from 283 salukis: 154 were female (15 neutered) and 129 male (6 neutered); age ranged from 12-167 (median 61) months; 49 were coursing and 234 non-performing.

Median (RI) concentrations of total T4 (n = 282), free T4 (n = 216), total T3 (n = 281), free T3 (n = 271) and cTSH (n = 282) were 13 (1-40) nmol/L, 12 (2.0-30.3) pmol/L, 1.0 (0.4-2.1) nmol/L, 4.0 (2.8-6.5) pmol/L and 0.18 (0-0.86) ng/mL, respectively. Total and free T4 concentrations were significantly (p<0.0001) lower in males than females. Total T4, free T4 and TSH concentrations were correlated with age (p = 0.037, r = -0.12; p = 0.0009, r = -0.22; p<0.0001, r = 0.35; respectively. TSH concentrations were significantly (p = 0.03) higher in non-performing than performing dogs.

Breed-specific RIs should be used when interpreting thyroid hormone profiles from sighthounds. The diagnostic utility of these tests requires further assessment.