Studies on Canine Thyroid-stimulating Hormone (cTSH), Total Triiodothyronine (TT3), Total Thyroxine (TT4) and Free Thyroxine (fT4) in Healthy and Hypothyroid Dogs

Background: The study aimed to measure canine thyroid-stimulating hormone (cTSH) levels and their relationship with total triiodothyronine (TT3), total thyroxine (TT4) and free thyroxine (fT4) in healthy and hypothyroid dogs. Methods: The study involved 77 dogs, with 67 healthy and 10 hypothyroid. The serum concentration of cTSH was measured using a canine-specific TSH-ELISA kit, while TT3, TT4 and fT4 were measured using RIA kits. Result: The Mean serum concentration of cTSH, TT3, TT4 and fT4 in healthy dogs was 2.03±0.01 µIU/ml, 0.85±0.04 nmol/l, 20.81±0.79 nmol/l and 12.59±0.35 pmol/l, respectively. Mean cTSH, TT3, TT4 and fT4, concentration of hypothyroid dogs was found to be 2.16±0.03 µIU/ml, 0.93±0.07 nmol/l, 9.01±0.69 nmol/l and 5.87±0.82 pmol/l, respectively. Interquartile range (i.e. 25th to 75th percentile) for thyroid hormone (cTSH, TT3, TT4 and fT4) in healthy dogs (n = 67) were 1.96-2.11 µIU/ml, 0.64-0.96 nmol/l, 16.73-25.00 nmol/l and 11.00-14.40 pmol/l, respectively and for hypothyroid dogs (n = 10) were 2.09-2.22 µIU/ml, 0.73-1.12 nmol/l, 7.50-10.29 nmol/l and 4.35-7.45 pmol/l, respectively. A significant difference (P less than 0.05) was recorded in healthy and hypothyroid dogs in cTSH, TT4 and fT4.