Increased serum leptin and insulin concentrations in canine hypothyroidism

Serum concentrations of leptin and insulin were compared between gender-matched hypothyroid (n = 25) and healthy (n = 25) client-owned dogs within comparable age and body condition score (BCS) ranges. Fasted blood samples were collected from each dog and analysed for glucose, cholesterol, triglyceride, leptin and insulin concentrations. Leptin and insulin concentrations were significantly higher in the hypothyroid compared to normal dogs (P = 0.006 and P = 0.001, respectively) following adjustment for potential confounders. A nearly significant (P = 0.051) interaction with BCS was found in the association between hypothyroidism and leptin. Leptin concentrations were significantly higher in hypothyroid dogs compared to normal dogs, in separate analyses for BCS 6 (P = 0.036) and 7 (P = 0.049). There was no significant difference in glucose concentration between the hypothyroid and normal groups (P = 0.84) following adjustment for BCS. This study showed that canine hypothyroidism is associated with increased serum leptin and insulin concentrations, neither of which may be attributed to obesity alone.