Abstract: Objective To observe the changes of thyroid function in elderly diabetic patients with hyperglycemic hyperosmolar status (HHS).Methods Clinical material of diabetic elderly pa-tients with hyperosmolar hyperglycemic state from 2009 to 2013 was retrospectively analyzed.Patients were divided into observation group and control group according to the occurrence of hyperosmolar hy-perglycemic state.There were 65 elderly diabetics patients with HHS in observation group and 45 dia-betic elderly patients without HHS in the control group.Results Patients in the observation group had higher levels of blood glucose,serum potassium,blood sodium,blood osmotic and base excess than that in the control group and the difference was statistically significant(P <0.05).The levels of T3 ,T4 and FT4 were lower in the observation group than that in the control group,the difference was statistically significant(P <0.05).After 4 days of treatment,patients in the observation group had higher levels of T3 ,T4 and FT4 than that of prior treatment,so the difference was statistically signifi-cant(P <0.05).Conclusion HHS of elderly diabetic patients could lead to the secondary hypo-function of thyroid and a series of acid base disturbance.With the treatment,the function of thyroid could be recovered.