Abstract
A 62-year-old man became aware of his high blood glucose level during a health checkup in 2002, but the condition was left untreated. In July 2013, with the appearance of thirst, polydipsia and polyuria, he was drinking more than 3 l of water and soft drinks a day. When he consulted a neighborhood doctor, he was diagnosed with diabetes mellitus (DM) according to the results of a fasting plasma glucose of 150 mg/dl and HbA1c of 7.5 %. He was medicated with an antidiabetic drug, however, his symptoms remained. He was admitted to our hospital for further examination. He was finally diagnosed with central idiopathic diabetes insipidus (DI). The patient's serum IgG4 was high (433 mg/dl), and DI was suspected to be associated with IgG4-related disease. His symptoms improved by the oral administration of desmopressin. However, although his plasma glucose level improved, the patient continued to have impaired glucose tolerance. The complication of central DI and type 2 DM is very rare, and in most reported cases, the diabetes state improved after treatment for central DI. Multiple factors including dehydration, hyperosmolarity, dysfunction of the V1 receptors and increased soft drink consumption may be associated with the aggravation of glycemic control.
