Endocrine Abstracts

Hyperglycaemic hyperosmolar state (HHS) is a common medical presentation, typically occurring in older patients with Type 2 diabetes mellitus. Mortality rates have been reported to be up to 60%. Precipitating factors include dehydration, sepsis, cardiovascular disease and drugs. Here, we describe a rare case of HHS, likely to have been precipitated following the development of lithium-induced nephrogenic diabetes insipidus (DI).

A 62-year-old female presented with lethargy, confusion and reduced mobility. Her past medical history included bipolar disorder treated with lithium for more than 10 years. She was noted to be persistently hypernatraemic with sodium >170 mmol/L despite intravenous fluids. However on day ten of admission, her blood glucose was noted to be 25 mmol/L with serum osmolality of 398 mmol/L. She was reviewed by the endocrinology team and deemed to be in HHS. Treatment was commenced with a fixed rate insulin infusion and 0.9% saline. CT head excluded intracranial pathology. Over the forthcoming few days in the Intensive Care Unit, despite a fall in blood glucose, her plasma sodium remained persistently elevated despite intravenous fluids. She remained polyuric with an increasing plasma osmolality and a reduced urine osmolality. This prompted the consideration of nephrogenic DI as a concomitant pathology. Overnight water deprivation confirmed the diagnosis of DI. Amiloride with hydrochlorothiazide was started as treatment for nephrogenic DI, and a subsequent improvement was observed with falling serum osmolalities and plasma sodium. Her plasma glucose concentrations remained stable on oral anti-hyperglycaemic agents.

Our case illustrates HHS, associated with severe and life-threatening water depletion and hypernatraemia, to be the presenting feature of nephrogenic DI. Following recovery from hyperglycaemia, a persistent polyuric and hyperosmolar state should prompt consideration of DI. It is rare for the two conditions to co-exist; however it is an important differential to consider, so that appropriate therapy is initiated promptly.