Endocrine Abstracts

A 64 year-old Caucasian woman was admitted with a five-week history of lethargy, sore throat and dyspnoea, and diarrhoea with intermittent rectal bleeding, with a collapse on the morning of admission. She presented to the Emergency Department via ambulance and was found to be profoundly unwell with cold sepsis. She had a background of rheumatoid arthritis treated with weekly methotrexate, with no history of diabetes or long-term steroid-use. Blood tests revealed pancytopaenia, secondary to methotrexate (stopped on admission), acute kidney injury and severe metabolic acidosis. CT angiogram demonstrated lung base ground-glass changes, the patient had been double-vaccinated for COVID-19 and all COVID swabs were negative. Despite receiving a course of intravenous Tazocin, respiratory symptoms worsened. On the advice of our local Respiratory and Infectious Diseases teams, treatment-dose co-trimoxazole (at 120 mg/kg/day in split doses) with a short course of prednisolone 30 mg daily was commenced for suspected Pneumocystis pneumonia from being immunocompromised. Over the next ten days she developed new-onset confusion, reduced appetite and a random blood glucose at midday was found to be 1.2 mmol/l. After treatment, hypoglycaemia recurred and persisted despite repeated intravenous dextrose boluses and glucagon injection. Blood glucose improved only with continuous 10% dextrose infusion. Causes were explored – a normal 9 am cortisol ruled out adrenal insufficiency, and a recent CT scan showed no pancreatic or other intra-abdominal pathology. When serum glucose was 3.3 mmol/l, C-peptide measured was found to be inappropriately high (5175 pmol/l). A literature review revealed rarely Co-trimoxazole can cause hypoglycaemia at higher doses, hence this medication was stopped. Hypoglycaemia subsequently resolved and confusion improved within 48 hours. Co-trimoxazole is biochemically similar to sulfonylureas, mimicking their action on pancreatic beta-cells. Endogenous insulin hypersecretion resulted in raised C-peptide levels during the hypoglycaemic phase. As Co-trimoxazole is renally excreted, when renal function is impaired it accumulates further, with exacerbation of side effects such as protracted hypoglycaemia, especially at higher doses, as in our case. Hypoglycaemia will likely resolve after a 24-48 hour washout period, especially if renal function improves back to baseline. We recommend awareness of hypoglycaemia risk with high-dose co-trimoxazole treatment and blood glucose monitoring for inpatients especially in the setting of renal impairment.