Gliclazide Challenge Testing as an Alternative Diagnostic Tool for Hepatocyte Nuclear Factor-1-Alpha Maturity Onset...

Hepatocyte nuclear factor-1-alpha monogenic diabetes (HNF1-alpha DM), formerly known as maturity-onset diabetes of the young type 3 (MODY 3), is often misdiagnosed as type 1 or type 2 diabetes. In regions where genetic testing is unavailable, alternative diagnostic approaches are needed.

A 20-year-old woman was initially diagnosed with type 1 diabetes after an incidental finding of hyperglycaemia. Despite adherence to treatment, she experienced recurrent hypoglycaemia on basal-bolus insulin, receiving over 2600 injections in 8 years. Autoantibodies were negative, C-peptide levels were preserved, and her estimated probability of MODY exceeded 10%. While awaiting genetic testing, she underwent a "glicazide challenge test", which showed a marked stimulatory response in blood glucose and C-peptide levels. Subsequent testing confirmed HNF1-alpha MODY. Insulin was stopped, and she was started on low dose gliclazide, achieving excellent control with minimal hypoglycaemia.

This case demonstrates the gliclazide challenge test's potential as an alternative diagnostic and therapeutic tool in suspected maturity-onset diabetes of the young when genetic testing is limited.

Young patients with atypical diabetes (negative autoantibodies, preserved C-peptide, recurrent hypoglycaemia on insulin) should prompt consideration of monogenic diabetes, and the Exeter maturity-onset diabetes of the young calculator is a valuable screening tool for clinicians.A gliclazide challenge test with serial C-peptide measurement can provide a simple, functional assessment of sulfonylurea sensitivity, supporting the diagnosis of maturity-onset diabetes of the young, in centres where genetic testing is limited or delayed.Early recognition of maturity-onset diabetes of the young allows safe transition from insulin to sulfonylureas, preventing years of unnecessary injections, reducing hypoglycaemic episodes, and improving long-term quality of life.