Background: GCK-MODY is an autosomal dominant form of diabetes. Heterozygous inactivating mutations in GCK result in mild, persistent asymptomatic hyperglycemia due to a glucose sensing defect. It is reported that GCK-MODY is not associated with significant diabetic complications and that pharmacological therapy does not alter glycemia.

Aim: We aimed to establish the percentage of GCK-MODY patients on pharmacological therapy and its impact on their glycemic control, along with the incidence of diabetic complications.

Methods: 32 patients were identified. Glycemic tolerance was established using an OGTT. Treatment details were recorded. Diabetic complications were identified. Following genetic diagnosis of GCK-MODY pharmacological therapy with Metformin was discontinued in 7 of 11 patients. HbA1c before and 6 months after discontinuing therapy was compared. Data was analysed in Microsoft Excel and Stata 4.2.

Results: Treatment at diagnosis included, insulin (4), sulfonylurea (2), DPP-4 (5), Metformin only (11), and diet alone (15). Mean HbA1c at MODY diagnosis in all patients was 45.7+/-4.4 mmol/mol. 7/11 patients discontinued metformin only and had no change in glycemic control HbA1c(46.8+/-3.5mmol/mol pre vs. 47.9+/-3.0 mmol/mol post; p=0.38). 40.6% of those screened had background diabetic retinopathy not requiring treatment; 0.03% had Microalbuminuria and 0.125% had CAD.

Conclusion: Prior to genetic diagnosis of GCK-MODY, patients were frequently misdiagnosed, with 50% on pharmacological therapy. Discontinuation of metformin resulted in no deterioration of glycemic control indicating that metformin therapy had no impact on the glucose sensing defect. Background diabetic retinopathy was the commonest complication, but did not require treatment.


S. Boyd: None. M.M. Byrne: None.

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