Endocrine Abstracts

Background: Glucokinase (GCK) is a gene which plays an important role in recognising how high the blood glucose is in the body. It acts as the glucose sensor for the pancreas. Changes in the GCK gene can lead to increases in blood glucose and affected people may be diagnosed with diabetes although this rise in blood glucose is mild and does not need treatment. Glucokinase diabetes is one of familial diabetes types that called MODY (maturity onset diabetes of the young). We report a case was diagnosed with type 1 diabetes during her second pregnancy in 2006 and she was on insulin since. However, her genetic test in 2021 confirmed Diabetes - MODY2 – Heterozygous mutation in GCK.

Case report: 50-year-old female diagnosed with type 1 diabetes during her second pregnancy in 2006 and at that time her ketone levels were high and therefore she was started on insulin. She was commenced on a basal bolus regime during her pregnancy. After pregnancy, she was only on Insulatard twice a day. Her insulin requirements were low so the type of diabetes was revisited in 2010 and at that time the islet cells antibodies were positive and therefore it was agreed to continue to treat her as type 1 diabetes. She was on a small dose of Insulatard and still having hypos and therefore the insulin was stopped in January 2020. Before that she had another set of blood tests done in November 2019 and at that time her islet cell, IA2 and GAD antibodies were all negative. The C peptide level was still in the middle of the range at 0.76 nmol/l. Her HbA1c remained between 39 and 47 mmol/mol since 2009. When she was monitoring blood sugars for a few months after coming off insulin, they were always in the normal range. Her MODY probability score shows the probability of MODY being 15.1%. Her genetic test results show a pathogenic GCK missense variant consistent with MODY2. Her daughter genetic test also confirmed the same variant. It was explained to her that there is no need for any treatment.

Conclusion: Patients with GCK gene variants generally have a mildly raised fasting blood glucose (typically 5.5- 8 mmol/l) and small increment at 2 hours (<4.5 mmol/l) on 75g oral glucose tolerance test (OGTT). Clinicians need to be aware of GCK gene variant and its implications.