GCK MODY commonly misdiagnosed as GDM
Hi everyone,
I just wanted to make this post in case it could help one person get the right treatment.
I gave birth in July of last year after dealing with a stubborn, but not severe, per se, case of GD. My fastings would not move from 98-110, insulin might work for a day or two, but they would always climb back up very predictably. I ate a low carb diet (I know that the safety of this is not quite decided upon, but I did a lot of research and self ed on it and felt the risks of eating not a ton of carbs were less worrisome than the risks of having consistently high BG, and my care team was comfortable with this), and although my meals would technically be in range, they would be much higher than what you would expect in a typical person (Ex. 115 at 2 hours pp). The highest reading I ever got was 170 1 hour after a very high glycemic index meal, which is also not really consistent with insulin resistance. I actually remember saying to by husband “it’s like my insulin sensitivity works just fine, but I start at a higher baseline and can’t bring that baseline down, but that’s not how diabetes works.“ little did I know, there actually is a monogenic condition called GCK-MODY that works exactly like this.
My dad was (mis)diagnosed with type 2 16 years ago, while thin, active and healthy. he was always told “well thin people can develop insulin resistance too,” which is totally true! But his diabetes behaved incredibly strangely. It never improved or went into remission, despite medication, increasing exercise and limiting carbs progressively, but also never progressed, and his a1c has never left the 6.5-7% range. His fasting glucose has been 112 since he was diagnosed. Diabetes is a progressive disease, so this was very strange. He also has optimal fasting insulin levels, for those who don’t know, in someone with a high fasting BG due to insulin resistanc, fasting insulin is very high because your body is trying to compensate for the insulin it is not using.
i was diagnosed with prediabetes as a reasonably healthy young woman (another red flag) my a1c was 5.9. It’s been 5 years since then, and I have lost some weight, dedicated myself to nutrition and a wide variety of exercise, been on metformin for over a year, and greatly limited any lifestyle patterns that worsen IR, and my A1C remains at 6%. I also confirmed that my fasting insulin is optimal, despite a fasting BG of 110.
ANYWAYS, this is all to say, if any of this sounds familiar to you, I would suggest looking into MODY. MODY is a group of genetic mutations that in themselves are sufficient to cause high BG. Many of them have to do with beta cell dysfunction and are functionally very similar to T1 or 1.5, but one subtype, GCK MODY, (the one my dad and I just learned through genetic testing that we have), is a “typo,” so to speak, in the gene that codes for the creation of the enzyme glucokinase, which helps your pancreas sense when your blood sugar is elevated and you need to start secreting insulin. This results in lifelong, mild, non progressive, elevated blood sugar. It notable does NOT respond to treatment, which is actually recommended heavily against due to the emotional and financial impact of treating a misunderstood disease with therapy does not work. The great thing is, though, that it is not thought to cause an increased risk of any of the health risks that are normally associated with high blood sugar, like heart disease and neuropathy.
onto pregnancy, it is thought that at least 1 in 100 mothers with GD actually have undiagnosed GCK-MODY, compared to 1 in 1,000 in the general population. A recent study actually found that in expecting patients with a BMI of 21 or lower and a fasting glucose regularly above 99, only 2.7 needed to be tested to find 1 case of GCK-MODY! It is incredibly important to identify these patients, because treatment for GCK-MODY in pregnancy is very different from typical GDM, and depends on the genetic status of the baby, who has a 50% chance of inheriting the mutation.
Anyway, if anyone finds my situation relatable, I would totally consider trying to undergo genetic testing. The UChicago Monogenic Diabetes Registry has really great resources and is actively trying to find better solutions for pregnant patients with any form of MODY. i also want to say that even if this story isn’t yours, one of the most frustrating things about navigating gestational diabetes was the stigma ad the assumptions made about those with it. Diabetes is a very strange disease and there’s still a lot we don’t know about it (especially T2). Hope everyone on here is able to find the answers they need.