I already started a thread about my question in a different subcategory, but there I am asking about what treatment to try out. http://www.tudiabetes.org/forum/t/lean-hba1c-6-1-no-antibodies-low-morning-insulin-c-peptide-now-what/53676
Here I would like to figure out what test to ask for next:
35 y.o. male, physically active, Height: 5' 9.5", Weight: 143, BMI: 20.5
HbA1C: 6.1, has jumped around between 5.7 and 6.1 for the last 3 years. Official diagnosis is preD, obviously, but I agree with some posters here that the distinction between preD and frankD seems quite arbitrary.
Morning BG: almost always between 80 and 100.
2 hr pc bg: between 130 and 140 unless very precise about my meal. My Endo says 140 is higher than what he would like to see.
TSH was tested, and it came out a 1.37 in the range of 0.4 - 4.5.
Everything in my comprehensive metabolic and lipid panel was in the normal range, except for fasting insulin:
Insulin is 1.6, low, where the normal range is 2.0 - 19.6 uIU/mL. As an aside, C-Peptide came out as 0.91 for a normal range of 0.80 - 3.85 ng/mL, so within range, but on the very low side.
Significant history of diabetes in the family. At 40, grandma was diagnosed with full-blown insulin-dependent D, which means that she's been preD for many years before, so similar to where I am now. She had many brothers; many of them ended up blind and without legs; everyone was by and large lean, and most diabetes diagnoses rolled in around 40, so even though I am at HBA1C 6.1 right now, scary things are around the corner if I am not proactive.
Now, I've been reading around, and thin + around 40 + low morning insulin starts looking like LADA for a lot of posters here, so I requested the AB panels from my endo. He's cooperative, so I got them. I got three tests: GAD65, "ISLET CELL ANTIBODY" and "INSULIN AUTOANTIBODY". They all came out negative.
As another aside: I am writing them out instead of using the abbreviations because I am confused about the many abbreviations - they look a lot like each other. For example, I would've thought that "ISLET CELL ANTIBODY" is "ICA", but for some reason the lab (Quest) encoded it as "IA-2", which I thought stood for "insulinoma-associated (IA-2) autoantibodies" (from https://en.wikipedia.org/wiki/Latent_autoimmune_diabetes_of_adults#Autoantibody_panel ). Anyway, I am trying to figure out the precise details of the antibody encodings with my endo.
I bought the 23andMe test back when they were offering the Health Risks service, and for many D genes, I have the genotype that is associated with higher incidence. The three with the highest contribution seem to be: TCF7L2 Genotype CT, CDKAL1 Genotype GG, HHEX Genotype CC. These are associated with "impaired baseline insulin secretion", "impaired first-phase insulin secretion", and "decreased beta cell glucose sensitivity and 30-minute insulin response" (just copying this text from 23andMe)
Anecdotally: when I was a child I was always very thin, and have always had problems putting on muscle mass and keeping it. I now wonder whether this is because my insulin response was always under-performing.
With all that background information:
What test should I ask for next? I am still waiting for results on a Vitamin D deficiency test, but am at a loss as to what has the highest probability of giving me more information.