Yes, I have relatively mild gastritis as the result of taking ibuprofen when I broke my leg. I also am hypothyroid.
Many hypothyroid patients have low stomach acid which results in poor absorption of nutrients and can lead to outright deficiency of B12 and other nutrients. Omeprazole and the other acid inhibitors have the same effect, of course. Low stomach acid also causes heartburn because the lower levels of acid fail to trigger the closing reflex of the sphincter at the bottom of the oesophagus, so the food/acid mixture leaks out of the stomach, and it is quite acid enough to cause pain and erosion. Sadly, the average GPs response is to prescribe PPIs.
Omeprazole didn't make much difference to my gastritis, so I refused it. The consultant was a bit upset, but I decided that I would manage by diet alone. I have found that certain foods cause my symptoms, and they are not 'acid' foods, so much as irritants. No crushed peppercorn crusts for me! I also get heartburn from corn and gluten free products (I was already GF).
You can evaluate your stomach acid with a simple home test decribed here
www.stopthethyroidmadness.com/stomach-acid/
After that I think its probably a matter of finding your trigger foods and avoiding them. Some people find nightshades and citrus a problem, the only thing that I have found other than pepper and other obvious irritants is nuts.
I also found zinc carnosine really helpful when I had my last flare. For me much better than DGL or slippery elm. In Japan zinc carnosine is the preferred method of treating ulcers and gastritis, and doesn't affect stomach acid. I doubt the Japanese stomachs are that much different to ours! Mind you, in Japan they supplement B12 at levels that we would be told we are normal. So they are certainly different, and many of us would say more enlightened.
Have you had your thyroid levels checked? Folate? vitamin D? They need to be not just 'normal' but optimal. And you should also be screened for coeliac disease which can cause similar symptoms. Sadly, autoimmune diseases tend to hunt in packs, so if you have one, the risk of others is higher.
The Pernicious Anaemia Society, and Thyroid UK both have boards on HealthUnlocked.com - very helpful and supportive communities. You could post your latest test results there, and there will be someone with relevant experience and knowledge, I am sure. There is also a Gastritis Support group on Facebook. Its mostly people venting about their pain and distress, but there are occasional gems of information (and sometimes its useful to vent yourself!).
