B12 and High levels of Serum gastrine

[mickeymouse42]

The link between low B12 and the Serum gastrine test is discussed at the bottom of the page:

pernicious-anaemia-society....

High levels of the gastrine hormone are a sign of low levels of stomach acid - anyone know why this is the case?

I guess that increasing B12 levels via injections or oral treatment doesn't lower the level of the gastrine hormone or increase the levels of stomach acid?

[fbirder]

Yup, I know.

Gastrin is a hormone, released when you eat something. It does various things, one of which is to tell the gastric parietal cells (GPCs) in the stomach to release stomach acid. This acid lowers the pH of the stomach, which tells the body to stop making gastrin. It's a negative feedback loop.

However, if you have Autoimmune Metaplastic Gastric Atrophy (AMGA) which is the root cause of Pernicious Anaemia, then you do not have GPCs, so you have no stomach acid (achlorhydria) so your stomach pH does not get lowered, and gastrin production is not switched off.

You keep on producing gastrin, and that means you have high levels of gastrin in the blood - hypergastrinaemia.

So the high gastrin is caused by the same thing as the low B12. Raising B12 levels cannot affect the lachlor syria or the hypergastrinaemia.

It's a pretty good sign on having PA, as long as other possible causes (taking lots of antacids, PPIs, etc.) are eliminated. There are also Type 2 neuroendocrine tumours (NETs) that can raise gastrin, but they will not be associated with low B12 or any of the symptoms of a B12 deficiency.

Hypergastrinaemia can cause problems, especially Type 1 NETs. These are rare and are indolenet - they tend to sit around a do nothing. I've had them for 5 years and I just have a gastroscopy to keep an eye on them.

Edited by Admin

Achlorhydria and Gastrin

[mickeymouse42 in reply to fbirder]

Thanks again for another very helpful reply.

If you don't have PA but low B12 because bacteria are feeding on the B12, would the same gastrin feedback loop apply?

I get confused when we talk about things with logarithmic scales - I'm a classicist rather than a chemist!

A pH level of 1 is much more acidic than a pH level of 6 so when we say that the stomach acid is being lowered, pH numbers are increasing?

If you had PA and were monitored for pH levels using the Heidelberg pH monitoring test, you would expect high pH levels?

[fbirder in reply to mickeymouse42]

If you don't have PA but have low B12 caused by SIBO (Small Intestine Bacterial Overgrowth) then that will no affect secretion of stomach acid, so will not cause high levels of gastrin.

The higher the level of acid, the lower the pH. A change of 1 pH unit means a tenfold change in the amount of acid (strictly, the amount of hydrogen ions).

The Heidelberg test puts a device for measuring pH into the stomach then adding sodium bicarbonate. That will raise the pH (making it less acidic). Then the time taken for stomach acid to lower the pH back to normal levels is measured. If you had PA then this would take a long time, because little acid will be produced.