Can a B12 deficiency cause a problem with your thyroid?

I am not so sure that B12 deficiency causes thyroid problem BUT someone with a thyroid problem is more than likely to be B12 deficient.
A lack of B12 usually effects your nerves and stress level and memory more than anything from what I have seen.
Vitamin B12 is hard for some peoples body to absorb properly. If they are not absorbing it properly they need to talk to the dr about getting B12 shots. It is the only way people with the problem can absorb it. My grandmother's memory was going and I kept telling my mom about B12 shots. She ended up in a nursing home with Alzheimer's and they had to give her B12 shots.
She should go to the doctors and get her B12 level, thyroid and liver checked.
If her body is absorbing B12 properly then take sublingual B12
Also a lack of iodine will cause a thyroid problem. Do they use iodized salt and eat sea food?
They might want to get their iodine level checked too.