Hi rose, Iam not sure I understand what you mean. I was diagnosed with hypothyroid about 3 years ago. He is a great doctor, but after being on synthroid for a year and 1/2, I was back in his office complaining of low energy and other things. But it seems once he diagnosed the hypo thing that was it. He would check my levels and they are all good. He says well not everything is about the thyroid maybe your stessed or..... I love this doctor, but not once did he ever mention b12 levels. When it comes the endo system hes one of the best. His name is on the list if you go online and look up info about doctors and the new ranges. Anyway Iam rambling now... THis happens way to often I was going to make a point here I completly forgot what is was. You mentioned an underlying thryroid problem, do you mean other then the aready existing hypo? What else is there? I thought you where eith hypo or hyper?