Vitamin B12 & Hypothyroidism: What You Must Know Symptoms of vitamin b12 deficiency. Studies show that low levels of vitamin b12 may be more common in people with hypothyroidism. Vitamin b12 is also involved in making and metabolizing thyroid Methyl B12 for Autism The Autism Community in Action HASHIMOTO'S THYROIDITIS What is Hashimoto's thyroiditis? Hashimoto's thyroiditis is an autoimmune condition in which the immune system attacks the thyroid gland. Over time, this can damage the thyroid and