I checked another forum I read, where I remembered having seen a thread on kidney stone formation. First, that KS formation can be a symptom of low vit A and vit K. Wouldn't be much vit A required, but with hypothyroid symptoms, might require pre-formed vit A, not just beta-carotene. This is a summary of supplements recommended --
600 mg elemental magnesium (or whatever just keeps you from diarrhea)
either 500 mg B6 (pyridoxine) or 100-200 mg P5P (pyridoxal 5 phosphate)
vit K, such as Life Extension Super K with 1 mg K1, 1 mg K2 as MK4, and 0.1 mg K2 a MK7
(take 1-3, but start with one to let your body adjust)
no dark sodas
low oxalate (no almonds)
enough water for your body weight
Three people who had stones in their past mentioned keeping stones at bay using primarily magnesium and B6. Vit K is new to the playing field, but very involved in calcium dynamics.