I just want to share this info from www.thyroidmanager.org: Cobalt. Cobalt inhibits iodide binding by the thyroid.105 The mechanism is unknown. Cobalt deficiency is associated with a reduction in type I monodeiodinase activity and a fall in T3105a while cobalt excess may produce goiter and decreased thyroid hormone production. 105b It is sufficiently active to have been used in the treatment of thyrotoxicosis.106 Also I want to mention that my hair analysis at age 45 showed no elevated cobalt, but at age 51, yes HIGH cobalt...my guess is from B12 supplements. It did not affect me that much...my TSH when not during allergy season is 2.3 (should be below 2.0) but TSH >=2.0 raises cholesterol (which raises blood pressure) so it is something to avoid if at all possible. To be fair I also take a cruciferous vegetable extract and broccoli is supposedly a goiterogen. Life Extension brand and they told me it would not cause problem (but never gave me a reason why). I take the broccoli because it makes my hormones come out right...so to avoid breast cancer. [Hey! I don't know everything! But I don't like that my cobalt came out HIGH on my tests].