I take L-tyrosine because it has been proven important to thyroid support along with selenium. If you don't have high thyroid antibodies you don't need it. If you are not sure, get your thyroid tested: T-4, free
and reverse T-3, both kinds of antibodies. TSH tests are way outdated and only test for the thyroid stimulating hormone from the pituitary gland, it doesn't actually test the effectiveness of the thyroid or circulating active thyroid hormone or autoimmune damage to the thyroid. Using just selenium and tyrosine I have dropped my thyroid antibodies from 1100 to just over 400 in 18 months without synthetic thyroid medications. Healthy normal is as close to zero as possible but at least under 60. I'm getting there (I have other autoimmune conditions).