difference between tyrosine and l-tyrosine?

well i finally went to the store. i checked out each thing you and everyone else said in answer.... and i was totally suprised. i expected my body to want maca root and selenium. instead i had no response to the maca root and the selenium! but my response to the l-tyrosine and the acetyl-carnitine were off the scale.
i bought the maca root, selenium and zinc anyway, even though i didn't get a hit on them... i'll get muscle tested for them...

i bought l-tyrosine, not tyrosine. doesn't anyone know if this matters as far as the ability to help the thyroid goes?

thx,
Lisa