Sentence:  A study of their activity on thyroglobulin has shown that <WSD>thyroxine</WSD> is not preferentially released and that the degradation proceeds stepwise with the formation of macromolecular intermediates ( Alpers , Petermann and Rall , 1956 ) . 
Meaning of the word marked with <WSD> tags:  hormone produced by the thyroid glands to regulate metabolism by controlling the rate of oxidation in cells