Sentence:  At the present time we do not know by what biochemical mechanism TSH acts on the thyroid , but for <WSD>bio-assay</WSD> of the hormone there are a number of properties by which its activity may be estimated , including release of iodine from the thyroid , increase in thyroid weight , increase in mean height of the follicular cells and increase in the thyroidal uptake of * * f . 
Meaning of the word marked with <WSD> tags:  appraisal of the biological activity of a substance by testing its effect on an organism and comparing the result with some agreed standard