If you've read anything about thyroid hormones (THs), you'll probably know at least three things: a) the complete metabolism is controlled by THs, b) the level of the hormones involved in the complete circuitry (mainly TSH, T3, and T4) are the criteria to define hypo- and hyper-thyroidism, and c) more than 3% of the total population suffer from any of these conditions. Woman are more affected that men in aproximately 10:1 proportion. However many question still to be answered, for example: what about many borderline situations like subclinical hypothyroidism? What about the fast action of changes in thyroid hormone levels? Can we apply the same criteria of normal values range in populations in which the THs levels have been not established? These questions are in discussions and are the principal objective of the collaborative research stablished with the Public Health Department from the Medical Sciences Campus at University of Puerto Rico (UPR). Here in icths we are committed to pursue the major effort applying both basic and translational research in order to understand and unveil these important and essential questions.