Question: The negative feedback regulation of thyroid hormone is as follows: 
 Options:  <1> High concentrations of circulating free T3 and T4 that elevate HRT. <2> High concentrations of circulating free T3 and T4 that raise TSH. <3> High concentrations of circulating free T3 and T4 that decrease TRH. <4> Decreased TRH that elevates TSH. <5> Decreased TSH that elevates HRT.
3