Feedback Loops
Multiple hormones involved in coordinating homeostatic responses that keep their conc. at optimal physiologic levels
Feedback loops control _ or_ in hormone production (e.g. _ T4 present in order to reduce _ release of TSH or TRH to prevent further synthesis of the hormone).
Lack of negative feedback would result in hyperfunctioning of the gland (e.g. Graveís disease).
Conversely _T4 must be available to _ release of TSH and TRH to effect further hormone synthesis.