TGFA and breast adenocarcinoma: The objective of the present study was to verify if the hormone T3, at a physiological concentration, activates the MAPK/ERK pathway (its inhibitor is PD98059) and RNA Polymerase II (its inhibitor is α-amanitin) to modulate the expression of TGFA gene in the MCF7 breast adenocarcinoma cell line in a short time period of 10 minutes (min), 1 and 4 hour (h) of treatment.