Adrenal cells from rats without a pituitary gland are more sensitive to a hormone called adrenocorticotropic hormone compared to cells from rats with a pituitary gland. This means that these cells need less of the hormone to start producing a substance called 3',5'-adenosine monophosphate. This increased sensitivity also leads to a stronger response in producing steroids when exposed to the hormone within the first 2 days after the pituitary gland is removed.