Interactions among hormones can be characterized as having synergistic, permissive, or antagonistic effects.
Hormones that work in conjunction with one another are described as synergistic.
epinephrine and norepinephrine interact to increase heart rate
estrogen, prolactin, oxytocin, and cortisol all work together in lactation
Permissive effects occur when one hormone causes an increased sensitivity or greater activity in another hormone.
glucocorticoids increase activity of cathecholamines
uterine estrogen increases sensitivity to progesterone
Antagonistic effects are when hormones work against each other.
high levels of estrogen during pregnancy curb prolactin
insulin and glucagon inhibit each other