Permissiveness (biology)
In biology, permissiveness is a biochemical phenomenon in which the presence of one hormone is required in order for another hormone to exert its full effects on a target cell.
Examples
Thyroid hormone increases the number of receptors available for epinephrine at the latter's target cell, thereby increasing epinephrine's effect on that cell. Without the thyroid hormone, epinephrine would have only a weak effect.[1]
Cortisol exerts a permissive effect on growth hormone.