The hormone epinephrine binds to ß adrenergic receptors on smooth muscle cells of the bronchioles, causing them to dilate (increase in diameter). Thyroid hormone is essential for the synthesis of ß adrenergic receptors; therefore, in the absence of thyroid hormone, epinephrine cannot trigger bronchodilation. This concept if known as .

The correct answer is "permissiveness".

Explanation:

The missing options of the question are:

permissiveness

synergistic effect

antagonism

additive effect

The correct answer is "permissiveness",

In biology, a permissive effect is defined as the effect that one hormone has enabling that a second hormone to exert its biological activity. Thyroid hormone has a permissive effect on the hormone epinephrine, by synthesizing ß adrenergic receptors, it enables the hormone epinephrine binds to them and cause the cells of the bronchioles to dilate.