Which class of hormones acts by means of a second-messenger system
A)catecholamines
B)proteins
C)steroids
D)thyroid hormones

Question

Quizplus · Accepted Answer

Both catecholamines (such as epinephrine and norepinephrine) and proteins (such as insulin and growth hormone) act by means of a second-messenger system. This means that they bind to a receptor on the cell membrane, which then activates a second messenger within the cell (such as cyclic AMP or calcium ions) that ultimately triggers a cellular response. Steroids and thyroid hormones, on the other hand, bind directly to intracellular receptors and do not require a second messenger system.

Which Class of Hormones Acts by Means of a Second-Messenger