Why do some hormones need to trigger a 'second messenger' to activate a target cell?

Some hormones need the secondary messenger because

Some hormones need the secondary messenger because

Which of these hormones uses cAMP as a second messenger ?

Second messengers are activated in response to

Second messengers are activated in response to

Why are hormones referred to as chemical messengers?

(a) Who is termed as first messenger and second messenger in the target cells ? (b) How do protein hormones act on target cells ?

_____acts as second messenger in the cell.