Does all hormones need to enter the blood stream to be able to affect a cell?

Not all hormones need to enter the bloodstream to affect a cell. While many hormones, such as insulin and adrenaline, circulate in the blood to reach their target cells, some hormones can exert their effects locally through paracrine or autocrine signaling. For instance, local signaling molecules can influence nearby cells without entering the bloodstream. Therefore, the mode of action depends on the specific type of hormone and its mechanism of action.