Hormones bind to specific proteins (called hormone receptors) in the target tissues and produce effect on them. Receptors are specific.

There are two types of receptors:
(i) membrane bound receptors - hormone receptors present on the cell membrane of the target cell
(ii) intracellular receptors - receptors present inside the target cell

Hormone-receptor complex is formed on binding of hormone to the receptor. This complex leads to certain biochemical changes in the target tissue.

Hormones that interact with membrane-bound receptors generate second messenger (which do not enter the target cell). These regulate cellular metabolism mostly by regulating gene expression or chromosome functions.