How do hormone receptors determine which tissues a hormone affects?

Hormone receptors determine which tissues a hormone affects through their high degree of specificity and selective expression within the body. Because hormones circulate throughout the bloodstream, they encounter many different cell types, but they can only exert an effect on tissues that possess the specific receptors designed to bind to them.1

This selectivity is governed by two primary factors:

• Specific Affinity: Each receptor has a strong, highly specific chemical affinity for a particular hormone. A hormone acts only on tissues where these matching receptors are present, ensuring that hormonal actions are targeted rather than general throughout the body.1
• Selective Gene Expression: A cell’s ability to respond to a specific hormone is fundamentally influenced by its ability to express only certain receptor genes. If a cell does not express the gene for a specific receptor, it remains unresponsive to that hormone, regardless of the hormone's concentration in the blood.2

Once the hormone binds to its specific receptor, it forms a hormone-receptor complex that triggers a chain of chemical responses within the target cell, such as enzyme activation or the regulation of gene expression.13