What happens after a hormone binds to its receptor?

When a hormone binds to its specific receptor, it forms a hormone-receptor complex that initiates a chain of chemical responses within the target cell to produce a physiological effect. The specific mechanism depends on the type of hormone and the location of the receptor:12

• Cell Surface Receptors: Protein and peptide hormones typically bind to receptors on the cell membrane. This binding often triggers the generation of second messengers (such as cAMP, inositol phosphates, or calcium ions) within the cell, which then activate enzymes or other proteins to alter cellular activity. In some cases, the receptor directly controls ion channels to change the cell's electrical state.132
• Intracellular Receptors: Steroid hormones and thyroid hormones pass through the cell membrane to bind with receptors located in the cytoplasm or nucleus. This complex often interacts directly with DNA to stimulate or inhibit the synthesis of specific proteins, a process that generally occurs more slowly than surface-level signaling.12

These actions may result in enzyme activation, changes in gene expression, or the secretion of other hormones.12