Mechanism of Hormone Action: A Hormone is a tiny chemical messenger, travelling along with the bloodstream. It exists to maintain internal balance or in other words, keeps the human body in a state of homeostasis.

Types of Mechanism of Hormone Action

• Fixed membrane receptor mechanism
• Mobile receptor mechanism

Fixed Membrane Receptor Mechanism

This type of mechanism is shown by the water-soluble hormones that are amines or proteins in composition such as the growth hormone, oxytocin, ADH, etc.

These hormones can’t pass through the lipid membrane. They have their target receptor on the cell membrane to which the hormone binds.

When the hormone binds on the specific target receptor, the enzyme adenyl cyclase in the cell membrane is activated. This helps in the production of cyclic AMP (cAMP).

cAMP acts as the secondary messenger. It diffuses through the cell membrane and activates several enzymatic reactions to cause biochemical changes.

The target cell responds to these changes and cAMP is deactivated by the enzyme phosphodiesterase.

Mobile Receptor Mechanism

This type of mechanism is shown by lipid soluble hormones such as fatty acids and steroids that can easily pass through the plasma membrane.

They possess intracellular receptors. The hormones bind to the target receptor that activates the enzymatic activity of the cell to bring about biochemical changes.

Transcription of DNA is initiated by the hormone-receptor complex.

The mRNA is translated into protein. This protein causes biochemical changes inside the cell.

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By Team Learning Mantras