Test: Mechanism of Hormone Action - NEET

Steroid hormones, being hydrophobic molecules, diffuse freely into all cells and act within the cell. Steroid hormones enter the cytoplasm of a target cell and bind with specific receptor proteins (mobile). Hormone-receptor complex then diffuses into nucleus and activates specific genes to form a new protein. This protein carries out the specific response for a particular steroid hormone.

Hormones recognise target organs by the presence of specific receptor molecules on the plasma membrane of target organs, if these receptor molecules are removed then a hormone will be unable to give any response.

FSH  is a proteinaceous hormone. It does not enter its target cells, thus, it never reaches to cytoplasm. Instead, it binds to the receptor present on the cell membrane and activates a membrane bound enzyme that causes conversion of ATP to cAMP. This then alters the activities of enzymes in the cytoplasm.

Estrogen and testosterone being steroid hormones are soluble in lipids, therefore they can cross the plasma membrane and bind to the cytoplasmic receptors to trigger their action.

Cortisol and testosterone are steroid hormones and are easily soluble in lipids. They regulate gene expression by the interaction of hormone receptor complex with the genome. So, these easily pass through the cell membrane of the target cell and bind to a receptor inside it.