Hormone Types and Signaling Pathways

Peptide Hormones

Water-soluble hormones such as Insulin and Glucagon.

Steroid Hormones

Lipid-soluble hormones such as Estrogen and Cortisol.

Amine Hormones

Hormones with variable solubility; examples include Epinephrine (water-soluble) and Thyroxine (lipid-soluble).

Water-Soluble Hormones

Hormones that cannot cross the cell membrane and include peptide hormones and some amines.

Lipid-Soluble Hormones

Hormones that can diffuse across the cell membrane and include steroid hormones and some amines.

Receptor Location for Water-Soluble Hormones

Located on the cell surface.

Receptor Location for Lipid-Soluble Hormones

Located inside the cytoplasm or nucleus.

Mechanism of Action for Water-Soluble Hormones

Activates second messenger systems such as cAMP or Ca²⁺.

Mechanism of Action for Lipid-Soluble Hormones

Directly affects gene transcription.

Speed of Response for Water-Soluble Hormones

Fast response, typically within seconds to minutes.

Speed of Response for Lipid-Soluble Hormones

Slow response, typically within minutes to hours.

Duration of Effect for Water-Soluble Hormones

Short-lived effects.

Duration of Effect for Lipid-Soluble Hormones

Long-lasting effects.

Example of Water-Soluble Hormone Action

Insulin activates glucose uptake.

Example of Lipid-Soluble Hormone Action

Cortisol alters gene expression.