Hormones: Types, Function, and Classification

• A hormone is a chemical transmitter that is released in small amounts from glands.
• Hormones are transported in the bloodstream to target organs or other cells.
• Hormones are chemical messengers.
• Hormones transfer information from one set of cells to another.
• Hormones regulate growth, development, mood, tissue function, metabolism, and sexual function.
• Hypo or hypersecretion of any hormone can be harmful to the body.
• Controlling hormone production can treat many hormonal disorders.

Hormone Classification

• Hormones are classified by chemical nature.
• There are two main groups of hormones: amino acid-based and steroids.
• Amino acid-based hormones include proteins, peptides, and amines.
• Peptides are chains of amino acids and are smaller than proteins.
• Amines are a derivative of ammonia.
• Steroids are made from cholesterol and are lipid-based.
• Prostaglandins are local hormones made from highly active lipids released from almost all cell membranes.

Hormone Specificity

• Hormones are specific.
• Hormones target a specific cell or organ.
• Target cells must have specific protein receptors.
• Hormone binding alters cellular activity.
• Hormone binding to its target cell is similar to an enzyme and its substrate, like a lock and key mechanism.

Steroid Hormone Action

• Steroid hormones diffuse directly through the cell membrane.
• Steroid hormones enter the nucleus.
• Steroid hormones bind to a receptor protein within the nucleus.
• The hormone-receptor complex binds to specific sites on the cell's DNA.
• Certain genes are activated to synthesize new proteins.

Second-Messenger System (non-steroids)

• A hormone (first messenger) binds to a membrane receptor.
• The activated receptor sets off a series of reactions that activates an enzyme.
• The enzyme catalyzes a reaction to produce a second messenger.
• The second messenger manages additional intracellular changes to promote a specific response in the target cell.

Explore hormones, the body's chemical messengers that regulate growth, metabolism, and sexual function. Learn about amino-acid based hormones like peptides and amines, and steroid hormones derived from cholesterol. Understand the role of hormones in transferring information between cells.