Hormones (mechanisms of action)

A. Peptide Hormones: Secondary Messengers

- ex: ADH, Insulin

- polar (H2O soluble, fat insoluble)

- outside cell messenger

- bind to receptors on cell SURFACE, trigger cAMP cascade (inactivated by phosphodiesterase)

B. Steroid Hormones: Primary Messengers

- ex: Estrogen, Aldosterone

- classic ring structure, all derived from CHOLETEROL

- non-polar, lipid-soluble so can directly pass from cell's phospholipid membrane

- inside the cell messengers, goes into nucleus, targets gene expression

C. Amino Acid Derivative Hormones

ex: Epinephrine

- can act as EITHER peptide hormones OR steroid hormones!