Classification of hormones

Classification of hormones

Signaling pathways

• Paracrine hormones: affect the neighboring cells through diffusion
• Autocrine hormones: affect the secreting cell itself
• Endocrine hormones: are secreted into the bloodstream to reach their targets
  

Chemical nature

• Steroid hormones: derived from cholesterol
• Amine hormones: derived from a single amino acid such as phenylalanine, tyrosine, or tryptophan

Biochemical properties

• Lipophilic hormones: steroid hormones and thyroid hormones
• ‍Hydrophilic hormones: peptide/protein hormones and amine hormones (except for thyroid hormones)

Lipophilic hormones (e.g., adrenocortical steroid hormones) pass into the bloodstream once synthesized. They are not stored by cells.

Hydrophilic hormones (e.g., catecholamines) are stored in secretory granules and are released when needed.