Cells of the body communicate either by chemical or hormonal "messengers." In the endocrine system, these messengers are hormones and may be amino acids/polypeptides or steroids. Endocrine hormones may travel long distances through the bloodstream. Chemical messengers can be leukotrienes, cytokines, prostaglandins, interleukins, and growth factors secreted by various cells for local communication and signaling.
The main purpose/goal of having various types of messengers is to allow for different cellular outcomes in an effector target organ. Each hormone or chemical ligand may bind to a cell surface receptor to generate a different or similar cellular response. Table 1 provides examples of these hormones.
Table 1. Water-soluble (Nonsteroidal) versus Fat-soluble (Steroidal) Hormones.Water-soluble / Amino Acid / Polypeptide Nonsteroidal Hormone Examples | Fat-soluble / Steroidal Hormone Examples |
Epinephrine and Norepinephrine
| Estrogen |
Antidiuretic Hormone/Vasopressin (ADH) | Testosterone |
Cortisol-Releasing Hormone (CRH)
| Progesterone |
Human Growth Factor | Cortisol |
Adrenocorticotropic Hormone (ACTH)
| Aldosterone |