Differences Between Endocrine and Paracrine Systems
The endocrine system communicates through hormones that are transported in the bloodstream to reach target cells, while the paracrine system involves local cell-to-cell communication where signals are sent to nearby cells. The endocrine system has a broader, systemic effect, whereas the paracrine system has a localized impact. Both systems are crucial for maintaining homeostasis in the body, but they differ in their mode of action and range of influence.
What Is The Endocrine System
The endocrine system is a complex network of glands and organs. It is responsible for controlling and regulating the body’s function using chemical messengers “hormones” including metabolites, lipids, steroids, peptides, and proteins [1, 2]. The hormones are secreted by the glands of the endocrine system, they travel through the bloodstream and control organs and tissues in the body. It is hormones that instruct the organs and tissues on what to do or how to function [1].
For instance, the endocrine system is responsible for cell-to-cell communication, important for maintaining metabolism, physiology and other aspects of organismal homeostasis. In addition, it helps with linking the brain to its organs and with enabling proper control of the metabolism, growth development and reproduction. Control of this system is through a complex feedback system that works in order to maintain homeostasis [3]. However, the endocrine system also plays a role in puberty, bone health and growth [4].
What Is The Paracrine System?
The paracrine system, also known as paracrine signalling, is crucial for biological processes including tissue development, repair and disease pathogenesis [5].
It ensures that the chemical messengers sent from the cell get into the extracellular environment. Such messengers, or also known as paracrine factors can be peptides, growth factors, hormones and other signalling molecules. They can be diffused over a short distance to nearby cells and bind to specific receptors to trigger a response [6].
These paracrine signals can initiate or suppress activity in populations of cells [7]. Paracrine signalling is context-dependent and can be turned on or off when hormonal outputs need to be adapted to changing demands of the organism, such as during reproduction, stress, inflammation, starvation, and circadian rhythms [6].
What Is The Difference Between Endocrine and Paracrine System?
Endocrine: Hormones travel through the bloodstream to act on distant target cells. Paracrine: Signaling molecules act on nearby cells in close proximity, without entering the bloodstream
Both endocrine and paracrine systems are methods of cellular communication in the body. The endocrine system is a network of glands and organs that secrete hormones directly into the bloodstream. For instance, the gastrointestinal hormones gastrin, cholecystokinin (CCK), secretin, glucose-dependent insulinotropic peptide (GIP), and motilin are classified as endocrines because they are secreted from enteroendocrine cells directly into the bloodstream before being delivered to target cells with receptor-specificity for the hormone [8].
Contrary to the endocrine system that secretes hormones into the bloodstream, the paracrine system involves the local action of hormones. Paracrine hormones or paracrine factors are secreted by cells and they reach their target destination by diffusion in the intracellular space. Therefore, they act locally and do not have to enter the systemic circulation in order to act [9, 8]. Examples of paracrine hormones include somatostatin and histamine, which are secreted by enteroendocrine cells and diffuse through the extracellular space to act locally on target tissues [8].
In summary, the primary difference between the endocrine and paracrine systems lies in the method of hormone delivery.