Many of our body functions including metabolism, growth and development, metabolism, electrolyte balances and reproduction are regulated by the human endocrine system. There are several hormones producing glands in our body that produce hormones.The hypothalamus produces several releasing and inhibiting factors which control release or inhibition of hormones by other glands.
Some of the famous hormone producing gland throughout the body include adrenal gland which produces cortisol primarily, gonads which produce sex hormones, pancreas which produces insulin and glucagon and the thyroid which produces thyroid hormones1. All of them are included in a large category of organs grouped into the endocrine system.
Hormones can be considered as the means through which cells communicate with each other. So, one can define hormone as the inter-cellular messenger. This definition is much more inclusive than the original one according to which hormones are the substances produced by glands which travel through blood circulation to act on the target cells23.
Life exists in a complex state of equilibrium known as “homeostasis” which is constantly challenged by intrinsic or extrinsic factors. Hormones produced by the endocrine systhem have a crucial role in fighting against these extrinsic or intrinsic factors and in maintaining the equilibrium4.
Hormones have another very crucial role. There are some energy rich substrates ( glucose, free fatty acids and amino acids ) and auxiliary elements such as calcium/phosphorus in the body. Hormones store these substrates with the help of energy storage hormones including insulin, androgen and osteocalcin etc.
During the attack of systemic infectious diseases, energy expenditure hormones which include cortisol ( breakdown of liver glycogen/muscle protein, gluconeogenesis; water retention ), adrenaline, growth hormone, angiotensin 2 and thyroid gland hormones release these substrates and help the energy-consuming immune system to cope with the infection5.
Functions of hormones produced by the human endocrine system can be broadly grouped into several categories:
1. Reproduction and sexual differentiation
2. Development and Growth
3. Maintenance of the internal environment
4. Regulation of metabolism
5. Nutrition supply
A single hormone may affect more than one of these functions and each function may be controlled by several hormones8.
Cells of the atrium of heart produce atrial natriuretic factor (ANF) and brain natriuretic peptide (BNP). These two substances modulate the system that tends to increase the extracellular fluid volume and blood pressure9.
8. H.all J, Guyton A. Guyton And Hall Review Of Physiology. Edinburgh: Elsevier Saunders; 2005:905-915
9. Ganong W. Review Of Medical Physiology. New York: Lange Medical Books; 2005:301-307,377-390.