Hormones are chemical substances that act like messenger molecules that stream through the bloodstream. Hormones carry chemical messages from the glands where they are produced to cells in different parts of the human body. These chemical messages help to turn on or turn off cellular processes that control stress, appetite, growth , sleep cycles, blood sugar, sex drive, and sexual function.
The importance of hormones in the proper functioning of the human body is immense. They control the functions of organs and influence their growth, reproduction and sexual characteristics.
Moreover, hormones also affect the way a human body stores and uses energy and regulates the volume of fluids as well as the level of sugar and salt in the blood. Thus, a small amount of hormone can trigger a significant response in the human body.
What are Hormones?
Hormones are various chemicals released within the human body that regulate and control the activities of multiple organs. The introduction of hormones to the blood takes place via endocrine glands.
Our body contains two different kinds of glands.
- Endocrine Glands: These glands, such as the pituitary and adrenal glands, do not have ducts and deliver their secretions through the blood straight to the site of action.
- Exocrine Glands: These glands have ducts by which their secretions are transported. Example: sweat and liver,
What Is the Function of Hormones?
Hormones act as a messenger which is released into the blood. Blood transmits them to various organs and tissues of the human body. After reaching a target site, hormones bind to the receptors. Once this process is complete, hormones then transmit the message which causes an organ or tissue to perform a specific action.
The following are some important functions of hormones:
- Regulating mood and cognitive functions
- Growth and development
- Food metabolism
- Maintaining body temperature
- Controlling thirst and hunger
- Initiating and maintaining sexual development and reproduction
Hormones may be regulated by glands and organs, by a negative feedback mechanism, or by other hormones. Hormones that regulate the release of other hormones are defined as tropic hormones, which are secreted by the anterior pituitary in the brain.
Hormones During Pregnancy
Many hormone levels are affected in the body during pregnancy. Several hormones play major roles during pregnancy such as Estrogen, Progesterone, human chorionic gonadotropin hormone (hCG), and Human placental lactogen (hPL).
Chemical Nature of Hormones
Hormones may be chemically classified as either proteins or steroids. All of the hormones in the human body, except the sex hormones and those from the adrenal cortex, are proteins or protein derivatives.
What are The Properties of Hormones?
The significant properties of hormones are –
- They have a low molecular weight; thus, they can easily pass through capillaries.
- Hormones always act in low concentration.
- They are soluble in water so that they can be transported via blood.
- The importance of hormones is that they are non-antigenic. They are organic catalysts. Hormones act as coenzymes of other enzymes in the human body.
- Hormones, in their first action, cause a limited number of reactions and do not influence any metabolic activities of a cell directly.
- A significant characteristic of hormones is that, after their function is over, they are readily destroyed, excreted or inactivated.
- Hormonal activities are not hereditary.
Characteristics of Hormones
Hormones possess the following characteristics:
- Endocrine cells release hormones into the body.
- Circulating in bodily fluids, hormones are chemical messengers.
- They act on one portion of the body after being secreted in another.
- Unlike enzymes, hormones do not catalyse any reactions.
- They are not stored beforehand and are only secreted in minute amounts when necessary.
- The nervous system uses the feedback effect to control hormone secretion.
- The majority of the time, hormones have long-lasting impacts such as altered behaviour, growth, etc.
Classification of Hormones
The hormones produced in the human body are classified based on their chemical structure and nature as follows:
These hormones are made of polypeptide chains—linked chains of amino acids. The secretory vesicles serve as both a place for peptide hormone synthesis and storage. They are located in the membrane of the cell and are expelled from the parent cell through exocytosis. After being stored in vesicles, the substance is released when a stimulus causes a reaction, such as when high blood glucose levels cause the release of insulin. These hormones are water soluble but not fat soluble. The cell membrane comprises a phospholipid bilayer that prevents any fat-insoluble compounds from diffusing into the cell, preventing peptide hormones from passing through the membrane. Since the peptide hormones are unable to pass through the cell’s plasma membrane, the receptors are present on the target’s cell surface.
ADH (antidiuretic hormone), which is produced in the brain and released into the circulation by the posterior pituitary gland, is one example along with oxytocin and vasopressin.
These hormones are lipid-derived hormones that are obtained from cholesterol. On-demand, they are synthesised from precursors and released from the parent cell by a simple diffusion process. These hormones typically have the goal response of inducing the synthesis of new proteins because they bind to proteins while being transported through the blood. Steroid hormones, in contrast to peptide hormones, are fat-soluble and may pass through the cell membranes. Steroid hormones comprise sex hormones including progesterone, estrogen, and testosterone.
Functions of Hormones
The following are a few important functions that hormones perform:
- Metabolism of food.
- Development and growth.
- Controlling hunger and thirst.
- Preserving one’s body’s temperature.
- Maintain Homeostasis
- Regulating sleep and wake cycle
- Regulating mental and emotional functions.
- Establishing and sustaining sexual development and reproduction