Hormones are chemicals that carry messages from glands to cells within tissues or organs in the body. They also maintain chemical levels in the bloodstream to help achieve homeostasis, which is a state of stability or balance within the body. There are two types of these chemicals, known as steroids and peptides. The word "hormone" comes from a Greek word that means "to spur on." This reflects how hormones act as catalysts for chemical changes at the cellular level that are necessary for growth, development and energy.
As members of the endocrine system, glands manufacture hormones. These chemicals circulate freely in the bloodstream, waiting to be recognized by a target cell, which is their intended destination. The target cell has a receptor that can be activated only by a specific type of hormone, after which the cell knows to start a certain function within its walls. Genes might get activated, for example, or energy production resumed. An autocrine hormone acts on the cells of the secreting gland, and a paracrine hormone acts on nearby — but unrelated — cells.
In general, steroids are sex hormones that are related to sexual maturation and fertility. Steroids are made from cholesterol, either by the placenta when the body is still inside the mother's womb or by the body's adrenal gland or gonads — the testes or ovaries — after birth.
Cortisol, an example of a steroid hormone, breaks down damaged tissue so that it can be replaced. Steroids determine physical development and fertility cycles from puberty through old age. If a person's body is not synthesizing the correct steroidal hormones, he or she can sometimes supplement them pharmaceutically, as with estrogen and progesterone.
Peptides regulate other functions, such as sleep and blood sugar concentration. They are made from long strings of amino acids, so they sometimes they are referred to as protein hormones. Human growth hormone, for example, helps the body burn fat and build muscles. Another peptide hormone, insulin, starts the process to convert sugar into cellular energy.
Hormones so perfectly and efficiently manage homeostasis because of negative feedback cycles. The body's goal is to keep the concentration of a certain chemical, such as testosterone, at a constant level for a certain period of time, similar to how a thermostat works. Using negative feedback, a change in conditions causes a response that returns the conditions to their original state. For example, when a room's temperature drops, the thermostat responds by turning on the heat. The room then returns to the ideal temperature, and the heater turns off, keeping the conditions relatively constant.
Hormones control the functioning of the body in various ways. A hormone stimulates or inhibits the release of another hormone and controls the functions of the bodily systems like the immune system, digestive system, reproductive system, nervous system, etc. Hormones determine the rate of metabolism and the overall health and behavior pattern of an individual. The following table describes the significance of hormones and their functions. Take a look at the list of hormones to understand the wonderful mechanism of human body.
|
Name and Description |
Origin |
Main Functions |
|
Adiponectin (Acrp30) |
Adipose tissue or body fat |
It controls several metabolic processes like glucose regulation and lipid catabolism, helps prevent diseases like atherosclerosis, obesity, type 2 diabetes, non-alcoholic fatty liver disease (NAFLD), etc. |
|
Adrenocorticotropic hormone
(ACTH) |
Anterior pituitary |
It enhances lipoprotein uptake into cortical cells so that more cholesterol is made available to the cells of the adrenal cortex. It promotes the transport of cholesterol into the mitochondria and stimulates its hydrolysis. It plays an important role in the synthesis and secretion of gluco- and mineralo-corticosteroids and androgenic steroids. |
|
Aldosterone |
Outer part of the adrenal cortex in the adrenal gland |
It promotes reabsorption of sodium in kidneys and increased blood volume, release of potassium and hydrogen through kidneys, increased water retention and rise in blood pressure levels. |
|
Androstenedione |
Adrenal glands and the gonads |
It promotes the production of estrogen in granulosa cells by supplying androstenedione substrate. |
|
Angiotensinogen and
angiotensin |
Liver |
It secretes aldosterone from adrenal cortex dipsogen, and causes vasoconstriction or the narrowing of the blood vessels. |
|
Antidiuretic hormone
(ADH) |
Posterior pituitary |
It secretes ACTH in anterior pituitary, causes vasoconstriction up to a moderate degree, and causes water retention in kidneys. |
|
Antimullerian hormone (AMH) |
Testes |
It curbs the secretion of prolactin and TRH from anterior pituitary, and inhibits the development of the mullerian ducts into the uterus. |
|
Atrial-natriuretic peptide (ANP)(Atriopeptin) |
Heart |
It enhances the glomerular filtration rate (GFR), leading to greater excretion of sodium and water, and enhances the release of free fatty acids from adipose tissue. |
|
Brain natriuretic peptide
(BNP) |
Heart |
It helps to lower blood pressure as it helps reduce systemic vascular resistance. It also lowers the level of blood water, sodium and fats. |
|
Calcidiol |
Skin/proximal tubule of kidneys |
It is useful to know the vitamin D status, and promotes absorption of calcium from the gut. |
|
Calcitonin (CT) |
Thyroid gland |
It lowers blood calcium levels by inhibiting calcium absorption in the intestines, and it also inhibits absorption of calcium by kidneys and thus promotes excretion of calcium through urine. It prevents osteoclast activity in bones and plays an important role in vitamin D regulation. |
|
Calcitriol |
Skin/proximal tubule of kidneys |
It controls the transfer of calcium from blood to the urine by kidneys, enhances absorption of calcium from the gut into the blood and promotes the release of calcium into the blood from bone. It also inhibits the release of calcitonin. |
|
Cholecystokinin (CCK) |
Duodenum (first part of the small intestine) |
It promotes the release of digestive enzymes from the pancreas and bile from the gallbladder, plays the role of a hunger suppressant, it is associated with drug tolerance and is involved in exhibition of symptoms of drug withdrawal. It is responsible for proper digestion and satiety. |
|
Corticotropin-releasing hormone
(CRH) |
Hypothalamus |
It is released in response to stress, promotes the release of ACTH from anterior pituitary, determines the gestation period and triggers the onset of parturition and the timing of delivery. |
|
Cortisol (a steroid
hormone) |
Adrenal cortex |
It is produced in response to stress and decreased level of blood glucocorticoids. It regulates the metabolism of glucose, and suppresses the immune system. It promotes the metabolism of fat, protein and carbohydrate, it reduces bone formation. It also promotes maturation of the lungs of the fetus. It controls sodium loss through the small intestine and helps maintain the pH. It is a diuretic hormone which helps enhance gastric acid secretion and release of copper enzymes. |
|
Dehydroepiandrosterone
(DHEA) |
Testes, ovaries, kidneys |
It plays an important role in virilization (prenatal changes that determine the sex, postnatal changes leading to normal male puberty, and effects of too much androgen in girls or women) and anabolism (involves processes that lead to development of organs and tissues). |
|
Dihydrotestosterone (DHT) |
The enzyme 5α-reductase promotes the production of the hormone in the prostate, testes, hair follicles, and adrenal glands. |
It's responsible for male pattern baldness. It plays an important role in prostate growth (benign prostatic hyperplasia and prostate cancer) and differentiation. |
|
Dopamine (DPM/PIH/DA) |
Kidneys and hypothalamus. |
It determines your behavior, cognition and voluntary movement. It increases heart rate and blood pressure. It plays an important role in the psychological features like motivation, punishment and reward. It controls the sleep pattern, mood, concentration, working memory, and learning skills. |
|
Endothelin |
X cells of the stomach |
It promotes smooth contraction of the stomach muscles. |
|
Enkephalin |
Kidneys |
It is associated with the regulation of pain. |
|
Epinephrine (EPI) |
Adrenal medulla |
It determines the 'flight or fight' response, enhances the supply of oxygen and glucose to the brain and muscles by increasing the heart rate and stroke volume, and enhances the catalysis of glycogen in liver, etc. It promotes relaxation/contraction of smooth muscles depending upon the tissue it acts upon. It also stimulates the breakdown of lipids in fat cells. It suppresses the activities of the immune system. |
|
Erythropoietin
(EPO) |
Kidneys |
It enhances the production of erythrocytes (red blood cells). |
|
Estradiol (E2) |
In males: Testes; In females: Ovaries |
In males, it prevents apoptosis (programed cell death) of germ cells. In females, it plays an important role in blood coagulation, fluid balance, certain types of breast cancers, functioning of the lungs, health of blood vessels and skin, etc. It enhances fat burning activity, uterine and endometrial growth, bone formation, etc. It determines your height, helps lower muscle mass, and reduces bowel movement. It promotes protein synthesis and increases good cholesterol, triglyceride, cortisol, growth hormone, etc. |
|
Estriol (E3) |
Placenta during pregnancy |
It helps keep the uterus quiescent during pregnancy. |
|
Estrone (E1) |
Ovary and adipose tissue |
It helps maintain the overall health, especially the health of postmenopausal women and keeps certain diseases away. |
|
Follicle-stimulating hormone (FSH) |
Anterior pituitary gland |
Follicle-stimulating hormone function involves maturation of Graafian follicles in the ovaries. It promotes spermatogenesis and stimulates the production of androgen-binding protein in testes, in men. It governs the growth, onset of puberty and other reproductive processes of the body. |
|
Gastrin (GRP) |
Stomach, duodenum and pancreas |
It stimulates the production of certain digestive enzymes like pepsin, promotes stomach contractions, enhances antral muscle mobility and secretion of gastric acid, triggers pancreatic secretions and emptying of gallbladder, etc. |
|
Ghrelin |
Stomach, pancreas |
It stimulates your appetite and also regulates the release of growth hormone from the anterior pituitary gland. |
|
Glucagon (GCG) |
Pancreas |
It raises blood glucose levels. It is released when blood glucose levels drop. It stimulates the process of conversion of stored glycogen into glucose in the liver. |
|
Gonadotropin-releasing hormone
(GnRH) |
Hypothalamus |
It triggers the release of FSH and LH (luteinizing hormone) from the anterior pituitary gland. |
|
Growth hormone (GH or hGH) |
Anterior Pituitary |
It triggers cell reproduction and determines the growth and regeneration. It strengthens the bones by increasing calcium retention, helps maintain the function of pancreatic islets, it enhances protein synthesis, increases muscle mass and strengthens the immune system. It is responsible for the growth of the internal organs except brain. It also promotes the breakdown of lipids and hydrolysis of triglycerides. |
|
Growth hormone-releasing hormone
(GHRH) |
Hypothalamus |
It triggers the release of growth hormone from the anterior pituitary gland. |
|
Histamine |
Stomach |
It stimulates the release of gastric acid. It also triggers the inflammatory responses of the body. It plays an important role in sleep regulation and marital function, memory, and immune system disorders and allergies. |
|
Human Chorionic Gonadotropin
(hCG) |
Placenta |
It helps maintain the health of the corpus luteum during early pregnancy, leading to increased release of progesterone. Thus, it helps protect the fetus. It determines the severity of morning sickness in pregnant women. |
|
Human placental lactogen
(HPL) |
Placenta |
It carries anti-insulin properties. It raises maternal blood glucose levels and decreases maternal glucose utilization. It thus ensures adequate nutrition for the fetus. It increases insulin resistance and carbohydrate intolerance. |
|
Inhibin |
Fetus, testes and ovaries |
It inhibits FSH production and secretion. |
|
Insulin |
Beta cells of the pancreas |
It governs the metabolism of carbohydrates and fats, helps maintain blood glucose levels by promoting the absorption of glucose in the cells of liver, muscle, and fat tissues. Glucose is stored in the form of glycogen in the muscles and the liver. Insulin inhibits the release of glucagon and does not allow the body to use fat as an energy source. It is involved in several metabolic processes. |
|
Insulin-like growth factor (IGF or somatomedin) |
Liver |
It governs the growth and development of cells. Both insulin and IGF play an important role in aging. Studies show that IGF-1 is sometimes responsible for the development of both prostate and breast cancer cells. |
|
Leptin (LEP) |
Adipose tissue |
It decreases your appetite and increases the rate of metabolism. Leptin and ghrelin play an important role in weight management. |
|
Leukotriene (LT) |
Eicosanoid lipid mediators |
It stimulates contractions in the smooth muscles located in the lining of the trachea and is mainly involved in the inflammatory response of the body. |
|
Lipotropin (PRH) |
Anterior pituitary |
It promotes the breakdown of lipids and triglycerides. It also stimulates the processes that lead to the production of steroids from cholesterol and transformation of a steroid to another steroid. It also encourages melanocytes to produce melanin. |
|
Luteinizing hormone
(LH) |
Anterior pituitary |
It regulates ovulation in females. In males, testosterone is produced in the testicles in the presence of this hormone. |
|
Melanocyte stimulating hormone
(MSH or α-MSH) |
Internediate lobe of the pituitary |
It controls your appetite and helps in procreation functioning. It stimulates the melanocytes in skin and hair to produce and release more melanin. |
|
Melatonin
(MT) |
Pineal gland |
It works as an antioxidant and plays an important role in the circadian rhythms. It is released in darkness and causes drowsiness. |
|
Neuropeptide Y (NPY) |
Hypothalamus |
It promotes several physiologic processes in the brain, like, regulation of memory, cognition, etc. It may lead to increased food intake and decreased physical activity. |
|
Norepinephrine
(NRE) |
Adrenal medulla |
It determines the fight or flight response. Epinephrine and nonepinephrine are stress hormones and they increase heart and respiration rates. |
|
Orexin |
Hypothalamus |
It is responsible for increased appetite, high energy level and stamina. It also controls wakefulness. |
|
Oxytocin (OXT) |
Posterior pituitary |
It is essential for the release of breast milk. It also governs the contraction of muscles. It regulates body temperature, determines the activity level and governs wakefulness. |
|
Pancreatic polypeptide |
Pancreas |
It helps the pancreas in the secretion activities, regulates glycogen levels in the liver and gastrointestinal secretions. |
|
Parathyroid hormone
(PTH) |
Parathyroid gland |
It plays an important role in maintaining blood calcium levels and promotes calcium reabsorption in kidneys. It lowers blood phosphate and activates vitamin D. |
|
Progesterone (P4) |
Ovaries and adrenal glands; and placenta during pregnancy |
It regulates the menstrual cycle and supports pregnancy. It also promotes thyroid function and bone growth. It is involved in relaxation of smooth muscles, use of fat stores for energy, it helps maintain zinc and copper levels and oxygen level in cells, it helps prevent endometrial cancer. It is associated with several other important processes that take place in the body. |
|
Prolactin (PRL) |
Anterior pituitary and uterus |
It stimulates the production of milk in mammary glands and is responsible for feelings of pleasure. |
|
Prolactin Releasing Hormone (PRH) |
Hypothalamus |
It stimulates the release of prolactin in the anterior pituitary gland. |
|
Prostacyclin (PGI2) |
Endothelium (cells in the thin layer which covers the interior surface of blood vessels) |
It is involved in the relaxation of smooth muscles and widening of blood vessels. |
|
Prostaglandins (PG) |
Seminal vesicle |
They perform different functions in different areas. They control calcium movement, promote cell growth, flow of the hormones, trigger hypothalamus to produce fever, promote constriction or dilation in vascular smooth muscle cells, lower intraocular pressure, induce labor, give us the feeling of pain, help to enhance the rate of glomeruli filtration, etc. |
|
Relaxin (RLN) |
Uterus |
Its exact function is not yet known. It is believed that it increases the motility of sperms in semen. In women, its levels keep on changing during the menstruation cycles. |
|
Renin |
Kidneys |
It influences the mean arterial blood pressure in the body. It raises blood pressure and helps maintain the perfusion pressure in the kidneys. |
|
Secretin (SCT) |
Duodenum |
It regulates the secretions into the duodenum. It inhibits the production of gastric juice and helps maintain the pH of the duodenum. It controls the osmotic pressure in the body. Latest researches have shown that it is responsible for maintaining normal osmotic pressure in the hypothalamus, pituitary gland, and kidneys. |
|
Serotonin
(5-HT) |
Central nervous system, gastrointestinal tract |
It regulates movements of the intestine, appetite, sleep and mood. It determines your learning skills and memory. It also plays an important role in 'blood clotting' and 'wound healing'. |
|
Somatostatin (SRIF) |
Hypothalamus, gastrointestinal tract, islets of Langerhans (pancreas) |
It brings down the rate of smooth muscle contractions and lowers the blood flow within the intestine and thus lowers the rate of gastric emptying. It curbs the action of pancreas and inhibits the release of insulin and glucagon. It curbs the release of gastrointestinal hormones and growth hormone (GH). |
|
Testosterone (Male sex
hormone) |
Testes in males and ovaries in females, adrenal glands. |
It determines the bone density, strength and muscle mass. It plays an important role in the growth of the Adam's apple, beard and axillary hair, chest hair, leg hair, etc., and in the associated changes like deepening of voice, puberty (maturation of sexual organs), development of scrotum, etc. |
|
Thrombopoietin
(TPO) |
Liver, kidneys, striated muscles. |
It helps produce platelets in the bone marrow. |
|
Thromboxane (TXA2) |
Platelets |
It plays an important role in clotting of blood (thrombosis). It promotes aggregation of platelets and acts as a vasoconstrictor. |
|
Thyroid-stimulating hormone
(TSH) |
Anterior pituitary gland |
It regulates the release of thyroxine (T4) and triiodothyronine (T3). |
|
Thyrotropin-releasing hormone
(TRH) |
Hypothalamus |
It regulates the release of thyroid-stimulating hormone, and it promotes the release of prolactin in the anterior pituitary gland. |
|
Thyroxine (T4) |
Thyroid gland |
It regulates the rate of metabolic processes, it plays an important role in protein synthesis and determines the physical growth. |
|
Triiodothyronine (T3) |
Thyroid gland |
It stimulates the basal metabolic rate, it increases the heart rate, the rate of protein synthesis and protein degradation, glucose synthesis, lipolysis, etc. It plays an important role in the development of embryo and infants. |