Endocrine system
From Wikipedia, the free encyclopedia
The endocrine system is the system of glands, each of which secretes different types of hormones directly into the bloodstream (some of which are transported along nerve tracts[citation needed]) to regulate the body. The endocrine system is in contrast to theexocrine system, which secretes its chemicals using ducts. It derives from the Greek words "endo" meaning inside, within, and "crinis" for secrete. The endocrine system is an information signal system like the nervous system, yet its effects and mechanism are classifiably different. The endocrine system's effects are slow to initiate, and prolonged in their response, lasting from a few hours up to weeks. The nervous system sends information very quickly, and responses are generally short lived. Hormones are substances (chemical mediators) released from endocrine tissue into the bloodstream where they travel to target tissue and generate a response. Hormones regulate various human functions, including metabolism, growth and development, tissue function, and mood. The field of study dealing with the endocrine system and its disorders is endocrinology, a branch of internal medicine.
Features of endocrine glands are, in general, their ductless nature, their vascularity, and usually the presence of intracellular vacuoles or granules storing their hormones. In contrast, exocrine glands, such as salivary glands, sweat glands, and glands within thegastrointestinal tract, tend to be much less vascular and have ducts or a hollow lumen.
In addition to the specialised endocrine organs mentioned above, many other organs that are part of other body systems, such as thekidney, liver, heart and gonads, have secondary endocrine functions. For example the kidney secretes endocrine hormones such aserythropoietin and renin.
The endocrine system is made of a series of glands that produce chemicals called hormones. A number of glands that signal each other in sequence are usually referred to as an axis, for example, the hypothalamic-pituitary-adrenal axis.
Endocrine System parts and Function
Hypothalamus: A collection of specialized cells that are located in the lower central part of the brain is called the hypothalamus. The hypothalamus is the main link between the endocrine and the nervous systems. The nerve cells of the hypothalamus control the pituitary gland by stimulating or suppressing the hormone secretions.
Pituitary Gland: The pituitary gland is located at the base of the brain just below the hypothalamus. The pituitary gland is the most important part in the endocrine system. The pituitary gland secretes hormones on the basis of the emotional and seasonal changes. The hypothalamus sends information that is sensed by the brain to pituitary triggering production hormones. The pituitary gland is divided into two parts: the anterior lobe and the posterior lobe. The anterior lobe of the pituitary gland regulated the activity of the thyroid, adrenals, and the reproductive glands. The anterior lobe also produces hormones like:
Growth Hormone: To stimulate the growth of the bones and tissues. It also plays a role in the body's absorption of nutrients and minerals.
Prolactin: To activate the production of milk in lactating mothers
Thyrotropin: To stimulate the thyroid gland to produce thyroid hormones
Corticotropin: To stimulate the adrenal glands to produce certain hormones.
Endorphins are also secreted by the pituitary that acts on the nervous system and reduces the feeling of pain. The pituitary glands produces hormones that signal the reproductive organs to secrete sex hormones. The menstrual cycle and ovulation in women is also controlled by the pituitary gland. The posterior lobe of the pituitary gland produces antidiuretic hormone that helps to control the water balance in the body. Oxytoxins that trigger the contractions of the uterus in a woman who is in labor is secreted by the posterior lobe.
Thyroid Gland: The thyroid gland is situated in the front part of the lower neck that is shaped like a bow tie or butterfly. The production and secretions of the hormones of the thyroid glands are controlled by thyrotropin secreted by the pituitary gland. Thyroid produces thyroxine and triiodothyronine, that controls the rate at which the cells use up energy from food for production of energy. The thyroid hormones are very important as they help in growth of bones and the development and growth of the brain and nervous system in children. Over or under secretion of thyroid hormones leads to a number of thyroid problems in the body.
Parathyroids: These are four tiny glands that are attached to the thyroid gland. They release the parathyroid hormone that helps in regulating the level of calcium in blood along with another hormone produced by thyroid known as calcitinin.
Adrenal Glands: On each of the two kidneys, there are two triangular adrenal glands situated. The adrenal gland is divided into two parts. The outer part called the adrenal cortex produces corticosteroids, that influence and regulate the salt and water levels. They are also helpful in the body's response to stress, metabolism, immune system and the function and development of sexual organs. The inner part called the adrenal medulla, secretes catecholamines like epinephrine. This hormone is also called the adrenaline, it increases the blood pressure and heart rate when the body is under stress.
Pituitary Gland: The pituitary gland is located at the base of the brain just below the hypothalamus. The pituitary gland is the most important part in the endocrine system. The pituitary gland secretes hormones on the basis of the emotional and seasonal changes. The hypothalamus sends information that is sensed by the brain to pituitary triggering production hormones. The pituitary gland is divided into two parts: the anterior lobe and the posterior lobe. The anterior lobe of the pituitary gland regulated the activity of the thyroid, adrenals, and the reproductive glands. The anterior lobe also produces hormones like:
Growth Hormone: To stimulate the growth of the bones and tissues. It also plays a role in the body's absorption of nutrients and minerals.
Prolactin: To activate the production of milk in lactating mothers
Thyrotropin: To stimulate the thyroid gland to produce thyroid hormones
Corticotropin: To stimulate the adrenal glands to produce certain hormones.
Endorphins are also secreted by the pituitary that acts on the nervous system and reduces the feeling of pain. The pituitary glands produces hormones that signal the reproductive organs to secrete sex hormones. The menstrual cycle and ovulation in women is also controlled by the pituitary gland. The posterior lobe of the pituitary gland produces antidiuretic hormone that helps to control the water balance in the body. Oxytoxins that trigger the contractions of the uterus in a woman who is in labor is secreted by the posterior lobe.
Thyroid Gland: The thyroid gland is situated in the front part of the lower neck that is shaped like a bow tie or butterfly. The production and secretions of the hormones of the thyroid glands are controlled by thyrotropin secreted by the pituitary gland. Thyroid produces thyroxine and triiodothyronine, that controls the rate at which the cells use up energy from food for production of energy. The thyroid hormones are very important as they help in growth of bones and the development and growth of the brain and nervous system in children. Over or under secretion of thyroid hormones leads to a number of thyroid problems in the body.
Parathyroids: These are four tiny glands that are attached to the thyroid gland. They release the parathyroid hormone that helps in regulating the level of calcium in blood along with another hormone produced by thyroid known as calcitinin.
Adrenal Glands: On each of the two kidneys, there are two triangular adrenal glands situated. The adrenal gland is divided into two parts. The outer part called the adrenal cortex produces corticosteroids, that influence and regulate the salt and water levels. They are also helpful in the body's response to stress, metabolism, immune system and the function and development of sexual organs. The inner part called the adrenal medulla, secretes catecholamines like epinephrine. This hormone is also called the adrenaline, it increases the blood pressure and heart rate when the body is under stress.
Reproductive Glands or Gonads: The gonads are present in males and females and are the main organs producing sex hormones. In men, the gonads are related to testes. The testes are located in the scrotum and secrete androgens. The most important hormone for men testosterone is secreted from the testes. In women, ovaries are the gonads that are located in the pelvis region. They produce estrogen and progesterone hormones. Estrogen is involved during the sexual maturation of the girl, that is, puberty. Progesterone along with estrogen is involved in the regulation of menstruation cycle. These hormones are also involved during pregnancy.
Pancreas: These glands are associated with the digestive system of the human body. They secrete digestive enzymes and two important hormones insulin and glucagon. These hormones work together to maintain the level of glucose in the blood. If these hormones are not secreted in the required levels, it leads to development of diabetes.
Pineal: The pineal gland is located in the center of the brain. Melatonin is secreted by this gland that helps regulate the sleeping cycle of a person.
How Does Endocrine System Function with Other Systems?
The system that helps the body communicate, control and coordinate various functions is the endocrine system. The other systems with which this system interacts includes the nervous system, the reproductive system, liver, gut, pancreas, fat and the kidneys. This interaction is carried out via a network of glands and organs. These glands and organs can produce, store and secrete many types of hormones. Thus, this system helps control and regulate:
Reproductive system: Helps in controlling the formation of gametes
Skeletal system: Helps in controlling the growth of bones
Muscular system: Helps in controlling muscle metabolism
Excretory system: Helps control water in the kidneys
Respiration system: Helps in controlling the rate of respiration
The interaction with these systems helps in maintaining the energy levels within the body. It also affects the growth and development of the body as well as maintaining homeostasis. When one or more than one of the organs stop functioning or function abnormally, it leads to diseases and disorders. It leads to over or under production of hormones, that causes hormonal imbalance. The imbalance sends the normal functioning of other systems and organs to a toss, leading to diseases and disorders. For example, when the pancreas as affected it leads to diabetes.
Thus, the endocrine system regulates metabolism, growth, development, tissue functions, puberty and even moods. These are the basic functions that help keep our bodies in working condition. Any kind of problem will result in many disorders and abnormalities in the body. Thus, maintain a healthy diet so that the endocrine system can function under optimum conditions. Just as the car needs engine oil to run smoothly, our bodies require hormones to continue working efficiently.
Read more at Buzzle: http://www.buzzle.com/articles/endocrine-system-function.html
DISEASES
What is Addison's disease?
Addison's disease is an endocrine or hormonal disorder that occurs in all age groups and afflicts men and women equally. The disease is characterized by weight loss, muscle weakness,fatigue, low blood pressure, and sometimes darkening of the skin in both exposed and nonexposed parts of the body.
How does Addison's disease occur?
Addison's disease occurs when the adrenal glands do not produce enough of the hormone cortisol and, in some cases, the hormone aldosterone. The disease is also called adrenal insufficiency, or hypocortisolism.
What is cortisol?
Cortisol is normally produced by the adrenal glands, located just above the kidneys. It belongs to a class of hormones called glucocorticoids, which affect almost every organ and tissue in the body. Scientists think that cortisol has possibly hundreds of effects in the body. Cortisol's most important job is to help the body respond to stress. Among its other vital tasks, cortisol:
- helps maintain blood pressure and heart function
- helps slow the immune system's inflammation response
- helps balance the effects of insulin in breaking down sugar for energy
- helps regulate the metabolism of proteins, carbohydrates, and fats
- helps maintain proper arousal and sense of well-being
TREATMENT
Addison’s Disease Diagnosis
Exams and Tests to Figure Out If You Have Addison’s Disease
In trying to diagnose Addison’s disease (also known as primary adrenal insufficiency), your doctor (or endocrinologist, if you’ve gone to a doctor who specializes in the endocrine system) may run several exams and tests. This will help the doctor narrow down your condition to Addison’s disease; in the early stages, Addison’s symptoms may be confused with other disorders.
To begin the diagnostic process, your doctor will perform a physical examination that includes a thorough review of your medical and family history. Then he or she will probably move on to laboratory and imaging tests.
Baseline Laboratory Testing
The first step if your doctor suspects abnormal adrenal function may be to measure your cortisol and ACTH levels. ACTH is the acronym for adrenocorticotropin hormone. ACTH is necessary to tell the adrenal glands to produce cortisol and other hormones. Cortisol levels follow a natural cycle throughout the day; they are highest in the morning, so most likely your doctor will want to draw these labs around 8 am.
ACTH Stimulation Test: Used to Diagnose Primary Adrenal Insufficiency
To begin the ACTH stimulation test, your doctor will draw some blood and measure the cortisol level. At the same time, he or she will probably measure your ACTH level. Next, cosyntropin (a synthetic derivative of ACTH) is injected, and then the doctor will draw your blood again to re-evaluate your cortisol level. Usually, the doctor checks your level twice: 30 and 60 minutes after the injection.
TECHNOLOGY
What causes Addison's Disease?
Addison's disease may be caused by a disorder of the adrenal glands (primary adrenal insufficiency). The disease may also be caused if, for some reason, the pituitary gland stops producing enough adrenal stimulating hormone (secondary adrenal insufficiency).
In most cases primary adrenal insufficiency occurs as a result of the body's own immune system slowly destroying the outer layer of the adrenal glands. This form of Addison's is what is known as an autoimmune disease and accounts for about 70 per cent of cases. In developed countries tuberculosis (TB) accounts for about 20 per cent of cases of primary adrenal insufficiency because the adrenal glands are destroyed by the infection. When Dr Thomas Addison first identified the disease in 1849, TB was found to be the cause in 70 to 90 per cent of cases. Other less common causes of primary adrenal insufficiency are chronic infections, cancer cells spreading to the adrenal glands from other parts of the body, and surgical removal of the adrenal glands.
Secondary adrenal insufficiency is caused by a reduction in the amount of adrenal stimulating hormone (a substance called ACTH) produced by the pituitary gland. In most cases secondary adrenal insufficiency is caused by a pituitary tumour. It may also occur when high doses of steroids are used for long periods to treat other diseases such as asthma causing temporary or permanent loss of adrenal function.
Are any tests necessary?
An ACTH stimulation test is used to diagnose Addison's Disease. For this test levels of cortisol in the blood and/or urine are measured before and after an intravenous injection (into a vein) of a synthetic form of adrenal stimulating hormone. Cortisol levels are measured 30 to 60 minutes after the injection. Levels should rise during this time but, if there is adrenal insufficiency, there may be little or no rise in cortisol levels. If the results of this test are abnormal a longer test will be carried out. Your doctor will explain these tests to you.
Another test which may be used is an insulin-induced hypoglycaemia test. For this test blood glucose and cortisol levels are measured, and an injection of a fast-acting insulin is then given. The levels are measured again at 30, 45 and 90 minutes following the injection. The normal response is for blood glucose levels to fall and cortisol levels to rise.
Secondary adrenal insufficiency may be caused by a pituitary problem so a CT scan of the pituitary gland may be ordered.
What treatment is available?
Treatment of Addison's disease involves therapy to replace the hormones that are not being produced by the adrenal glands. Cortisol is replaced with tablets containing a synthetic steroid called hydrocortisone. If there is also a deficiency of aldosterone, tablets containing another steroid such as fludrocortisone acetate (Florinef®) can be given.
People with Addison's disease should always carry some identification stating their medical condition so that cortisol injection can be given in an emergency. Some people wear a bracelet or neck chain containing relevant information. When travelling, it is advisable for sufferers to carry an emergency syringe and an injectable form of cortisol.
Medication for Addison's disease should be increased during periods of stress or mild respiratory infections to prevent complications of the disease. If severe infections occur, or if diarrhoea and vomiting occur meaning that the oral tablets are not being absorbed properly, medical attention must be sought promptly.
