The endocrine system consists of many organs and glands located throughout the body. These glands produce hormones that regulate most of the body's systems, including metabolism, emotions, fertility, and heart rate.
This article describes the anatomy and function of the endocrine system. It also includes information on how common endocrine disorders are diagnosed and treated.
Your endocrine system has three main parts:
- Glands: small organs that produce and secrete hormones.
- Hormones: chemical messengers that travel through the bloodstream to transmit messages to tissues or organs.
- Cellular receptors: they target cells that receive hormonal signals.
When the hypothalamus receives a signal from the nervous system, it releases hormones that tell the pituitary gland what hormones to produce and / or secrete.
The pituitary gland releases hormones into the bloodstream that travel to its target cells to activate or suppress them.
The endocrine system maintains the stability of the body's systems. The hypothalamus closely monitors when hormonal activity is too high or too low, and it responds by informing the pituitary gland to increase or decrease the production and release of hormones.
Receptors and hormones are very specific. Only one type of hormone matches its specific receptors on the cell.
Endocrine glands and hormones.
The body has eight main endocrine glands and many small ones. By contacting the pituitary hormone, the endocrine glands produce their own hormones that perform certain functions. The main endocrine glands are the following:
The pituitary gland consists of two lobes: anterior and posterior. The anterior lobe receives signals from the hypothalamus to produce hormones. The posterior lobe does not produce its own hormones, it secretes two hormones produced by the hypothalamus.
The anterior lobe emits:
- Prolactin : a hormone that stimulates breast growth and milk production during and after pregnancy.
- Somatropin : growth hormone that stimulates the growth of bones and tissues throughout the body.
- Follicle Stimulating Hormone (FSH): stimulates sperm production in men and helps regulate the menstrual cycle and egg growth in women.
- Luteinizing hormone (LH): hormone that stimulates the production of sex hormones: estrogen and progesterone in women and testosterone in men.
- Thyrotropin: a hormone that stimulates the production of hormones by the thyroid gland , which are responsible for processes such as your body's development and metabolism.
- Adrenocorticotropin Hormone: A hormone that stimulates the adrenal glands to produce cortisol, which helps regulate metabolism, the immune system, the response to stress, and more.
The posterior lobe emits:
- Antidiuretic Hormone (ADH): A hormone that tells the kidneys how much water to filter from the blood and urine.
- Oxytocin – Hormone responsible for social bonding, sexual pleasure, breast milk production, and more.
The thymus is used mainly during childhood, since its function is to produce hormones that help develop the immune system.
Around puberty, its tissues are replaced with fat, after which the thymus is no longer necessary for normal immune function.
Hormones secreted by the thymus gland include:
- Thymosin: a hormone that stimulates the production of T lymphocytes, white blood cells that help your body fight viruses, bacteria, and cancer.
- Thymopoietin: a youth hormone that affects the rate of skin aging and prevents skin and brain cells from aging too quickly.
- Thymulin – Another essential hormone for youth development and T cell function.
Located in the brain, the pineal gland is a small gland that secretes melatonin , a hormone that regulates the sleep-wake cycle. Melatonin is also important for your immune system and helps reduce inflammation in your body.
The thyroid gland is a gland located in the windpipe at the front of the throat. It uses iodine from food to produce three hormones:
- Thyroxine (T4): hormone that influences metabolism, mood, and body temperature.
- Triiodothyronine (T3): hormone that helps regulate metabolism.
- Calcitonin: hormone that helps regulate calcium levels.
The thyroid gland also contains four tiny parathyroid glands. They produce parathyroid hormone, which controls the levels of calcium and phosphorus in the body.
There are two adrenal glands, one on top of each kidney. Each adrenal gland is divided into two regions, the cortex and the medulla, which have very different functions.
Hormones produced by the adrenal cortex include:
- Glucocorticoids – A group of hormones that fight inflammation in the body and are essential for metabolism, circulation, mood, and the sleep-wake cycle.
- Mineralocorticoids: A group of hormones that maintain the balance of water, salt, and potassium in the bloodstream.
- Androgens and estrogens: Some androgens and a small amount of estrogens are produced in the adrenal cortex.
Hormones produced by the adrenal medulla include:
- Adrenaline : Also known as adrenaline, a hormone that is released when the fight or flight response is activated.
- Norepinephrine : Along with adrenaline, norepinephrine increases heart rate and blood pressure, and increases blood sugar (glucose) levels during the fight or flight response.
The pancreas is a large gland in the abdomen that secretes two hormones, which are necessary to maintain normal blood sugar (glucose) levels:
- Glucagon: a hormone that stimulates the liver to release more glucose in the body.
- Insulin: a hormone that helps cells metabolize glucose and convert it into energy.
In women, these two small glands produce three hormones necessary for sex and reproduction:
- Estrogen – A female sex hormone that regulates the menstrual cycle, promotes breast and pubic hair growth, helps maintain bone strength, and more.
- Progesterone: a hormone that helps regulate the menstrual cycle and prepares the uterus for pregnancy when an egg is fertilized by sperm.
- Inhibin : a hormone that controls the level of follicle-stimulating hormone that regulates egg development.
A pair of glands found only in men, the testes secrete testosterone, a hormone that regulates male sexual desire and sperm production. It is also responsible for the development and maintenance of male sexual characteristics, such as facial hair and deep voices, as well as denser muscle and bone mass.
Types of endocrine diseases.
Any time one of these hormones gets out of balance, it can affect many other systems, glands, and hormones.
Endocrine-related disorders include:
- Polycystic Ovarian Syndrome – A condition that occurs when altered levels of FSH, LH, androgens, or insulin affect a woman's estrogen levels. The result can include changes in weight, metabolism, and energy.
- Diabetes – A condition in which the pancreas does not produce enough insulin, resulting in high blood sugar levels. Symptoms include frequent urination, fatigue, blurred vision, and severe hunger.
- Osteoporosis – Low estrogen levels, often due to menopause, lead to bone loss and brittle bones. Osteoporosis can also be caused by calcium deficiency or high levels of parathyroid hormone.
- Addison's disease : a condition in which the adrenal glands do not make enough cortisol or aldosterone. Symptoms include abdominal pain, menstrual irregularities, depression, and salt cravings.
- Hypothyroidism : a condition in which the thyroid gland does not make enough thyroid hormones. Symptoms include fatigue, increased sensitivity to cold, dry skin, and weight gain.
- Hyperthyroidism – A condition in which the thyroid gland produces too many hormones, resulting in weight loss, hand tremors, irregular heartbeats, increased appetite, itchy skin, and more.
- Cushing syndrome : also known as Hypercortisolism, Cushing's syndrome, occurs when the adrenal glands make too much cortisol. This leads to symptoms like fatigue, depression, muscle weakness, and fertility problems.
Endocrine disorders develop for various reasons. Trauma, infection, genetic disorder, disease, or tumor can cause the disorder. Endocrine disease can begin immediately or years after damage to the gland.
If your healthcare provider suspects that your symptoms may be related to your endocrine system, they will most likely have blood tests to check for hormonal imbalances. You may be asked to give a urine or saliva sample.
Depending on the results, you may be referred to an endocrinologist , a doctor who specializes in conditions related to the endocrine system.
Endocrinologists perform more detailed tests to determine the cause of your hormonal imbalance. This often includes so-called stimulation and suppression tests.
For these tests, you will be injected with hormones that start (stimulate) or suppress (slow down) the production of certain hormones. The endocrinologist will then evaluate your body's response.
For example, to test for Cushing's syndrome, your doctor will prescribe a steroid called dexamethasone, which blocks cortisol production. Then a blood test that measures the level of cortisol in the body can help determine if the adrenal glands are making too much cortisol.
In some cases, a malignant or non-malignant growth in the gland can cause the gland to produce too many hormones. To confirm or rule out a tumor, doctors may order a CT scan or MRI to examine the gland in more detail.
Most endocrine diseases cannot be cured and, if left untreated, some can be life threatening. However, with early diagnosis and treatment of endocrine disorders, hormonal imbalances and symptoms can be controlled.
The first line of treatment is usually hormone therapy. It can be a hormone replacement when you are taking a hormone that you lack. Or, if your body is making too much hormone, you may be prescribed hormone suppression therapy to slow down hormone production.
Hormone therapy is usually taken as a pill and sometimes as an injection or patch that is applied to the skin. An example is the estradiol skin patch, which delivers estrogen to relieve menopausal symptoms and can prevent osteoporosis.
If a tumor is causing a hormonal imbalance, chemotherapy may be given to kill cancer cells and prevent them from spreading. Surgical removal of all or part of the tumor may also be necessary.
The endocrine system is a complex network of glands, hormones, and receptors that control most of the body's processes. It is inspired by the hypothalamus, a tiny organ in your brain that has one great purpose: to keep these processes stable in the body with the correct dose of hormones.
Endocrine disorders can develop for many reasons beyond your control. If your doctor is concerned that you may have a hormonal imbalance, he or she will monitor your hormone levels and possibly prescribe medication to stabilize them.
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Fatigue, weight change, and depression are common symptoms of many endocrine diseases. If you have these problems, you may be inclined to blame your symptoms on a busy schedule or stress.
However, you should never feel like your body is out of control. See your doctor to find out the cause of your symptoms. The right treatment plan can restore balance to your body and help you feel like yourself again.