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The Endocrine System
The endocrine system is a group of glands that regulate the body with hormones. The glands are ductless, so they release hormones directly into the bloodstream. Hormones are chemical messengers that have specific targets called receptors. There are three types of hormones: steroid hormones, amino acid derivatives, and peptide hormones. The concentration of hormones in the bloodstream is regulated through feedback loops.
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Glands and Hormones
This list of endocrine system facts includes the glands and the hormones they produce:
- Hypothalamus - The hypothalamus is located at the base of the middle portion of the brain. Several hormones are produced by the hypothalamus, including thyrotropin-releasing hormone, dopamine and oxytocin.
- Pituitary - The pituitary gland is located below the hypothalamus, and it produces follicle-stimulating hormone, leutinizing hormone and antidiuretic hormone.
- Thyroid - The thyroid gland is located in the neck near the trachea. It produces triiodothyronine and thyroxine.
- Parathyroid - The parathyroid glands are located in the neck, behind the thyroid gland. They produce the parathyroid hormone.
- Adrenal - The adrenal glands are located on each kidney. They produce epinephrine and corticosteroids.
- Pineal - The pineal gland is located in the center of the brain, and it produces melatonin.
- Pancreas - The pancreas is located in the abdomen, and it secretes insulin and glucagon.
- Gonads - These are the sex organs. The testes produce testosterone, and the ovaries produce estrogen and progesterone.
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Functions of Hormones
This list of endocrine system facts includes the functions of each hormone:
- Thyrotropin-releasing hormone - It stimulates the production of thyroid-stimulating hormone and prolactin from the anterior pituitary gland.
- Dopamine - It inhibits the release of prolactin from the anterior pituitary gland.
- Oxytocin - It stimulates the production of breast milk and increases uterine contractions.
- Follicle-stimulating hormone - It stimulates development, growth and reproductive processes.
- Leutinizing hormone - It triggers ovulation and the production of testosterone.
- Antidiuretic hormone - It controls the reabsorption of water in the kidneys.
- Triiodothyronine - It regulates body temperature, heart rate, metabolism, growth and development.
- Thyroxine - It regulates metabolic processes and physical development.
- Parathyroid hormone - It increases the concentration of calcium in the blood.
- Epinephrine - It increases heart rate, constricts blood vessels and opens air passageways.
- Corticosteroids - These hormones regulate carbohydrate, protein, and fat metabolism and control the reabsorption of sodium in the kidneys.
- Melatonin - It regulates the sleep-wake cycle.
- Insulin - It regulates the absorption and storage of glucose.
- Glucagon - It regulates the release of glucose into the bloodstream.
- Testosterone - It promotes muscle growth and body hair.
- Estrogen - It promotes breast development and regulates the menstrual cycle.
- Progesterone - It prepares the endometrium for implantation and decreases the body's immune response.
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Diseases of the Endocrine System
There are several diseases which affect the endocrine system:
- Diabetes - High blood sugar levels caused by inadequate amounts of insulin or the inability of cells to absorb insulin.
- Hyperthyroidism - Too much thyroxine or triiodothyronine in the blood, leading to weight loss, increased heart rate and irritability.
- Hypothyroidism - Not enough thyroxine or triiodothyronine in the blood, leading to poor muscle tone, fatigue and slow speech.
- Cushing's Syndrome - Too much cortisol, a type of corticosteroid, in the blood. It causes weight gain, muscle loss and fragile skin.
- Addison's Disease - Not enough steroid hormones in the blood. Weakness, loss of appetite and low blood pressure are the symptoms.
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1. "Pathophysiology of the Endocrine System." Colorado State University. http://www.vivo.colostate.edu/hbooks/pathphys/endocrine/index.html
2. "Endocrine System." Biology at Clermont College. http://biology.clc.uc.edu/courses/bio105/endocrin.htm
3. "Endocrine System Diseases." The Hormone Foundation. http://www.hormone.org/endocrine_system_diseases.cfm