The Basics of Human Endocrine System
ByThe endocrine system is the name given to the glands and other tissues in the body that produce hormones. Hormones are the body’s chemical messengers and are sent to the various parts of the body to help maintain its activities and chemical balance within safe limits. They are vital to the healthy functioning of every cell. They also have an important part to play in the emotions and moods – this effect is particularly noticeable during puberty and adolescence.
Conducting the whole system are the hypothalamus (a part of the brain) and the pea-sized pituitary gland, which lies just under the brain and is connected to the hypothalamus by a short stalk. Hormones from the hypothalamus instruct the pituitary gland to pour out more, or less, of its hormones according to their levels in the blood. Many of the pituitary hormones regulate the hormone production of other endocrine glands, as well as directly affecting functions such as bone growth and water levels in the body.
The action of the hypothalamus is affected by environmental factors such as light and darkness, by sleeping and waking, and by stress and excitement.
The thyroid gland is shaped like a butterfly and lies across the voice-box in the throat. Its hormones, one of which is thyroxine, affect the body’s energy level, metabolic rate, rate of growth and sexual development.
The parathyroid glands next to the thyroid make a hormone which, together with vitamin D and one of the thyroid hormones, calcitonin, promotes calcium balance.
The adrenal glands lie on top of the kidneys. They produce several important hormones including androgens, the male sex hormones, and adrenaline, which affects blood pressure, the release of glucose from the liver and the movements of the intestine.
Insulin and glucagon are made in the pancreas, a long thin gland lying behind the stomach. Insulin is the most important of the hormones regulating the use of carbohydrates and fats by the body, and it maintains the blood sugar within normal levels. Glucagon stimulates the breakdown of glycogen (part of the body’s energy store in the liver and muscles) and the release of glucose from the liver.
Several important hormones come from the secretory cells in the kidney; they include renin, which helps control the blood pressure, and erythropoietin, which stimulates red blood cell production.
Both the ovaries and the testes manufacture increased levels of sex hormones at puberty. Hormones made by the intestine have a variety of local actions. Prostaglandins are hormones made by various organs on site which are important in many processes including inflammation, fever, blood pressure control, stomach secretions and blood clotting.
When things go wrong
Illness or abnormality follow if an endocrine gland produces too much or too little of one of its hormones. Diabetes mellitus (sugar diabetes), for example, is caused by a lack of the pancreatic hormone insulin. All the body’s cells need insulin so they can take up glucose from the blood. Normally, a rise in the blood sugar after a meal stimulates insulin production. Without enough insulin the blood sugar level rises abnormally high.
Large amounts of urine are made in order to try to get rid of this sugar load and the child has to drink much more than usual to keep up with his thirst. The body uses its fat deposits for energy ana mere is rapid weight loss and a fruity smell to the breath.
Treatment involves balancing the amount of exercise, food and injected insulin.
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