All people, and animals, too, have glands that influence or control how their organs function. These glands are called endocrine glands, and they are located in many different places throughout the body.
An endocrine gland makes a chemical substance called a hormone, which it supplies directly into the bloodstream. The hormone travels through the blood vessels to parts of the body where it acts upon organs and influences how they work.
Removal of the thyroid gland is a simple and safe operation. The scar from the horizontal incision is just a thin line and usually fades out as the child gets older.
Hormones from the anterior portion of the pituitary control many body functions. The most important hormones are the growth hormone, the hormone that affects the activity of the adrenal glands, and the hormones that stimulate other glands like the thyroid and the testicles and the ovaries. When these glands are stimulated, they secrete their own hormones into the bloodstream.
To give an example: The pancreas, located in the upper part of the abdomen, manufactures the hormone insulin. When insulin is supplied by the pancreas, it travels in the bloodstream and controls how we use the sugar that we have eaten. Since the insulin goes to all parts of the body, it regulates the use of sugar whether it is in the brain, or in the liver, or in the muscles. Without insulin, we couldn’t use the sugar for the energy we need. Our brain, our liver, and our muscles would all fail to work properly as they require a great deal of sugar.
The endocrine glands are:
The Pituitary Gland
Located at the base of the brain, this is a tiny gland, no bigger than an ordinary thimble. But it is the “master gland” of the body because it directs all the other glands that we have. The pituitary gland makes several hormones. The main ones are:
1. The growth hormone, which determines how little or how much we will grow. If a child’s pituitary gland isn’t working right and fails to manufacture enough growth hormone, that child may not grow properly and might even become a dwarf. If the pituitary makes too much growth hormone, that child might become a giant.
2. The gonadotropic hormone, which influences the ovaries in a girl and the testicles in a boy. This hormone doesn’t really do its main work until a child reaches about twelve years of age. Then, in a girl, it stimulates the ovaries and the girl starts to undergo changes into becoming a young woman, or, in a boy, it stimulates the testicles and the boy starts to develop into a young man. Without sufficient gonadotropic hormone, a child’s adolescence may be delayed. In¬stead of beginning to mature at twelve or thirteen years of age, a child might not begin to grow up until he or she reaches fifteen, sixteen, or even seventeen years of age.
3. The thyrotropic hormone, which regulates the function of the thyroid gland. If too little of this hormone is manufactured, the thyroid won’t work properly and a child’s growth might be stunted. Such children are called cretins; they are short, fat, and sluggish, and their minds don’t work well, either.
4. ACTH. If not enough ACTH is manufactured, then the adrenal glands above the kidneys won’t function properly.
5. ADH, which controls the amount of water our kidneys excrete. If the pituitary fails to make enough of this hormone, tremendous amounts of urine are excreted. People with this condition drink huge amounts of water all the time. They never seem able to drink enough to make up for all the water they are losing through their urine.
Overactivity of the pituitary gland will cause abnormal growth and very early development, as can be seen In this comparison of two 9′h year-old girls.
Scientists have learned how to make most of the pituitary hormones right in a chemical laboratory. And so, if someone’s pituitary gland doesn’t produce enough of one of its hormones, that person can be given the hormone in a tablet or an injection. In that way, it is often possible to overcome the shortcomings of the pituitary gland. And if the pituitary manufactures too much hormone, it can sometimes be controlled by giving X-ray treatments to the gland to slow down its activity.
The Thyroid Gland
This gland is located in the neck, in front of and on the sides of the wind¬pipe. Like the pituitary gland, it, too, is extremely important. The thyroid makes a hormone called thyroxin. Thyroxin, when it gets into the bloodstream, regulates how our food is turned into energy and how quickly and completely that energy is used up.
The thyroid is also concerned in regulating our muscle activity, our body growth, and our body heat.
Even though the thyroid gland itself may be perfectly normal, it won’t work properly unless it receives a sufficient amount of thyrotropic hormone from the pituitary gland.
People whose thyroid secretes too little hormone have little pep or energy, their muscles are flabby, they get fat and lazy, they feel cold even in warm weather, and their minds function poorly. Very often, poor functioning of the thyroid gland can be controlled by giving the person thyroid pills.
People whose thyroid manufactures too much hormone will lose weight even though they eat a lot, their hearts will beat faster than they should, their hands may shake when they pick up something, their eyes may bulge, and they may have a swelling in the neck because the gland has become enlarged. (The enlargement of the thyroid gland is called a goiter.) Quite often, an overactive thyroid can be controlled by giving the person certain medicines, such as antithyroid pills, or by giving him radioactive iodine to chink. If these medicines don’t slow down the thyroid, it is sometimes necessary to operate and remove the overactive part of the gland. Operations almost always cure the condition.
The endocrine glands secrete hormones that are responsible for controlling many body functions, and they also play an important part in seeing that the body’s chemical reactions are well balanced. The main glands are the pituitary, the thyroid, the parathyroids, the pancreas, the adrenals, the testicles and the ovaries.
The Parathyroid Glands
These are four pea-sized structures lying in back of the thyroid gland in the neck. Although they are located right next to the thyroid, the parathyroid glands have an entirely separate function. They manufacture a hormone called parathormone. Its job is to regulate what happens to the minerals calcium and phosphorus that we get in our diet. For example, milk has loads of calcium and phosphorus.
A person whose parathyroids secrete too much parathormone will have a poor appetite, may be nauseated and throw up, will lose weight, and may develop a great thirst.. Also, his bones will get very brittle and will break easily. Such a person may also develop stones in his kidneys.
Sometimes the parathyroids become too active, because the child doesn’t get enough vitamin D in his diet. This can be corrected easily by taking vitamin D pills or drops. Once in a while, a swelling or tumor of the parathyroid glands develops, and in order to cure the patient, it is necessary to operate and remove the tumor. This can be done without too much trouble.
A person whose parathyroid glands don’t manufacture enough hormone will have muscle cramps, stiffness in the arms and legs, tingling in the fingers and toes, and may even have a convulsion. This condition is called tetany. In most cases, tetany can be controlled with large doses of vitamin D and calcium. Children who drink enough milk and take their vitamins regularly seldom have trouble with their parathyroid glands.
The four parathyroid glands are located behind the thyroid gland. Two are shown here. A parathyroid tumor may cause overactivity of the gland, but this is rare in children.
The Adrenal Glands
The adrenals lie on top of the kidneys, one on each side, on the back of the abdomen, high up under the ribs. They have almost as many different jobs to perform as the pituitary gland, but they can’t function properly. unless they receive the right amount of hormones from the pituitary gland. Here are some of the many jobs the various adrenal hormones perform:
The adrenal glands are located on top of each kidney, as seen in this diagram. They secrete adrenalin, cortisone and other hormones.
1. They make the heart beat stronger, especially during times when it is necessary for the heart to do extra-hard work because of strenuous exercise. The hormone they supply to make this possible is called adrenalin.
2. They overcome muscle tiredness, so that people can continue to do physical work or strenuous exercise.
3. They cause certain blood vessels to contract so that blood which would ordinarily go to those parts of the body, can go to other parts of the body where it is more urgently needed.
4. They increase the amount of sugar in the blood. This makes more sugar available to be used for energy.
5. They control the amount of salt and water in the body, sometimes causing us to hold more water and salt, at other times causing us to get rid of extra water and salt.
6. They are partially responsible for the development of a girl into a woman, and for a boy into a man. (These hormones have much the same function as hormones manufactured by the ovaries in females and the testicles in males.)
7. They are responsible for the body being able to overcome great strains and stresses. The hormone that accomplishes this is called cortisone. Without cortisone, we would not be able to live for very long.
This gland lies across the back of the abdomen beneath the stomach. Most of the pancreas is not an endocrine gland. It supplies most of the substances it makes directly to the intestines, not into the bloodstream.
But it is partially an endocrine gland because it manufactures the hormone insulin. And insulin is supplied, as all hormones are, directly into the bloodstream. In the bloodstream, insulin controls how we use the sugar we have eaten. And since insulin goes to all parts of the body, it regulates the use of sugar whether it is in the brain, the liver, the muscles, or anywhere else. If not enough insulin is manufactured, diabetes will result.
Present only in females, the ovaries lie one on each side of the uterus in the lower part of the abdomen. They are almond-shaped and about the size of large walnuts. During early childhood, the ovaries don’t secrete much hormone. When they do, a girl, no matter how young she may happen to be, may begin to show signs of maturity and will develop breasts and hair under her arms. This happens to a really young girl only once in a great while, but when it does, it usually means the girl has an important upset in gland function or might possibly have a tumor in one of her ovaries.
This diagram shows the various parts of the female organs, including the vagina, the cervix, the uterus, fallopian tubes and the ovaries. Young girls should be taught about these organs, which are responsible for reproduction.
Normally, the ovaries start to secrete large amounts of hormones when a girl reaches eleven, twelve, or thirteen years of age. These hormones are responsible for the onset of menstrual periods and for changes in the girl’s general appearance. Because of the action of the hormone estrogen, the girl’s breasts begin to enlarge, she develops hair under her arms and in the pubic region of her lower abdomen, her female organs enlarge, and her figure changes from that of a girl to that of a young woman.
The ovaries, in addition to supplying hormones to the bloodstream, manufacture eggs that can one day unite with a sperm to form a new child.
Present only in males, these are two oval-shaped glands located in the scrotal sac beneath the penis. In addition to manufacturing sperm, which can one day unite with an egg to form a new human being, the testicles make a hormone called testosterone. It is also called the male sex hormone.
The testicles don’t produce sperm or secrete very much testosterone until a boy reaches about twelve, thirteen, or fourteen years of age. Then they begin to make large amounts of testosterone, which goes into the bloodstream. This male sex hormone is responsible for the development of hair on the face, under the arms, and in the pubic region of the lower abdomen. Testosterone also influences the male organs, causing them to grow larger; it is responsible for the voice changing from that of a boy to that of a man; and it is responsible for the boy’s figure changing so that he looks more like a grown man.