Those Mysterious Ductless Glands
IMAGINE a tightly knit business syndicate. The eight key members are in constant contact with one another by wire and by personal meetings. Each member has his own field of responsibility—one, with growth; one, with volume of sales; one, with troubleshooting; one, with competition; one, with research; one, with advertising, and so forth. Not only that, but each provides an intricate system of checks and balances within the organization, prodding this member to heighten activity and that one to a slowing down of production. And all work under the invisible control of a mysterious master whom they hear but never see.
The human body’s system of ductless or endocrine glands is something like that. These eight glands manufacture immensely powerful chemical compounds called hormones (from the Greek hormōn, meaning “arouse to activity”). These chemicals enter the bloodstream by absorption, and not through ducts such as are used by sweat or salivary glands. Hence their name ductless or endocrine, which means “secreting internally.”
These secretions or hormones then enter into the body’s chemistry, causing wonderful things to happen. Estrogen, from the ovaries, turns a girl into a woman at the proper time. Progesterone from the same glands telegraphs the order for the womb to lie still and docile, ready to serve as incubator for the fertilized egg if one comes along. Insulin from the pancreas controls the change of body sugars to energy. Pituitary secretions regulate growth of the skeleton. Too much, a giant; too little, a dwarf. Adrenaline influences skin pigmentation, blood pressure, and so on.
One of the amazing qualities of the glands is economy. The endocrine glands themselves are tiny—the four parathyroids in the throat being hardly larger than wheat seeds, and the pituitary in the brain being the size of a large pea. Not only the size of the gland, but the amount and potency of the secretion, is an example of chemical economy. The adrenals secrete about a teaspoonful in a whole lifetime. And the amount of thyroid secretion per day is too small to be weighed by ordinary instruments.
The Lesser Four
There are four that seem to be somewhat less important than the other four in our chemical syndicate. One of the lesser four is the pineal gland, which lies behind the pituitary in the brain. Its specific functions are still vague, though it apparently affects sexual development.
The parathyroids, attached to the thyroids in the throat, regulate the calcium and phosphorus content of the blood. They seldom act up, but if not enough hormone is produced by these glands, the concentration of calcium in the blood falls and the amount of phosphorus rises. Then a person may become nervous and suffer from muscle spasms and convulsions. The parathyroids are tiny beads of glands, usually two on each side of the windpipe. Though being the smallest of the endocrine glands, they are necessary for the life of the organism. If they are removed, death results from tetany or muscle spasms unless calcium is given.
The thymus is a double gland in the upper chest. Composed of spongy tissue, it directs the body’s defenses against germs. After puberty it remains about the same size, but becomes fatty in structure and apparently nonfunctioning.
“For a child without a thymus,” reported Newsweek magazine, “the situation is grim.” Although extremely rare, it is said that a child born without one will die of an overwhelming infection by the age of two. Thus the thymus evidently plays an essential role in the development of antibodies for the baby’s protection against disease.
The pancreas secretes insulin to control the use of sugar by the body. If it fails, sugar accumulates in the blood and spills over into the urine, and the patient suffers from diabetes.
Four of Greater Significance
The sex glands are important, but not essential to life. The female ovaries, besides their primary function of producing egg cells (perhaps 50,000 in a lifetime), manufacture two hormones, estrogen and progesterone. During a woman’s entire period of fertile years only a few milligrams of estrogen are secreted, yet this is enough to transform a girl into a woman, and to regulate the release of a mature egg in the reproductive cycle approximately once a month.
Experimental science has discovered that female hormones help to reduce artery hardening in both sexes. Undoubtedly the body uses sex hormones in other roles than those of reproduction.
The male testes, besides producing sperm, secrete the hormone testosterone, which plays a part in the body’s use of protein, in bone healing, and in blood clotting.
The pituitary, situated at the base of the brain, is the master chemist. It secretes at least eight active compounds. One of these is related to the entire reproductive arrangement in the female—the maturation of the egg in the Graafian follicle in the ovaries, the manufacture of estrogen, the menstrual cycle, the secretion of prolactin to promote milk for the newborn child, and so on.
Another pituitary hormone regulates growth. Another stimulates the thyroid gland. Another the adrenal. Another regulates the transfer of fat deposits to the liver. Another regulates skin color. Another regulates the volume of urine excreted daily, and the body’s salt balance. What a versatile and precise chemical master the pituitary is!
The thyroid is the body’s gas pedal! It speeds up or slows down the rate of living. If too little thyroid activity occurs, both physical and mental vigor decreases. There may be dry skin, loss of hair and super-sensitivity to cold. On the other hand, if too much, nervousness, weight loss in spite of increased appetite, inability to withstand heat, and heart pounding may result. In addition, if thyroid deficiency in the mother occurs during pregnancy, the unborn child may become a cretin, retarded in growth and sexual development.
The thyroid, the largest ductless gland in the adult, makes an iodine-containing hormone that affects the rate at which the body transforms food into energy. If not enough iodine is present in the diet to serve the thyroid’s function, enlarged thyroid or goiter often results. That is why many salts are iodized, to prevent such deficiency.
The adrenal glands are crowns resting on top of the kidneys, one above each kidney. There are two parts to the adrenals, the adrenal medulla (inner core) and the adrenal cortex (outer shell). The adrenal medulla secretes what has been called the “emergency hormone”—epinephrine (adrenaline)—into the blood, enabling the body to adjust to sudden stresses. Healthy adrenal glands enable the body to cope with emergencies. If a man has to escape from an attacker, his heartbeat and rate of oxygen consumption increase, the index of awareness goes up, blood-clotting time goes down. The adrenal medulla is the crisis captain!
The adrenal cortex, which is essential to life, apparently produces more than three dozen hormones, all of them steroids. These hormones serve in many ways, such as helping to regulate salt and sugar balances in the body and exerting an anti-allergic and anti-inflammatory action.
Among the marvelous things made that reflect the precise and intricate work of a master Designer are those amazing ductless glands, which, like the chemical syndicate they are, regulate so perfectly the functions of the human body. It is more believable that a watch, complicated as it is, made itself by chance, than that the infinite complications of the endocrine system should have just happened, and especially so since all the glands must function from the start, perfectly, if the body is to live normally or even live at all!
[Box on page 19]
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TABLE OF ENDOCRINE FUNCTIONS
GLAND LOCATION SOME FUNCTIONS RESULTS OF MALFUNCTION
Pineal Brain Aid to sexual maturity Abnormal sex
Pituitary Brain Regulates skeletal Oversecretion:
growth, skin color, giantism,
the salt balance abnormal sexual
and has a controlling development
influence over most Undersecretion:
of the body’s organ dwarfism,
Thyroid Throat Regulates body Oversecretion:
(near metabolism nervousness,
Adam’s weight loss,
apple) heart pounding
Para- Near Regulation and Oversecretion:
thyroids thyroid maintenance calcium level rises,
of normal blood possibly causing
calcium level kidney stones
Thymus Upper Defense against Susceptibility
chest germs to infections
Pancreas Abdomen Produces insulin, Oversecretion
(behind which controls of insulin:
stomach) the change of low blood sugar
body sugars to Undersecretion of
energy; also insulin:
produces diabetes mellitus
Adrenals Top of Enables body to Difficulty in
kidneys adjust to coping with
sudden stresses; emergencies
provides and in adjusting
anti-inflammatory to the stresses
and anti-allergic of living
Gonads Male: Testes produce Sterility and
(testes, Scrotum sperm and numerous
ovaries) Female: male conditions
Pelvis characteristics; relating to
ovaries produce sexual development
eggs and female
[Chart on page 17]
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