The Adrenal Glands

Latin scholars will know immediately where to look for the adrenal glands. For the rest of us, the translation should not be too difficult. In Latin, ad means "toward" or "near," and ren means "kidney." In this case, ad means very near. One adrenal gland perches atop each kidney like a triangular ski hat. Each gland is composed of two parts that produce their own distinct products and operate independently of each other. You could say that the adrenal is two glands in one.

The average adrenal gland weighs less than one-fourth of an ounce, or about five grams. It is less than two inches in length and about one inch wide. About 80% of the gland is composed of a yellowish outer section called the cortex. The inner portion is called the medulla. Like the thyroid, the medulla is saturated by blood vessels, which give it a deep red color.

The adrenal cortex

Of all the glands, none is more crucial than the adrenal cortex. Without the ability to adapt to constant change, the human body would perish. And if not for the hormones of the adrenal cortex, even the slightest change or stress would prove lethal.

The pituitary controls the delicate operation of the adrenal cortex by regulating ACTH secretion. The adrenal cortex itself manufactures as many as 30 different hormones. These can then be divided into three types of hormones, all of which share the similar structure of the steroid. Each of these steroids derives from the same cholesterol origin. Although "healthy heart" advocates have given cholesterol bad press, its presence in reasonable amounts is actually crucial to the production of these cortex steroids, or corticosteroids.

The adrenal cortex is composed of three specialized layers, or zones. From the outermost to the deepest inner layer they are respectively called the zona glomerulosa, zona fasciculata, and zona reticularis. The following discussion of the adrenal cortex will be divided into a description of the function and structure of each of these zones.

The glomerulosa
Aldosterone is the primary hormone secreted in the outer layer, or zone glomerulosa, of the adrenal cortex. The level of aldosterone in the blood has a direct effect on the functioning of the kidneys. As aldosterone levels rise, the body retains salt and excretes potassium. The additional salt, or sodium, causes fluid retention; hypertension may result if excessive levels of aldosterone are maintained over a long period of time. Fortunately the body has several fail-safe techniques to counteract this. When sodium levels become excessive, chemical signals are sent to the kidneys to stop them from reabsorbing the circulating sodium. Excesses are then excreted in the urine.

The fasciculata
All it takes is a really bad case of poison oak, or an encounter with a medicine or food that causes huge red welts to appear on the skin, or a horrifying moment when the throat begins to close up and breathing becomes difficult, and one is likely to retain vivid memories of the healing power of cortisone. This miraculous drug is made from cortisol, the hormone produced in the zone fasciculata, or central section, of the adrenal cortex. An injection of this steroid can bring a severe allergic reaction under control literally in seconds. In pill form, cortisone is widely used to treat many serious illnesses, such as bronchial asthma, rheumatoid arthritis, and ulcerative colitis. As a cream, it heals a wide range of skin conditions.
Normally, the body secretes about 20 milligrams, or two-thirds of an ounce, of cortisol a day. This is nearly 200 hundred times the production of aldosterone. Cortisol regulates ACTH secretion, maintains blood pressure, regulates fluid levels, directs the metabolism of protein and glucose, increases or decreases body fat, and affects the immune system. Under extreme stress, the adrenals immediately begin pumping cortisol into the body. The output of cortisol can reach up to 20 times its normal production. This provides the body with emergency supplies of energy. Cortisol literally cannibalizes amino acids from muscles and fat from tissues. The metabolism goes into overdrive, and the immune system backs off. Stores of energy are readily at hand.
These transformations are very effective if one is combating a serious internal injury or facing a specific physical threat from the outside world. However, the day-to-day emotional stress of modern life can also cause an abnormally high secretion of cortisol. And if a person remains in a continual state of alert, serious stress-related disorders may develop.
Excessively high levels of cortisol can also lead to a condition known as Cushing's syndrome. This is often the inadvertent consequence of treating an ailment with cortisol itself. Cushing's syndrome also frequently results from a malfunctioning pituitary that is putting out far too much ACTH. Yet another reason for the overproduction of cortisol is the growth of pituitary tumors, which may call for surgical removal.
Patients with Cushing's syndrome exhibit an array of visible symptoms. Obesity is common. Often the face gets so fat that it appears to be round. The trunk of the body also takes on weight, its excessive fat frequently forming what is commonly called a "buffalo hump." Bones become very weak, and disabling back problems are frequent. Abnormally high blood glucose and diabetes can result. Hypertension is frequent. Muscle weakness and a propensity to bruise are also common. From the severity of these reactions, it is obvious that medical professionals must monitor long-term cortisol treatments with extreme care.
It is also important that patients taking these medications be slowly weaned from them. During the course of treatment, the increase of cortisol alters several crucial bodily functions. The hypothalamus receives a signal causing it to shut down its production of ACTH. This in turn deactivates the adrenal cortex, whose production of hormones stop. Therefore, the dosage of cortisol must be gradually decreased to allow sufficient time for the reactivation of these hormones. If cortisol treatment is suddenly halted, cortisol levels may become dangerously low. This can lead to a greater risk of infection as well as to general weakness and weight loss. Until the adrenals kick in and begin producing hormones again, they cannot react, even to a minor crisis. A minor illness or injury might lead quite suddenly to an unexpected death.

The reticularis
The innermost zone of the adrenal cortex, the reticularis, produces the sex hormones androgen and estrogen. The primary source for these hormones is not the adrenal glands but rather the gonads. The adrenals do play an important role, however, by providing men with some of the "female" hormone and women with some of the "male" hormone.
Although estrogen has little known effect in men, androgen's effect on women is more apparent. At puberty, it causes a variety of changes. Girls begin to grow pubic and underarm hair. Their voices may get somewhat deeper, and the first awakenings of sexual desire may begin. On the downside, androgen is also thought to be the culprit that encourages teenage acne.

The medulla

The inner section of the adrenal glands is known as the medulla. For those who have been wondering where adrenaline has been keeping itself, this is where it resides. The medulla secretes two hormones: epinephrine, commonly called adrenaline; and norepinephrine, better known as noradrenaline. Adrenaline is both the more potent and much more prevalent of the two, making up 80% of the medulla's hormones.

Nerve impulses excite the medulla to pump adrenaline and noradrenaline into the bloodstream. If you have ever been startled by a door slamming, very nearly run over by a truck, or followed down a dark street, you know exactly what a surge of these hormones feels like. Your heart begins racing. Your breath comes faster. You are suddenly and intensely alert. Within seconds, your entire muscular system is capable of extraordinary feats. Your body has prepared you to either stand up to the emergency situation or physically remove yourself from it.

In 1931, Dr. Walter Cannon of Harvard University formulated the emergency theory of adrenaline secretion. While running experiments on a cat, he noticed that when the animal was calm, the blood circulating out of the adrenal gland was normal. When a dog was allowed into the laboratory, however, the cat's hormonal balance was significantly altered. Sudden secretions of adrenaline surged into its circulating blood.

Adrenaline and noradrenaline work in conjunction with the adrenal cortex hormone, cortisol. These are the main stress hormones. Under emergency conditions, they provide instant readiness for unusual physical demands as well as the energy needed to fulfill them. Although these hormonal reactions are extremely useful as a survival mechanism, problems can arise if this response is initiated too frequently.

Unfortunately, in modern society people are often subjected to an immoderate amount of daily stress, and the body may react to this stress as to an ongoing mini-emergency. Although a deadline, a traffic jam, a missed appointment, or a final exam is rarely a life-and-death situation, many people become extremely agitated about such common occurrences.

Those people who live their entire life in a crisis mode fall into the category of what is called the "type A" personality. They always seem to be in a hurry and are continually under a lot of stress. They are generally impatient, preferring to be in complete control of a situation rather than delegating responsibility to someone else. They often say they work best under pressure.

The long-term consequences of such heightened hormonal activity can be very serious. The nearly constant release of stress hormones puts excessive demands on the body. The immune system can become depressed, leaving the body more susceptible to infections and disease. The cardiovascular system may be damaged by frequent and prolonged increases in blood pressure. This increases the risk of a heart attack or stroke. Current medical research shows that prolonged stress can also contribute to cancer, anorexia nervosa, suppressed growth, and diminished sex drive. The recognition and control of this behavior could save the life of a type A person.

Some research appears to link stress to loss of brain cells as well. Some scientists feel this may account for the rapid rise in Alzheimer's disease in modern society. This disease, which generally affects men and women who are 50 or older, is characterized by a progressive loss of mental ability, memory lapses, and extreme confusion.

Although the adrenal cortex and medulla work together to handle stress, there is an important difference between them. Unlike the adrenal cortex, the medulla is not a prerequisite to survival. The adrenal cortex responds primarily to pituitary stimulation, whereas the medulla responds to electrical messages sent directly from the nervous system. Fortunately, the nervous system can also do the work of adrenaline and noradrenaline in an emergency situation. At the same time as it excites the adrenal medulla, it telegraphs direct messages to the heart, lungs, and other vital organs. This provides an important fail-safe system. Even though the effects of these nerve impulses are 10 times weaker than those of hormonal messages, hypo function of the adrenal medulla can be ruled out as a serious problem. In contrast, hyper function, which is most frequently caused by a tumor, must be treated. In such a case, either surgery or long-term drug therapy can prove effective.