Category : Brain
I am a pinkish, pea-size nubbin of tissue. I hang, like a cherry, on a tiny stem from the underside of your brain. I weigh only about half gram and 85 percent of that is water. But after your brain I am probably the most complex organ in your body. I play a key role in almost everything that you do. The all important hormones that I secrete can work wonders or wreak havoc. I can let you live a perfectly normal existence, I can sicken you with a bizarre spectrum of diseases or I can kill you. It was one of my hormones that gave you the initial push into the world: oxytocin started the contradictions of your mother’s womb. It was I who decided that you should be of normal size, rather than a one meter midget or a two and a half meter giant. I can shrink your sexual organs back to boy size, or so hasten your ageing process that you will be an old man in a few months’ time. I am your pituitary gland.
I have been described as your master gland, the conductor of your endocrine symphony. I take my orders straight from that prune size section of your brain called the hypothalamus, from which I hang. It is my job to monitor the activity of other glands, to see that they produce exactly the right amount of their hormones. I suppose you could call me a chemical boss of your body, and I am not bragging when I call myself the Earth’s most compact and intricate chemical plant.
I am divided into two lobes. My small posterior lobe stores two hormones produced by the hypothalamus. My much larger anterior lobe produces approximately ten hormones. These hormones are among the most complex substances known to man. My total daily output, however, is less than1/10,00,000 of a gram.
It took a long time to sneak the first of my secrets from me. For centuries, doctors thought my function an ordinary one. I was believed to be the source of nasal mucus! My elusive secretions were present in far too small quantities to be detected until the advent of modem chemistry. Now they are being found by accumulating large quantities of different animal and human pituitaries. I secrete nine hormones that regulate homeostasis.
One of my hormones manages the thyroid gland in your neck. If I secrete too much of this thyrotropic hormone, thereby setting too fast a pace for the thyroid, you would almost literally bum up. Your appetite would be huge, yet you would remain thin. On the other hand, if I were to produce too little of this hormone, you would be sluggish, puffy, dim-witted. Fortunately, I have a built-in feedback mechanism to prevent either of these things from happening.
Much of the same situation exists with your testicles. I have two hormones, which govern these glands – one by stimulating production of sperm cells and male hormone, the other by promoting growth of the duct system to transport the sperm. Incidentally, your wife has identical hormones to nudge along development of her ovaries and production of eggs. Thus, fertility and life depends on me.
For your wife, I normally secrete only enough follicle-stimulating hormone (FSH) and interstitial-cell-stimulating hormone (ICSH) to produce a single mature egg a month. If I were to go on a spree and produce too much FSH and ICSH, five or more eggs might ripen in a single month, and your wife might have quintuplets. It is the same with your testes: too little FSH and ICSH, and you would become nervous, whining and sexually apathetic; too much, and he might well become a snorting bull.
The most pervasive and plentiful of my chemicals is my growth hormone. It played its chief role in your youth, seeing to it that you followed normal growth patterns until your bone ends closed and no further height could be added. But my growth hormone may still have jobs to do for you, even though you may be 47 years old. If you break a bone, it is believed to hasten development of new bone; if you nick yourself with a razor, it is thought to hasten healing. It may well encourage growth of new tissues to replace those that have worn out. If something should happen to make me produce this hormone in excess right now, I am quite capable of doing it, growth would resume in your hands, feet, jaws. A long jaw would sprout; your nose would enlarge into a vast bulb; your hands and feet would grow enormously.
Another pituitary hormone, found only in animals so far, has fascinating possibilities for disease control. This is lipotropin, a hormone that acts as watchdog on fat deposits in the body. It has the striking capacity to move solid fat to the liver, where it is converted into glucose. Thus, if properly harnessed, my lipotropin could well be the answer to that paunch you are beginning to grow, helping to dissolve it and keep you youthfully trim.
Since I rest in a bony cradle in the center of your head, I am almost perfectly protected from injury. Yet it can happen, and results can be dramatic. Head injury, for example, could lower my production of vasopressin (the anti-diuretic hormone), which acts as a brake on the kidneys. The kidneys would go into high gear in producing urine, perhaps gallons of it a day. To survive, of course, you would have to drink the same amount of water, something you would have no trouble doing since a constant, raging thirst accompanies this condition.
While injury to me is rare, tumors are less so. And the range of effects of these tumors can be startling. Suppose a tumor should cause me to produce too much of the hormone ACTH, which monitors the hormonal activities of the two adrenal glands sitting astride your kidneys. You would develop a great paunch of abdominal fat and another fat pad would appear on your neck and upper back. Your legs would look ridiculously spindly. Blood pressure would soar, sex drive disappear.
Calcium would drain from bones; your spinal vertebrae might collapse. Amid all this wreckage, your heart would labor ever harder, and would eventually give up. To forestall this, doctors might decide to try to slow me down with radiation; or they might remove your adrenal glands. Then, of course, you would have to be dosed with hormones continually.