I am that pinkish butterfly shaped gland that straddles your windpipe just below your Adam’s apple. I weigh about 20 grams. My daily hormone production is less than 1/2,800,000 gram. My modest size and productivity would suggest that I am not very important. Actually, I am a powerhouse. I am your THYROID.
Had my hormones been absent at the time of your birth, you would have grown into a thick-lipped, fl at-nosed dwarf- an intelligent or moron. My principal job for you today, however, is to determine the rate at which you live metabolically – whether you creep like a snail or race like a hare.
You can compare me to a blacksmith’s bellows. I fan the fi res of life, governing the rate at which your billions of cells generate energy. I can either blank the fi res or fan them into raging flames. If I produce too little of my hormones, you would probably become puffy-faced, obese, sluggish, dull-witted and, in an extreme case, even a semi-vegetable. On the other hand, if I overproduce, you would develop a wolfish appetite but become rail-thin as you will burn up your food at a rapid rate. Your eyes would pop, maybe so far that the lids could not close over them. You would feel jittery, nervous-perhaps a candidate for the psychiatric ward. Your heart would race, possibly to a point of exhaustion and death.
Like your other endocrine glands, I am a tiny chemical plant, plucking materials from your bloodstream and fitting them together to make complex hormones. My two main hormones are approximately two-thirds iodine. My daily requirement for iodine is roughly 1/5000 gram only. Yet this microscopic amount spells the difference between idiocy and healthy development in infancy, the difference between vigor and sickly lethargy ness in adulthood.
I would not trouble you with all the details of my expertness on chemistry but a few highlights might be interesting. Iodine comes to me from your digestive tract in the form of iodide. My enzymes (I have several different ones that perform various tasks) make the conversion into iodine and then hook this iodine to an amino acid within me called tyrosine. After this chemical marriage has taken place, I can then form my two chief hormones. Next, my enzymes step in again to hook molecules of these hormones to your blood proteins so that they can hitchhike to the remotest corners of your body.
The potency of my hormones is striking. A tadpole without thyroid hormone will not become a frog. My hormones stimulate virtually all the cells of your body.
Because of their power my hormones must be kept under exact control, providing only the energy needed at any given moment. When your wife was pregnant, her thyroid provided slightly more hormones than usual, to help fill her special needs. As you sleep, your energy requirements reduce. But even the slightest activity steps things up. Simply sitting up in bed boosts your energy needs considerably; standing increases it even more; really heavy exercise lifts them manifold. Heavy mental exercise scarcely raises energy requirements within your body. Half a peanut an hour would fill the need while you work on your income tax return.
Two other glands help me maintain the necessary control of my hormone production. The hypothalamus, a nubbin of tissue in your brain, stimulates the pituitary, up under your brain. The pituitary in turn produces the hormone thyrotropin, which targets on me, telling me to get to work to meet current energy needs. When I produce too much hormone, the excess shuts off the pituitary stimulus. This feedback keeps production on an even keel.
As you see, I am under nervous as well as chemical control. This explains why stress or worry may be capable of causing me to produce excessive amounts of hormone-enough to make a jittery wreck of you, enough even to put you in a mental hospital. A death in the family, business failure, a serious auto accident extensive surgery, marital trouble: pile any of these on top of another over a period of months or years, and a chain reaction gets under way. The worrying brain may cause the hypothalamus to over stimulate the pituitary, which in turn over stimulates me. I start driving you at a pace you cannot stand.
In many respects I am one of the weakest spots in your body. A great deal can go wrong with me. My controls are so precise; my hormone production is so dependent on so many other factors, that failure anywhere along the line can spell trouble.
Lack of iodine is a common cause of trouble. People in developed countries, have little problem. Seafoods and even vegetables grown in soils near the sea are rich in iodine. If these foods are not available, then the use of iodized salt can meet your iodine requirement. People elsewhere in the world are not so fortunate. In mountainous regions, iodine is almost always missing in the soil and water. The same is true in areas once glaciated; as glaciers melts, it washes away iodine out of the soil. And in many such places iodized salt is not readily available.
My response to iodine hunger is to grow larger, to add millions of new cells in an effort to capture any iodine available. My weight may shoot up from less than 28 grams to a few hundred grams. This is an iodine-deficient goitre-”nontoxic” goitre, which is disturbing as far as looks are concerned but rarely dangerous to health, unless the gland grows large enough to pinch the windpipe.
A variety of things can slow me into relative inactivity. Let the environment or certain drugs or disease knock out any or my crucial enzymes and my hormone production slows or stops. Also, for reasons not understood, I may simply decide to shut up business, to atrophy or be replaced by non functioning thyroid tissue. Or your pituitary may go on the fritz and produce too little of the stimulating hormone I need.