Age-Related Thyroid Decline


If the human soul has a molecular structure, it is surely that of thyroxine. Why? Because this hormone, secreted by the thyroid gland, has the primary function of regulating metabolism. Without the stabilizing influence of thyroxine to keep our myriad of molecular systems in balance, we would become a metabolic disaster area, and the essence of who we are would corrode away in the ensuing chemical chaos.

Without thyroxine, our minds -- those cornucopias of thought, perception, emotion, will, memory, and imagination, all of which are the manifestations of chemical processes in the staggeringly complex neural circuitry of our brains -- would turn to sludge, and we would no longer be who we once were.

Our souls, one could argue, thus reside in the thyroxine molecule (which happens to be a somewhat unusual amino acid containing four atoms of iodine). Heresy, you say? Perhaps, but consider the following.

When a baby is born with no thyroid gland (a rare occurrence, fortunately), it is doomed, without medical intervention, to the severest form of cretinism -- profound mental retardation -- and an early death. It will have no discernible intellectual capacity and no capacity to function as a human being, lacking even such instinctive behaviors as suckling. For all practical purposes, the tiny creature, so dreadfully bereft of the characteristics we customarily associate with humanity, will be a vegetative organism, recognizable as human only by its physical form.

But physicians know that if they administer thyroxine -- a soul in a bottle, one might say -- the mental deficit is erased, as if by magic. Cretinism is prevented, and a beautiful, healthy baby emerges from the shadow of death, like a butterfly escaping a cocoon that was about to be crushed. The baby will be able to live and laugh and love and grow old. It will be fully human, with all the potential that that entails. This amazing transformation from nothingness to everything we cherish is one of the most awesome miracles of modem medicine. The man who discovered thyroxine (in 1916, at the Mayo Foundation in Rochester, Minnesota) surely deserved the Nobel Prize in medicine and physiology, and he got it -- in 1950. He was Edward C. Kendall, an American biochemist who also discovered no less than 28 of the corticosteroids, important hormones that are secreted by the adrenal cortex. Kendall ended his illustrious career as a professor of chemistry at Princeton University.

How the Thyroid System Works 
As we age, the functioning of our various endocrine glands, including the thyroid, slows down. The thyroid  gland -- a bow-tie-shaped organ located in the front of the neck, just below the larynx -- releases progressively less of the thyroid hormones that we all need for good health. Of these hormones, thyroxine (called T4 for short) is the one produced in greatest amounts; some of it is converted to the closely related compound triiodothyronine (T3), which is actually the more physiologically active of the two.

Thyroxine is synthesized from the amino acid tyrosine and the mineral iodine. Its production and secretion are controlled by the thyroid-stimulating hormone, or TSH (also called thyrotropin), which is released by the body's master gland, the pituitary. TSH is secreted in a pulsatile manner with a circadian rhythm, under the control of yet another hormone, which is released by the hypothalamus, a deep-seated structure of the forebrain. As signals reach the pituitary that more T4 is needed throughout the body, it releases more TSH, which causes the thyroid gland to step up its production and release of T4. As the T4 level rises, the pituitary is signaled to step down its release of TSH (see Figure 1). 

Figure 1: Hypothalamic-pituitary-thyroid feedback system.


Thyroid Deficiency and Widespread Dysfunction 
All of these hormones normally work together in a complicated feedback system to maintain the body's thyroid function -- and hence its metabolic rate -- within a narrow range. But, of course, things can go wrong. As we get older, it becomes increasingly likely that our hormonal control system can get out of balance.

The most common thyroid imbalance is the diminishing production of thyroid hormones, a condition called thyroid deficiency syndrome, or hypothyroidism (or sometimes just "low thyroid"). Thyroid hormones help regulate virtually every cell in our bodies. By controlling our metabolic rate, they affect thermogenesis and oxygen consumption. If their levels -- and thus, cellular metabolism -- drop too low, the result can be widespread dysfunction.

The most common symptoms of low thyroid are fatigue, dulling of mental faculties, depression, weight gain, constipation, aching joints, low blood pressure, high cholesterol, low libido, dry skin, brittle nails, hair loss, and sensitivity to cold. Most cases, it is believed, go undiagnosed because the symptoms can be easily ignored, regarded as a normal aspect of aging, attributed to something else, or not even noticed because they develop so slowly and subtly.

Thyroid deficiency most often affects women over 40, but men and even teenagers can also be affected, especially if the condition runs in the family. According to some estimates, as many as 15 to 20% of women over age 60 may have subclinicalhypothyroidism, meaning that their symptoms are sufficient to warrant thyroid supplementation but are not likely to be detected by the standard laboratory test results that most conventional doctors rely on for their diagnoses. Each year, 5 to 15% of these women develop more serious symptoms, some of which may contribute to a shortening of their lives.1-3

Long-term subclinical hypothyroidism can pose serious consequences to overall health. There  are at least two good reasons why you should want to know if you have this condition: (1) it could progress to a more serious case, and (2) it could be depriving you of vitality and longevity that are rightfully yours.

Thyroid Deficiency in Pregnancy Connected with IQ Deficit in Offspring 
If you're over 40, it is probably advisable to get a thyroid blood test to establish that you don't have overt thyroid disease. One category of women, in particular, should probably be screened routinely, namely, those who are, or are likely to become, pregnant. Why this is so has just been revealed in a research study published in the New England Journal of Medicine.4 The authors' purpose was to determine whether undetected or inadequately treated maternal hypothyroidism during pregnancy is associated with lower IQ scores in their children in the absence of hypothyroidism in the children themselves. In other words, can the mother's condition of low thyroid cause an IQ deficit in the otherwise normal child? The answer, in a word, is yes.

The researchers began by analyzing blood-serum samples that had been taken, and frozen, from 25,216 women in Maine during the second trimester of their pregnancy. The samples had been taken, for other purposes, over a 39-month period in the late 1980s. For the present study, they were analyzed for the level of thyrotropin (TSH), which is a reliable indicator of thyroid function.

The researchers tracked down and recruited 62 of the women whose serum showed strong evidence of thyroid deficiency. Of these women, 48 had not been treated for hypothyroidism during their pregnancy; the other 14 had been treated (albeit inadequately, as their frozen serum samples revealed years later), because of a diagnosis made during the pregnancy. As controls, the researchers selected 62 pairs (124 in all) of thyroid-normal women who most closely matched the 62 hypothyroid women in terms of age at delivery, gestational week when the serum sample was taken, duration of storage of the sample, number of years of education, and the sex of the child.

They then tested all 186 children, who were between the ages of seven and nine, for a variety of mental and visual-motor functions and school performance. (It had already been determined that none of the children of the 62 hypothyroid women had either transient or permanent congenital hypothyroidism.) The results were striking: the IQ scores of the 48 children whose mothers' hypothyroidism went untreated during their pregnancy were 7 points lower (which is significant), on average, than those of the control children. By contrast, the scores of the 14 children whose mothers were treated (even though inadequately) during their pregnancy were essentially the same as those of the control children.

The authors concluded that "Treating maternal hypothyroidism during pregnancy appears to be beneficial for the child, even when treatment is inadequate as determined by measurements of thyrotropin." They went on to say that "systematic screening for hypothyroidism early in pregnancy may be worthwhile, even when the degree of deficiency is mild and does not cause immediate clinical manifestations in the woman." 

Dr. Jonathan V. Wright

Thyroid Decline Often Undiagnosed and Untreated 
All in all, it seems prudent for those over 40 (especially women) to be screened routinely for hypothyroidism. It is relatively simple to diagnose overt cases, which can be confirmed by abnormal test results measuring TSH and antithyroid antibody.

Diagnosing age-related, or nonovert, thyroid decline is more problematic, however, largely because most conventional doctors are not trained to look for it.3 They are trained to focus more on lab tests than on physical or psychological symptoms. Thus, symptoms of low thyroid may be overlooked, while lab tests may be technically within normal range. To complicate matters, the symptoms of subclinical hypothyroidism (described above) are nonspecific. That is, they can arise from other causes as well. And even when they are observed, many physicians may dismiss them as  "just" part of the aging process. As a result, the condition often goes undiagnosed and untreated. It is estimated by clinical endocrinologists that about one in 20 Americans, or 13 million people, have a thyroid disorder of some kind, but about 8 million of them do not know it.

Nutritional Supplementation for Age-Related Thyroid Decline 
If you wish to improve or help prevent age-related thyroid decline and you do not have any overt endocrine disease, you may benefit from taking an antiaging thyroid supplement.

Designed to help rejuvenate the entire endocrine system, such a supplement would combine glandular extracts from thyroid, adrenal, hypothalamic, pituitary, and testicular (for men) and ovarian (or women) tissues. A whole, natural thyroid extract contains all the thyroid-function hormones: T4, T3, T2, and T1. Most prescription drugs given for thyroid replacement contain only T4.

According to Aristotle, "The knowledge of the soul admittedly contributes greatly to the advance of truth in general, and, above all, to our understanding of Nature, for the soul is in some sense the principle of animal life."

Given what it can do, thyroxine, for certain, touches the principle of life.

Dr. Jonathan V. Wright recommends thyroid supplementation for those over 40 who have no overt endocrine disease, even if they have no symptoms of thyroid decline, because all endocrine functions are beginning to slow down at this stage of life. The kind of comment he hears most often from those taking a thyroid supplement is, "I just feel a little more energetic overall. My thinking is a little clearer. I'm not quite as constipated."

Dr. Wright adds, "You might consider using a thyroid supplement as part of your antiaging program because, while it might add only 1/4 grain of the actual thyroid glandular itself, it would also nourish the rest of the endocrine network."

We agree with Dr. Wright's assessment of the benefits of thyroid extract as a dietary supplement, but we will resist (apparently with some difficulty) the temptation to call it "soul food."

A lucid overview of the benefits of whole-gland extracts vs. single hormones and of the benefits of multi-gland vs. single-gland extracts can be found in Exclusive Interview With Jonathan V Wright, MD: Endocrine Rejuvenation - Nov. 1997.

1. Anonymous. A delicate balance. Harvard Health Letter 1994;19:3-6. 
2. Anonymous. Thyroid guidelines: use newer TSH tests for early, accurate diagnosis. Geriatrics 1995;50:14-5. 
3. Kelley B. Running on empty. Health 1997;11:64-9. 
4.  Haddow JE, Palomaki GE, Allan WC, Williams JR, Knight GJ, Gagnon J, O'Heir CE,  Mitchell ML, Hermos RJ, Waisbren SE, Faix JD, Klein RZ. Maternal thyroid deficiency during pregnancy and subsequent neuropsychological development of the child. NEJM1999 Aug 19;341(8):549-55.