While many of the low-thyroid stories we hear about involve low energy, depression, weight gain, and loss of libido, there are other tales to be told. For example, when you leave the driveway in the morning, do you pause for a moment, not knowing whether to turn right or left? Or imagine yourself later wandering around in a brain fog, not knowing where you are until you reach the perimeter of the parking lot, and then discovering that you can't remember where you parked your car. When you finally locate it, you can't find your keys! Not only has your memory slipped, you realize, it has apparently escaped.

No . . . Alzheimer's disease has not come knocking at your door (or on your head). You're too young - it's still decades before age-related memory impairment should leave its unwelcome calling card. Then what could possibly be wrong? You can take some comfort in knowing that your experience of a taste of dementia is but one of many untold stories by people just like you.

For someone who has experienced brain fog - the temporary loss of short-term memory, including, perhaps, where you are and what you're doing - the effects are something like being kidnapped. Your mind is taken from your body by a sinister force and held for ransom. But with what kind of currency can you pay to get it back? Read on.

Who could know, other than an endocrinologist, that the cause of this type of problem can be a malfunction in the biochemical signaling system coordinated by the thyroid gland, causing important regulatory messages to be delayed or sent to the wrong address? Who would suspect that the cause of this type of dementia may be an insufficiency of thyroid hormone?

Can low thyroid affect memory and even result in dementia? The scientific evidence on this point has not been clear. Earlier studies have shown that cerebral metabolism is affected by low thyroid,1 but although physicians specializing in the endocrine glands have known that this condition is characterized by memory loss, there have been few, if any, reliable studies to prove it.

The importance of thyroxine (one of the principal thyroid hormones, called T4 for short) for the development of the brain and its intellectual capacities is well known, but not for memory maintenance. In a Danish study, researchers have found that, while the clinical symptoms of hypothyroidism (low thyroid) vary considerably, cognitive deficits and psychological symptoms may be more common than previously supposed.2 In reviewing the available literature on hypothyroidism, cognitive function, and dementia, these scientists found evidence to support the idea that thyroxine can improve or reverse dementia in patients with low thyroid.

On the other hand, there have been several prospective intervention and follow-up studies of thyroid deficiency that do not support the belief that it is causally related to dementia. This is unfortunate, because the recent introduction of acetylcholinesterase inhibitors (compounds that block the enzyme responsible for limiting the amount of the neurotransmitter acetylcholine) in treating the dementia of Alzheimer's disease has sparked new interest in this matter by indicating a possible "missing link" between low thyroid and Alzheimer's. For example, there is indication that the receptors for thyroid-stimulating hormone are overexpressed in the brains of Alzheimer's patients, resulting in inadequate supplies of thyroid hormone.3 Also, it has been observed that cholinergic neurons, which are affected in Alzheimer's disease, are subject to regulation by an interaction between thyroid hormone and neural growth factors.4

Thyroid hormone was
found to have a significant
positive correlation with
measures of overall cognition.

When researchers have ignored the conventional wisdom of "no connection" between hypothyroidism and Alzheimer's and have given thyroxine to dementia patients after conventional treatment for Alzheimer's has failed, the result has sometimes been a reversal of the symptoms. This proves the valuable point that the simplest solution is often the best one, i.e., thyroid-related memory decline is easier to confirm or rule out than Alzheimer's.

The cognitive effects of two thyroid hormones, T4 and T3, were evaluated in 44 older men with a mean age of 72 and apparently normal thyroid function.5 A broad battery of standard intelligence and memory tests was used, with regression analysis to correct for the effects of age and education. T4 (thyroxine) was found to have a significant positive correlation with measures of overall cognition. T3 was not positively associated with general cognition in these healthy elderly men.

As we age, our thyroid production tends to fall, but we are learning that hormone replacement with a simple standardized supplement may be quite valuable.* While there can be no guarantees, supplementation is consistent with the overall idea that declining metabolic functions characterize aging. But they don't have to. Furthermore, because the fatigue, lethargy, and symptoms involving deficits in mentation and memory tend to sneak up on us, it may be a good idea to anticipate their arrival by taking a natural, whole, balanced thyroid supplement.

*See the following articles in Life Enhancement:


  1. Smith CD, Ain KB. Brain metabolism in hypothyroidism studied with 31P magnetic-resonance spectroscopy. Lancet 1995 Mar 11;345(8950):619-20.
  2. Fylkesnes SI, Nygaard HA. Dementia and hypothyroidism. Tidsskr Nor Laegeforen 2000 Mar 20;120(8):905-7.
  3. Labudova O, Cairns N, Koeck T, Kitzmueller E, Rink H, Lubec G. Thyroid stimulating hormone-receptor overexpression in brain of patients with Down syndrome and Alzheimer's disease. Life Sci 1999;64(12):1037-44.
  4. Hayashi M, Patel AJ. An interaction between thyroid hormone and nerve growth factor in the regulation of choline acetyltransferase activity in neuronal cultures, derived from the septal-diagonal band region of the embryonic rat brain. Brain Res 1987 Nov;433(1):109-20.
  5. Prinz PN, Scanlan JM, Vitaliano PP, Moe KE, Borson S, Toivola B, Merriam GR, Larsen LH, Reed HL. Thyroid hormones: positive relationships with cognition in healthy, euthyroid older men. J Gerontol A Biol Sci Med Sci 1999 Mar;54(3):M111-6.

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