Hypothyroidism is by far the more common of the two thyroid problems-the other is hyperthyroidism, when the body goes into overdrive-and just 10 years ago, it was considered one of the great undiagnosed diseases. But nowadays, doctors are accused of having a complete knee-jerk reaction, and are seeing thyroid problems where none exist and giving people hormone drugs unnecessarily.
"This is potentially an enormous problem, given that one in four people have their thyroid function checked," says Jayne Franklyn, president of the British Thyroid Association (BMJ, 2009; 338: b725).
As a result, patients who are wrongly being given a hormone drug such as levothyroxine could be suffering from serious effects due to an excess of thyroid hormones. Worse, the misdiagnosis could also be masking more serious conditions such as depression.
The thyroid, an endocrine gland found at the base of the neck, plays an essential role in the body's functioning and metabolism. It controls the rate at which the body burns energy and makes proteins by releasing the hormones T4 (thyrox-ine) and T3 (triiodothyronine). The thyroid may be producing either too little of these hormones (hypothy-roidism) or too much (hyperthyroid-ism). Hypothyroidism can also result from these hormones failing to reach the body's tissues.
Doctors have just two ways of diagnosing a thyroid problem: they can either look for symptoms, or conduct a blood test. However, both methods can be highly unreliable. Typical symptoms of hypothyroidism include tiredness, feeling the cold, dry skin, depression and weight gain, but these features can also be caused by a range of other health problems. Indeed, thyroid disease often mimics other, more serious, problems. Symptoms of Graves' disease, which can be caused by hyperthyroidism, are almost identical to many of the physiological changes that occur during pregnancy, making the diagnosis almost impossible in expectant mothers (Endocr Pract, 2009; Oct 15: 1-36; Epub ahead of print).
A more reliable diagnostic test is to carry out a standard blood test that measures thyroid-stimulating hormone (TSH) levels. But this can also produce false-positive results, especially if the patient has another health problem. If a second blood test were to be carried out after the true illness has been cleared up, TSH levels would probably show up as normal. Unfortunately, second tests are rarely ordered, and the patient will often already have started an unnecessary course of hormone drugs, which can have serious side-effects.
Doctors also tend to get it wrong when it comes to understanding the causes of thyroid disease. The standard view is that thyroid problems are either the result of people living longer or because of a genetic inheritance. It used to be caused by iodine deficiency but, at least in the West, so much of our food these days has been enriched with iodine that this cause has all but been eliminated. If anything, we are now in danger of consuming too much iodine, especially through iodine-enriched salt, which can lead to iodine-induced thyrotoxicosis, or hyperthyroidism (BMJ, 1976; 1: 372-5).
So, having eliminated iodine deficiency as a cause, medicine believes that the other two causes-ageing and genetics-are beyond the patient's control, and that only an outside agent such as a drug-levothyroxine for hypothyroidism and a beta-blocker for hyperthyroidism-is able to normalize the patient's hormone levels. In fact, levothyroxine is just as likely to cause an excess of thyroid hormones (Lancet, 1991; 337: 171-2).
But the above-mentioned two causes certainly don't account for most cases of thyroid disorders. Indeed, the growing evidence suggests that hypothyroidism and hyperthyroidism are more often caused by environmental factors and by diet-including, paradoxically, consuming too much iodized salt, which was originally enriched to combat thyroid dysfunction.
Other causes that doctors appear to overlook include:
o food allergies. People with multiple food allergies, such as coeliac disease, are much more likely to develop thyroid problems (J Pediatr, 2009; 155: 51-5).
o selenium deficiency. The thyroid gland has some of the highest concentrations of selenium in the body, so any deficiency in this essential trace element can lead to thyroid disease (Best Pract Res Clin Endocrinol Metab, 2009; 23: 815-27).
o pollutants. Common environ-mental pollutants such as per-chlorate, thiocyanate and nitrate suppress iodine absorption and have been found to cause thyroid disease in both animal and human studies (Toxicol Ind Health, 1998; 14: 121-58; Best Pract Res Clin Endocrinol Metab, 2009; 23: 801-13).
o cancer treatment. The healthy functioning of the thyroid can be affected by radiotherapy given for cancer (Am J Clin Oncol, 2009; 32: 150-3).
o diabetes, especially type 1, can cause thyroid problems (Turk J Pediatr, 2009; 51: 183-6).
o preeclampsia, a common com-plication of pregnancy, can affect thyroid functioning later in life (BMJ, 2009; 339: b4336).
o fluoride. This chemical in our water supply can interfere with the natural absorption of iodine (Klin Wochenschr, 1984; 62: 564-9).
o iodine excess. This element is considered to be essential for healthy thyroid functioning, but too much can lead to hyperthy-roidism (J Endocrinol Invest, 1994; 17: 23-7). Avoiding iodine-enriched salt may not be enough, as iodine is also used in cough expectorants, antiseptics, and certain drugs and imaging contrast media (Z Kardiol, 2001; 90: 751-9).
o prescription drugs. Even drugs that don't contain iodine can cause thyroid problems. These include lithium, given for bipolar disorder (manic depression), which often causes an underactive thyroid (N Engl J Med, 1995; 333: 1688-94), as does the heart drug amiodarone (BMJ, 1996; 313: 539-44).
o emotional problems. The thyroid is especially vulnerable to emotional traumas such as bereavement and divorce (Acta Endocrinol, 1993; 128: 293-6).
It's not forever
A common belief in medicine is that a thyroid problem is forever. As a result, thyroid patients will probably have to take a drug to maintain normal hormone levels for the rest of their lives. In a few rare cases, this may indeed be necessary, but the evidence suggests that it's much more likely that thyroid problems wax and wane, assuming that the patient even had the problem in the first place.
Sadly, medicine isn't geared up for such an eventuality, and often won't even take a second, confirmatory TSH blood test a few months later, when the real cause of the imbalance may have gone away, and hormone levels may have normalized.
It's also more likely that the cause of the thyroid problem is within the control of the patient, and a little detective work can often uncover the true culprit, which then can be sorted out. Often, for example, the problem is caused by environmental pollutants, especially fluoride, and these can be reduced or removed by using air and water filters. Certainly, thyroid problems can worsen as toxins build up in the body, which may lead doctors to believe that they are the direct result of ageing.
But one thing's for sure: thyroid problems are usually not 'just one of those things'. In many cases, they can be either avoided or reversed-and without the use of powerful pharmaceuticals.
WDDTY VOL 20 NO 10