If you go to your doctor to have your thyroid tested, he or she will draw your blood and send it to the lab to obtain a thyroid panel. While the advances made in diagnosing diseases in the laboratory have been remarkable over the last decade, as can be seen in the tests for illnesses such as rheumatoid arthritis and breast cancer, lab tests for hypothyroid problems are still largely inaccurate, according to Dr. Charles Mary III of the Mary Clinic in Louisiana. Dr. Mary's position was backed up by the majority of doctors attending the recent Consensus Development Conference.
One of the breakthroughs in the last several decades has been the Thyroid Stimulating Hormone (TSH) test. When doctors first discovered how to measure this hormone, they decided that TSH was the gold standard of diagnosing thyroid dysfunction. TSH is a hormone produced by the pituitary gland in response to fluctuations of thyroid hormone. If the brain sees low levels of thyroid hormones in the body, or if a person's metabolism is poor, the brain will begin to pump out higher levels of TSH. So, according to this lab test, elevated TSH would be indicative of hypothyroid function.
According to Mario McNally, MD, an endocrinologist, and James Carter, MD, DrPH, the emeritus head of the Nutrition Section at Tulane University School of Public Health and Tropical Medicine, the problem is that a person can be very ill with hypothyroidism yet still have a normal TSH test—that is, it is still possible for someone to have hypothyroidism when his or her levels of TSH are low. When the lab work shows that TSH is in the low or normal range in these cases, the problem is that the body is not adequately converting the hormone T4 to T3. Remember, T3 is a cru cial hormone in getting oxygen into the cells and in enabling efficient metabolic function.
Factors that inhibit the body's conversion of T4 to T3 are low levels of iodine, selenium, zinc, copper, vitamin B12, vitamin B6, vitamin A, and vitamin E; high levels of fluoride; high or low levels of serum ferritin; and a diet that is too low in calories. Other factors that interfere with the conversion of T4 to T3 are beta-blockers, birth-control pills, high levels of estrogen, lithium, lead, mercury, stress, cigarette smoking, pesticides, aging, diabetes, surgery, adrenal insufficiency, and human growth hormone deficiency.
According to Dr. Mary, one of the main hormones that impairs the efficiency of the conversion of T4 to T3 is estrogen. He suggests that the widespread use of birth-control pills and hormone replacement therapy (HRT) drugs such as Premarin may be contributing to our epidemic of obesity by making it harder for the body to convert T4 to T3. As evidence, he points out that all farmers know that you can easily fatten up cows, pigs, chickens, and other animals by giving them estrogen. Dr. Mary has found that 90 percent of the patients he diagnoses with hypothyroidism are women.
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