Quoting: Do Not Use! Natural or Desiccated Thyroid (ARMOUR THYROID) For Thyroid Hormone Replacement Therapy - Worst Pills, Best Pills Newsletter May, 2003 We decided to revisit the Do Not Use status of Armour Thyroid because,remarkably, it remains among the Top 200 drugs in the U.S., with almost 2 million prescriptions dispensed in 2002. And the number of prescriptions appears to be growing. Armour Thyroid is made from desiccated pork thyroid glands and is sold by Forest Laboratories, Inc. of St. Louis. The Medical Letter on Drugs and Therapeutics, an independent source of drug information written for physicians and pharmacists that we frequently cite, concluded that synthetic levothyroxine is preferred over other forms of thyroid replacement drugs. This recommendation was made in 1977. Food and Drug Administration (FDA)-approved levothyroxine products include Thyro-Tabs, Novothyrox, Unithroid and Synthroid. The AMA [American Medical Association] Drug Evaluations 5th edition -- an excellent source of drug information before the AMA became the American Merchandising Association -- also made the recommendation in 1983 that synthetic levothyroxine is the preferred thyroid hormone replacement treatment. The USP long ago established standards for all thyroid products from animal sources sold in the US, but those standards are based only on iodine content and not potency. Active thyroid hormone contains iodine and the USP standards require that the natural preparations contain between 0.17 percent to 0.23 percent of iodine by weight. However, there is no requirement for the potency of these products in regulating metabolism -- the main function of thyroid hormone. A preparation may satisfy the USP iodine requirements and not contain sufficient amounts of the active forms of thyroid hormone to produce the desired therapeutic effect. The American Thyroid Association clearly states on its Web site: There is no evidence that desiccated thyroid, a biological preparation, has any dvantage over synthetic thyroxine. Why, after over 25 years of advice to the contrary, is Armour Thyroid in the Top 200 most frequently prescribed drugs in the U.S.? One explanation appears to be that thyroid replacement therapy with natural thyroid appears to have become a niche market for unscrupulous complementary and alternative medicine (CAM) practitioners, some of whom are licensed MDs. Some of these CAM practitioners are also promoting natural thyroid hormone as a part of their weight loss programs. This is a dangerous practice, but it is not new. The Armour Thyroid professional labeling also contains this additional statement: The use of thyroid hormones in the therapy of obesity, alone or combined with other drugs is unjustified and has been shown to be ineffective. The symptoms of excessive thyroid hormone intake include chest pain, increased pulse rate, palpitations, excessive sweating, heat intolerance, or nervousness. If you experience these symptoms while taking thyroid hormone, either natural or synthetic, contact your doctor immediately. What You Can Do If you are offered natural thyroid hormone replacement treatment for any reason, this is a red flag and you should get a second opinion.