The earliest forms of natural thyroid came from the thyroid gland of cows, but the Armour meat company got into the field, marketing its own natural desiccated thyroid from pigs -- porcine thyroid - known as Armour Thyroid. That drug was on the market for much of the 20th century, and continues to be available today.
Because it was developed before the existence of the FDA, its legality as a prescription medication was grandfathered in, and natural desiccated thyroid, while regulated by the FDA, has never gone through the "New Drug Application" (NDA) process that is required of new drugs introduced to the market since the FDA was founded.
Natural desiccated thyroid contains both T4 (thyroxine) and T3 (triiodothyronine), as well as calcitonin, and other elements found in an organic thyroid gland. A normal thyroid gland produces primarily T4 (the storage hormone) and some T3, and the T4 is converted into T3, the active hormone, for use by the cells and tissues of the body.
During the middle of the last century, synthetic thyroid medication -- known generically as levothyroxine, and sometimes referred to by the most common brand name, Synthroid - was developed. Levothyroxine is a synthetic form of the T4 hormone. Levothyroxine became increasing popular, and during the second half of the 20th century, it became the treatment of choice by the mainstream medical community. Physicians claimed it was more stable and consistent than natural desiccated thyroid, and that the body was able to convert straight T4 into the active T3 the body needed to resolve hypothyroidism.
For several decades, the vast majority of thyroid patients were prescribed levothyroxine drugs to treat hypothyroidism. But as interest grew in natural medicine in the 1980s, holistic/integrative/complementary/alternative physicians began to again prescribe natural desiccated thyroid, which had remained on the market, although with a very small market share. Also, some of the older physicians who had previously used natural desiccated thyroid with their patients, returned some patients back to natural desiccated thyroid drugs, because those patients complained, after being switched to levothyroxine, that their symptoms had worsened or couldn't be resolved, and found that some patients simply did better on natural thyroid.
While many thyroid patients -- and physicians -- remained unaware that there were any options outside of levothyroxine to treat hypothyroidism, in the 1990s, with the rise of the Internet, and increased access to both other patients, and sharing of information among patients and practitioners, some symptomatic and dissatisfied thyroid patients on levothyroxine became increasingly aware that natural desiccated thyroid drugs were an alternative to levothyroxine. The use of these drugs increased, and some patients found that their symptoms, and thyroid blood levels, were better controlled on natural desiccated thyroid, as compared to levothyroxine, or even levothyroxine with the addition of a synthetic form of T3 (the brand is Cytomel, generically it's known as liothyronine.)
As more patients asked for natural desiccated thyroid, and more practitioners -- particularly those with a more integrative or holistic focus -- prescribed it, the controversy grew. The conventional endocrinology world - despite a lack of research to back up their claims, declared that natural desiccated thyroid was old-fashioned, inconsistent, not stable, and did not work as well as levothyroxine. Some insisted to patients that it was already off the market, or it was soon going to be taken off the market. Misinformation abounded, with doctors -- and even prominent groups like Public Citizen -- erroneously claiming that natural desiccated thyroid drugs were available without a prescription, or were made from cows, and thus were a risk (due to prion diseases, i.e., "Mad Cow Disease.") Official treatment guidelines recommended levothyroxine, and discouraged use of natural desiccated thyroid drugs.
But still, as patient empowerment and knowledge increased, and as holistic and alternative medicine gained a greater foothold, the number of prescriptions for natural thyroid drugs increased. A lab, Western Research, that had made natural desiccated thyroid drugs Nature-Throid and Westhroid, was purchased by RLC Labs, and these two drugs gained greater market share as well.
As a patient advocate, I've always said that the best thyroid hormone replacement drug is the one that safely works best for each patient, as determined by the doctor and his/her patient. But I also felt obligated to make patients aware that there were other options besides levothyroxine to treat their hypothyroidism, including the addition of T3, and use of natural desiccated thyroid drugs. This did not sit well with the conventional endocrinology world, who continued to rail against natural desiccated thyroid drugs. One especially vehement endocrinologist, Richard Guttler, MD, who has been a vocal opponent of patients receiving anything besides levothyroxine, erroneously said years ago that natural thyroid would soon be off the market, and even wrote to me saying "...next it will be natural designer organic bathtub thyroid personally brewed at your web site." Clearly, hostility toward natural desiccated thyroid - and to patient advocates who make other patients aware of its existence -- runs deep.
As recently as late 2012, the Clinical Practice Guidelines for Hypothyroidism in Adults -- published by the American Association of Clinical Endocrinologists (AACE) and the American Thyroid Association (ATA) -- misrepresented natural desiccated thyroid. I summarized the concerns with the Guideline's discussion of natural thyroid in this editorial, but basically, they continued to suggest that there were prescription drugs of bovine (cow) origin -- there aren't -- and tried to close the subject by saying "There is no evidence to support using desiccated thyroid hormone in preference to L-thyroxine monotherapy in the treatment of hypothyroidism and therefore desiccated thyroid hormone should not be used for the treatment of hypothyroidism." What they failed to mention? There is no evidence to support using levothyroxine in preference to natural desiccated thyroid. The research simply hadn't been done either way, so years of habit, dogma, and marketing -- not double-bind, peer-reviewed, journal-published studies -- were the driving forces behind their recommendations.
But behind the scenes, practitioners continue to prescribe natural desiccated thyroid, patients continued to ask for it and take it, and positive news came out in late 2012, when the U.S. National Institutes of Health announced a clinical trial to study natural desiccated thyroid drugs versus levothyroxine, for the treatment of primary hypothyroidism.
Now, at the Endocrine Society Annual Meeting, which took place June 15 through 18, 2013 in San Francisco, Dr. Thanh Hoang, a staff endocrinologist at the Walter Reed National Military Medical Center in Bethesda, MD, presented results of his research on natural desiccated thyroid drugs.
Dr. Hoang's randomized, double blind, crossover study compared natural desiccated thyroid to levothyroxine. The study evaluated 70 patients (ages 18 to 65) who had primary hypothyroidism. The patients were randomly assigned to either natural desiccated thyroid or levothyroxine for 16 weeks. The studies were blind, meaning that patients did not know which medication they were receiving.
At the conclusion of the study, patients were asked which regimen they preferred, and almost 49% preferred the natural desiccated thyroid, versus almost 19% who preferred levothyroxine. About 33% didn't specify a preference. Dr. Hoang also reported that the patients taking natural desiccated thyroid lost approximately three pounds, compared to the patients taking levothyroxine, who did not lose weight.
Dr. Hoang told Endocrine Today, "We didn't find any differences in the neurocognitive measurements between the two therapies...We now know that once-daily desiccated thyroid extract is a safe alternative treatment for patients with hypothyroidism who are not satisfied with levothyroxine treatment. It's an option for them to try, and also desiccated can cause modest weight loss in these patients as well."
Dr. Hoang's research, and his presentation of that research to the Endocrine Society, is a major step, and an important one, for thyroid patients. Patients have the right to be prescribed -- and practitioners have the right to prescribe -- whichever brand or type of thyroid hormone replacement medication works safely and best for each patient. Dr. Hoang's willingness to challenge the conventional thyroid dogma, should be commended, and I look forward to larger studies and research findings comparing natural desiccated thyroid to levothyroxine in the future.