Made from dried and powdered pig thyroid glands, the thyroid extract medications Armour, NP Thyroid, Nature-Thyroid and WP Thyroid seem to be making a comeback. In a recent American Thyroid Association survey of more than 12,000 people with hypothyroidism, early results released this spring showed that about 30% reportedly took natural or compounded thyroid medications. During the 2016 presidential election, a thyroid extract made national headlines when Hillary Clinton’s medical report showed she was taking Armour for a low-thyroid condition. 1
Once the mainstay of hypothyroid treatment, thyroid extracts fell out of use in the 1970s with the rise of synthetic levothyroxine. 2 While levothyroxine is used by most people with hypothyroidism—and one of America’s top-selling drugs—there’s growing interest in thyroid extracts among people whose low-thyroid symptoms don’t seem to lift with levothyroxine alone. And lately, there’s been cautious interest among doctors and researchers, too.
Also called desiccated thyroid extract, these drugs are prescription-only. They’re not recommended for older adults. Government health groups consider desiccated thyroid extracts “high risk” for people age 65+ and Medicare doesn’t cover them due to higher risk for dangerous, off-beat heart rhythms in older people who may have heart problems.3
Animal thyroid extracts were first used to treat hypothyroidism in the Western world in the early 1890s. And there’s evidence Chinese healers had been recommending them for far longer – sometimes mixed with fruit so they tasted better.4 Up through the 1960s, 80% of thyroid prescriptions written in the U.S. were for natural extracts.4 But at the time, levels of hormones in extracts were not consistent. Some had twice as much as the label said, some had none at all. And the tablets didn’t have a very long shelf life.
When synthetic levothyroxine took off in the 1970s, doctors saw extracts as a thing of the past – and wrote medical-journal articles with titles like “Why does anyone still use desiccated thyroid” and “Desiccated thyroid preparations -- obsolete therapy.”
Today, levels of the thyroid hormones T3 and T4 are standardized in desiccated thyroid extracts. And doctors and researchers are paying attention to people who say they feel better on these drugs. For some people with hypothyroidism, synthetic T4 doesn’t seem to get converted into T3 – the form cells throughout your body and brain use. The experience of people who take thyroid extract has provided a research clue for researchers trying to understand what’s going on.
Unlike synthetic levothyroxine – the thyroid hormone T4, which the body normally converts to an active and more potent form called T3 – desiccated thyroid extracts contain T4 plus T3 as well as small amounts of thyroid co-factors T1, T2, calcitonin and iodine. Some proponents say this suite of ingredients is more “natural.” Others say they just feel better taking it.
In one of the only studies comparing desiccated thyroid extract to levothyroxine, doctors from Walter Reed National Military Medical Center in Bethesda, MD, compared the results when 70 people with hypothyroidism took each medication for 16 weeks. Afterward, 49% said they preferred the extract, 18% preferred levothyroxine and 33% had no preference. “Patients who preferred DTE [desiccated thyroid extract] lost approximately 4 pounds …compared with L-T4 treatment. In addition, their general well-being and thyroid symptoms were significantly better,” the researchers report.
And in a 2014 study5 in the Journal of Endocrinology, Diabetes & Obesity of 154 women and men who didn’t feel better while taking levothyroxine, 78% who switched to a thyroid extract said they preferred it. Side effects were minor.
But medical groups like the American Thyroid Association and the American Association of Clinical Endocrinologists warn that long-term studies are needed.
“Although there is preliminary evidence from a short-duration study that some patients may prefer treatment using thyroid extracts, high-quality controlled long-term outcome data are lacking to document superiority of this treatment compared to levothyroxine therapy,” the ATA notes in its most recent treatment guidelines6 for people with hypothyroidism. And in its 2012 joint guidelines7 with the ATA, the AACE voiced a similar opinion: “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…”
One concern: Thyroid extracts have three and a half times more T3 in relation to T4 compared to the ratio produced by a healthy human thyroid gland. That could lead to too-high T3 levels, which might affect heart health, bone density and cause symptoms normally found in people with an overactive thyroid, the American Thyroid Association warns. The ATA cites one study that found “a larger number of hyperthyroid symptoms when individuals were taking desiccated thyroid preparations compared with levothyroxine preparations, which was attributed to T3 effects.” And when researchers from the University of Minnesota asked endocrinologists around the country about adverse events in their patients taking desiccated thyroid extracts for a 2017 study8, they got 174 reports. Sixty-five percent seemed related to too-high levels of thyroid hormones, including weight loss, nervousness, trouble sleeping, heart palpitations and two cases of off-beat heart rhythms. “The majority of clinical symptoms reported were consistent with being the consequence of an excess of thyroid hormone action,” the researchers note.
Endocrinologist Beatriz Olson, MD, FACP, Associate Faculty and Assistant Clinical Professor of Medicine at the Yale University School of Medicine, said she will sometimes prescribe a combination of levothyroxine and thyroid extract to patients who want to take a natural thyroid extract. “This brings the ratio of T4 to T3 more in line with normal human levels,” she explains.
1. Letter from Hillary Clinton’s physician Lisa Bardack, MD, Chair of Internal Medicine at CareMount Medical, September 14, 2016, updating Hillary Clinton’s health. https://www.washingtonpost.com/news/the-fix/wp/2016/09/14/hillary-clintons-new-doctors-letter-annotated/?utm_term=.fd9626e12572
2. Hypothyroidism and Thyroid Substitution: Historical Aspects. J Lindholm. Journal of Thyroid Research. Volume 2011 (2011)
4.. “Alternatives for High-Risk Medications in the Elderly.” Simply Healthcare. URL: http://www.simplyhealthcareplans.com/sites/default/files/High%20Risk%20Drug%20Guide_Jan2014%20%282%29_0.pdf
5. “The discovery of thyroid replacement therapy. Part 1: In the beginning.” Slater S. Journal of the Royal Society of Medicine, 2011: 104: 15–18. URL: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3014555/
6. “The History and Future of Treatment of Hypothyroidism.” McAninch EA and Bianco AC. Ann Intern Med. 2016 January 5; 164(1): 50–56. URL: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4980994/
7. “Conversion to Armour Thyroid from Levothyroxine Improved Patient Satisfaction in the Treatment of Hypothyroidism.” Pepper GM et al. J Endocrinol Diabetes Obes 2(3): 1055. URL: http://jeffreydachmd.com/wp-content/uploads/2013/06/Conversion-to-Armour-Thyroid_endocrinology-2-1055.pdf
8. “Guidelines for the Treatment of Hypothyroidism Prepared by the American Thyroid Association Task Force on Thyroid Hormone Replacement.” Jonklaas J et al. Thyroid. Volume 24, Number 12, 2014
9. “Clinical practice guidelines for hypothyroidism in adults: cosponsored by the American Association of Clinical Endocrinologists and the American Thyroid Association.” Garber JR et al. Endocrine Practice. 2012 Nov-Dec;18(6):988-1028.
10. “Adverse event reporting in patients treated with thyroid hormone extract.” Shrestha RT et al. Endocr Pract. 2017 May;23(5):566-575. URL: https://www.ncbi.nlm.nih.gov/pubmed/28225316