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Desiccated thyroid extract

desiccated thyroid extract, desiccated thyroid extract vs levothyroxine
Desiccated thyroid or thyroid extract refers to porcine or bovine thyroid glands, dried and powdered for therapeutic use Animal extract thyroid preparations were developed in the late 19th century, and are still in use today for the treatment of hypothyroidism This product is sometimes referred to as "natural thyroid", "natural thyroid hormones", "pork thyroid", thyroid USP, thyroid BP, or by the name of a commercial brand, such as "Armour Thyroid" or "Nature-Throid" & "Westhroid"

Desiccated thyroid has been described in the United States Pharmacopoeia for a century as the cleaned, dried, and powdered thyroid gland previously deprived of connective tissue and fat obtained from domesticated animals that are used for food by man USP XVI In the last few decades, pork alone is the usual source Before modern assays, the potency was specified only by iodine content "not less than 017% and not more than 023%", rather than hormonal content or activity

Brands include Armour, Naturethroid, and Thyroid All brands consist of desiccated porcine thyroid powder, differing only in binders and fillers They contain a mixture of thyroid hormones: T4 thyroxine & T3 triiodothyronine, in the proportions usually present in pig thyroids approximately 80% T4 and 20% T3


  • 1 Medical uses
  • 2 History
  • 3 References
  • 4 External links

Medical uses

The American Association of Clinical Endocrinologists and the Royal College of Physicians recommend against the use of thyroid extract for the treatment of hypothyroidism Concerns include the potential for adverse effects from superphysiological levels of T3 and the absence of long-term safety data from randomized clinical trials They recommend synthetic levothyroxine as the preferred treatment Some practitioners refuse to use desiccated thyroid and will try to steer their patients away from it

Arguments against desiccated thyroid include:

  1. Desiccated thyroid preparations have a greater variability from batch to batch than synthetic ones
  2. Desiccated thyroid has roughly a 4:1 ratio of thyroxine T4 to triiodothyronine T3 In humans, the ratio is 11:1
  3. A combination of various ratios of T4 and T3 may not provide benefits over T4 alone Some controlled trials have shown inconsistent benefits of various ratios of T4 and T3
  4. The use of desiccated thyroid is usually accompanied with the practice of dosing according to symptoms instead of dosing to achieve "ideal" lab results eg serum levels of TSH While there is debate as to what the ideal serum levels are, dosing according to symptoms often results in higher dosages Most endocrinologists are opposed to these higher dosages as there may be risks of hyperthyroidism and osteoporosis
  5. The preference for "natural" treatment seems to stem from philosophical belief as opposed to science


The earliest oral treatment for hypothyroidism consisted of thyroid extract George Redmayne Murray of the United Kingdom first described treatment of myxedema with thyroid extract in 1891, and published a description of long-term successful treatment 28 years of a patient with myxedema severe hypothyroidism in 1920 His treatment was quickly adopted in North America and Europe The first recorded American use dates to 1891 by a woman who was still taking it 52 years later at 84 years of age

Desiccated thyroid extract is prepared from pig thyroid glands The glands are dried desiccated, ground to powder, combined with binder chemicals, and pressed into pills This was a new use for parts that were previously unwanted slaughterhouse offal, and Armour and Company, the dominant American meatpacker in the 20th century, supplied the best-known brand of thyroid extract

Replacement by thyroid extract in hypothyroidism was one of the most effective treatments of any disease available to physicians before the middle of the 20th century, and in severe cases afforded dramatic relief of the myriad symptoms The decision to treat was usually based on the presence of signs and symptoms of hypothyroidism because there were no accurate, readily available laboratory tests of thyroid function Many less severe cases of hypothyroidism went untreated Dosage was regulated by improvement of symptoms

Desiccated Thyroid became a commercial treatment option in 1934 with Westhroid, In the early 1960s, desiccated thyroid hormones thyroid extract began to be replaced by levothyroxine T4, or by combinations of T4 and T3 Replacement occurred faster in the United Kingdom than in North America, but by the 1980s more patients were being prescribed levothyroxine or T4/T3 combinations than desiccated thyroid extract

Several reasons have been identified as to why prescriptions changed from desiccated thyroid treatment

  • Although thyroid extract was useful and usually effective, some patients continued to complain of fatigue, weight gain, or other symptoms Dosing until the 1960s was often a matter of prolonged adjustment trials
  • It was known that not all of the iodine content of thyroid extract was in the form of effective T4 and T3 and that actual content of available preparations varied more than the permitted 15% It was hoped that better dosing precision with levothyroxine alone would increase the proportion of patients effectively treated In 1980, a widely publicized investigation published in JAMA revealed continued large ranges of hormone content and potency in all of the available thyroid extracts on the American market
  • By the 1960s, it was known that thyroxine was the essential hormone produced by the thyroid gland, and that most T3 was manufactured in other parts of the body by deiodination of thyroxine It was demonstrated in hypothyroid animals and people that replacement of thyroxine alone corrected the measurable manifestations laboratory test results of hypothyroidism By the 1970s doctors could measure T4, T3, and TSH in human blood with approximate accuracy and confirmed that treatment with thyroxine alone could produce normal blood levels of both T4 and T3, but desiccated thyroid caused supraphysiologic levels of T3 In the majority of patients normalization of these levels eliminated all signs and symptoms of hypothyroidism
  • It was discovered that a healthy person varied the amount of T3 produced from T4 in response to changing needs and conditions and it seemed wiser not to bypass this control system by providing larger amounts of T3 than were naturally produced each day
  • Furthermore, when T3 could be measured, it was discovered that thyroid extract and synthetic combinations of T4 and T3 produced significantly greater fluctuations of T3 throughout the day than occurred in healthy people or hypothyroid people treated with thyroxine alone
  • Endocrinologists found that treatment with thyroxine alone worked as well or better than thyroid extract for the majority of patients, although even thyroxine did not reverse all the symptoms of a minority

Thyroid care changed in other ways as well Accurate T4 and T3 measurements became widely used in the 1970s, and by the late 1980s, TSH measurement had become sensitive enough to detect mild degrees of hyperthyroidism and overtreatment Blood levels of thyroid hormones and TSH were found to be the best predictors of objective benefits from thyroid replacement: those with the most severe measurable deficiency enjoyed the most dramatic and sustained benefits It was also discovered that even mild hyperthyroidism as defined by a suppressed TSH level, whether due to disease or overtreatment, was associated with poorer bone density in women, and with higher rates of atrial fibrillation in elderly patients


  1. ^ Professional Guide to Drugs- A Reference for Doctors, Nurses, Dentists, Pharmacists- Anyone Who Prescribes, Administers, or Takes Medicines Cal State Long Beach Library: Intermed Communications Books 1982 p 592 ISBN 0916730514 
  2. ^ "Thyroid, Oral Version 2012, Issue 1" RelayClinical Education February 2012 
  3. ^ US Pharmacopeia Natural Formulary USP 37 N32 2014 Volume 3 May 1, 2014 The United States Pharmacopeial Convention 2014 ISBN 9781936424221 
  4. ^ Tory, David B 2006 Remington The Science and Practice of Pharmacy, 21st edition Philadelphia, PA: Lippincott Williams and Wilkins pp 1460, 1461 ISBN 0781763789 
  5. ^ 2008 AHFS Drug Information Bethesda, MD: American Society of Health-Systems Pharmacists 2008 pp 3308, 3309 ISBN 978-1-58528206-7 
  6. ^ Garber, JR; Cobin, RH; Gharib, H; Hennessey, JV; Klein, I; Mechanick, JI; Pessah-Pollack, R; Singer, PA; Woeber, KA for the American Association of Clinical Endocrinologists and the American Thyroid Association Taskforce on Hypothyroidism in Adults December 2012 "Clinical Practice Guidelines for Hypothyroidism in Adults" PDF Thyroid 22 12: 1200–1235 doi:101089/thy20120205 PMID 22954017 
  7. ^ "Thyroid disorders 'misdiagnosed'" BBC News 2009-03-27 Retrieved 2009-03-30 the only accurate way to diagnose a thyroid disorder is via a blood test which measures hormone levels, and the only scientifically proven way of treating the condition is by topping up a patient's natural thyroxine levels with a synthetic form of the hormone 
  8. ^ a b "Endocrine Today Blog" Endocrinetodaycom Retrieved 2014-07-24 
  9. ^ Repas, Thomas Desiccated thyroid in the management of hypothyroidism: Part I
  10. ^ Baskin, HJ; Cobin, RH; Duick, DS; Gharib, H; Guttler, RB; Kaplan, MM; Segal, RL; American Association of Clinical, Endocrinologists 2002 "American Association of Clinical Endocrinologists medical guidelines for clinical practice for the evaluation and treatment of hyperthyroidism and hypothyroidism" PDF Endocrine Practice 8 6: 457–69 PMID 15260011 
  11. ^ Clyde, PW; Harari, AE; Getka, EJ; Shakir, KM 10 December 2003 "Combined levothyroxine plus liothyronine compared with levothyroxine alone in primary hypothyroidism: a randomized controlled trial" JAMA 290 22: 2952–8 doi:101001/jama290222952 PMID 14665656 
  12. ^ "Endocrine Today Blog" Endocrinetodaycom Retrieved 2014-07-24 
  13. ^ "Endocrine Today Blog" Endocrinetodaycom Retrieved 2014-07-24 
  14. ^ Murray GR The life history of the first case of myxoedema treated by thyroid extract Br Med J 1920;i:359-60
  15. ^ Burgess AM Myxedema-- controlled by thyroid extract for fifty-two years: report of a case Ann Internal Med 1946; 25:146
  16. ^ Means JH, DeGroot LJ, Stanbury JB The Thyroid and its Diseases 3rd ed New York:McGraw Hill, 1963 See chapter 9 for a lengthy discussion of the difficulties of assessing treatment in the era before effective tests, as well as the doctors' impressions of the superiority of the new synthetic thyroxine that had just become available
  17. ^ Macgregor AG February 1961 "Why does anybody use thyroid BP" Lancet 1 7172: 329–32 doi:101016/s0140-67366191498-2 PMID 13764789 
  18. ^ Catz B, Ginsburg E, Salenger S 1962 "Clinically inactive thyroid USP: a preliminary report" N Engl J Med 266: 136 doi:101056/nejm196201182660308 
  19. ^ Pileggi VJ, Golub DJ, Lee ND 1965 "Determination of thyroxine and triiodothyronine in commercial preparations of desiccated thyroid and thyroid extract" J Clin Endocrinol Metab 25: 949–56 doi:101210/jcem-25-7-949 
  20. ^ Mangieri CN, Lund MH January 1970 "Potency of United States Pharmacopeia desiccated thyroid tablets as determined by the antigoitrogenic assay in rats" J Clin Endocrinol Metab 30 1: 102–4 doi:101210/jcem-30-1-102 PMID 5409525 
  21. ^ Rees-Jones RW, Rolla AR, Larsen PR February 1980 "Hormonal content of thyroid replacement preparations" JAMA 243 6: 549–50 doi:101001/jama198003300320041023 PMID 7351788 
  22. ^ Braverman LE, Ingbar SH, Sterling K Conversion of thyroxine to triiodothyronine in athyreotic human subjects J Clin Invest 1970; 49:855-64
  23. ^ Saberi M, Utiger RD Serum thyroid hormone and thyrotropin concentrations during thyroxine and triiodothyronine therapy J Clin Endocrinol Metab 1974; 39:923-7
  24. ^ Penny R, Frasier SD January 1980 "Elevated serum concentrations of triiodothyronine in hypothyroid patients Values for patients receiving USP thyroid" American Journal of Diseases of Children 134 1: 16–8 doi:101001/archpedi198002130130008003 PMID 7350782 
  25. ^ a b Capiferri R, Evered D March 1979 "Investigation and treatment of hypothyroidism" Clin Endocrinol Metab 8 1: 39–48 doi:101016/S0300-595X7980008-0 PMID 371874 
  26. ^ Surks MI, Schadlow AR, Oppenheimer JH A new radioimmunoassay for L-triiodothyronine: measurement in thyroid disease and in patients maintained on hormonal replacement J Clin Invest 1972; 51:3104-13

External links

  • Allergan Armour Thyroid insert PDF

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