Treatment Options for Hypothyroidism
Natural desiccated thyroid (NDT) and levothyroxine are two different types of medications used in the treatment of hypothyroidism, a condition where the thyroid gland does not produce enough thyroid hormones. Here are the key differences between the two:
Composition:
NDT: derived from animal thyroid glands. It contains a combination of both T4 (thyroxine) and T3 (triiodothyronine) hormones.
Levothyroxine: Levothyroxine is a synthetic form of the T4 hormone alone. It is the most commonly prescribed medication for hypothyroidism.
Inactive T4 to Active T3 Conversion:
NDT: Provides both T4 and the active T3 hormone directly, potentially bypassing the need for the body to convert T4 to T3.
Levothyroxine: The body needs to convert the T4 in levothyroxine to T3 for it to be biologically active. Some research suggests individuals may have difficulty with this conversion process depending on genetic differences (2017 study).[1]
Studies Comparing Desiccated Thyroid and Levothyroxine
Our clinic completed a search for all studies comparing NDT and levothyroxine from 1980 to January 2024. We found four studies that have been published in the world’s largest medical database (Pubmed) and one additional study from outside of this database (from the Journal of the Endocrine Society). Most of these studies are recent and are from large reputable peer-reviewed journals (with the exception of the 2023 study on 13 patients below).
A 2021 study enrolled 75 patients and compared desiccated thyroid to levothyroxine and found:[2]
The 1/3 most symptomatic patients on levothyroxine revealed strong preference for treatment containing T3 (desiccated thyroid or liothyronine), which improved performance on TSQ-36, GHQ-12, BDI, and visual memory index (VMS-IV component)
A small trend towards greater improvement LDL and HDL cholesterol levels
A higher level of activated thyroid hormone (free T3), with a lower level of inactive thyroid hormone (free T4)
A small trend towards lower thyroid-symptoms (As measured by TSQ-36)
Another 2021 study study enrolled 75 patients and compared desiccated thyroid, synthetic T3 + T4 combination, and levothyroxine and found:
More patients with Hashimoto’s preferred desiccated thyroid and T4/T3 combination than levothyroxine.[3]
As a group as a whole, there was no significant difference between the 3 treatment groups with regards to thyroid symptom questionnaire or other outcomes
A 2013 study enrolled 70 patients compared desiccated thyroid to levothyroxine and found:[4]
Those on desiccated thyroid lost an average of one additional pound of weight per month than those on levothyroxine
A 2021 study enrolled 31 patients and found that after patients switched from levothyroxine to desiccated thyroid symptoms related to hypothyroidism decreased in half.[5]
A 2023 study compared results of 13 patients who switched from desiccated thyroid and found that patients who had hypothyroid symptoms despite use of desiccated thyroid had an improvement on liquid levothyroxine.[6] Data has found that liquid versions of levothyroxine appear to be much better absorbed in that they do not interact with food as much (2022 study).[7] Given the size of the study however, it is difficult to draw conclusions.
Is Natural Desiccated Thyroid or Levothyroxine Better?
There is likely not enough evidence to claim one treatment is better than the other. Furthermore, the results vary for each person. Some people find levothyroxine works well and others find NDT works well. Studies suggest that if a person finds levothyroxine is working well, then stick with it (2020[8], 2021[9]). Otherwise for patients that are still symptomatic on levothyroxine, NDT may be preferred as these individuals tend to find greater symptom improvement.
Are Doses of Desiccated Thyroid Standardized?
It is sometimes argued that levothyroxine is highly standardized and consistent in its T4 content and desiccated thyroid is more variable in the amount of T4 and T3. Consequently, if T4 and T3 concentrations are inconsistent then this could lead to volatile thyroid levels in the body. However, a 2020 study found that desiccate thyroid kept the most commonly assessed thyroid marker, TSH, within the normal range 79.3% of the time, compared to 79.1% of the time with levothyroxine.[10]
Concluding Remarks
The largest studies from above that were from higher impact journals found desiccated thyroid hormone is equivalent to levothyroxine with regards to symptoms, and may provide greater benefits in some individuals (those with Hashimoto’s or who have had limited improvements on levothyroxine). A number of studies have found that desiccated thyroid appears to lead to a higher level of activated thyroid hormone (free T3) and may cause greater weight loss and improvement in overall symptoms in certain individuals. You can connect with one of our naturopaths here if you have more questions or wish to pursue desiccated thyroid.
References
[1] A Step Forward in Understanding the Relevance of Genetic Variation in Type 2 Deiodinase
Marco Medici, Layal Chaker, Robin P. Peeters Author Notes The Journal of Clinical Endocrinology & Metabolism, Volume 102, Issue 5, 1 May 2017, Pages 1775–1778, https://doi.org/10.1210/jc.2017-00585
[2] Shakir MKM, Brooks DI, McAninch EA, Fonseca TL, Mai VQ, Bianco AC, Hoang TD. Comparative Effectiveness of Levothyroxine, Desiccated Thyroid Extract, and Levothyroxine+Liothyronine in Hypothyroidism. J Clin Endocrinol Metab. 2021 Oct 21;106(11):e4400-e4413. doi: 10.1210/clinem/dgab478. PMID: 34185829; PMCID: PMC8530721.
[3] Desiccated Thyroid Extract Versus Synthetic LT4/T3 Combination Versus LT4 Monotherapy in the Treatment of Primary Hypothyroidism With Special Attention to the Thr92AlaD2 Polymorphism. With Special Attention to the Gene Polymorphism Thanh Duc Hoang, DO, Daniel I Brooks, PhD, Antonio Bianco, MD, Elizabeth A Mcaninch, MD, Tatiana L Fonseca, PhD, Vinh Q Mai, DO, Mohamed K M Shakir, MD Journal of the Endocrine Society, Volume 5, Issue Supplement_1, April-May 2021, Pages A827–A828, https://doi.org/10.1210/jendso/bvab048.1687 Published: 03 May 2021
[4] Desiccated Thyroid Extract Compared With Levothyroxine in the Treatment of Hypothyroidism: A Randomized, Double-Blind, Crossover Study Thanh D. Hoang, Cara H. Olsen, Vinh Q. Mai, Patrick W. Clyde, Mohamed K. M. Shakir The Journal of Clinical Endocrinology & Metabolism, Volume 98, Issue 5, 1 May 2013, Pages 1982–1990, https://doi.org/10.1210/jc.2012-4107
[5] Heald AH, Premawardhana L, Taylor P, Okosieme O, Bangi T, Devine H, Livingston M, Javed A, Moreno GYC, Watt T, Stedman M, Dayan C, Hughes DA. Is there a role for natural desiccated thyroid in the treatment of levothyroxine unresponsive hypothyroidism? Results from a consecutive case series. Int J Clin Pract. 2021 Dec;75(12):e14967. doi: 10.1111/ijcp.14967. Epub 2021 Nov 20. PMID: 34626513.
[6] Khoshaba L, Patarkatsi L. Switching from Natural Desiccated Thyroid to a Liquid Formulation of Levothyroxine for Hypothyroidism. Case Rep Endocrinol. 2023 Dec 28;2023:4252894. doi: 10.1155/2023/4252894. PMID: 38179415; PMCID: PMC10766474.
[7] Ducharme M, Scarsi C, Bettazzi E, Mautone G, Lewis Y, Celi FS. A Novel Levothyroxine Solution Results in Similar Bioavailability Whether Taken 30 or Just 15 Minutes Before a High-Fat High-Calorie Meal. Thyroid. 2022 Aug;32(8):897-904. doi: 10.1089/thy.2021.0604. Epub 2022 May 23. PMID: 35469428; PMCID: PMC9419984.
[8] Liothyronine and Desiccated Thyroid Extract in the Treatment of Hypothyroidism. Thaer Idrees, Scott Palmer, Rui M.B. Maciel, and Antonio C. Bianco. Published Online:16 Oct 2020 https://doi.org/10.1089/thy.2020.0153
[9] Comparative Effectiveness of Levothyroxine, Desiccated Thyroid Extract, and Levothyroxine+Liothyronine in Hypothyroidism
Mohamed K M Shakir, Daniel I Brooks, Elizabeth A McAninch, Tatiana L Fonseca, Vinh Q Mai, Antonio C Bianco, Thanh D Hoang
The Journal of Clinical Endocrinology & Metabolism, Volume 106, Issue 11, November 2021, Pages e4400–e4413, https://doi.org/10.1210/clinem/dgab478
[10] Kuye R, Riggs C, King J, Heilmann R, Kurz D, Milchak J. Thyroid Stimulating Hormone Stability in Patients Prescribed Synthetic or Desiccated Thyroid Products: A Retrospective Study. Ann Fam Med. 2020 Sep;18(5):452-454. doi: 10.1370/afm.2545. PMID: 32928762; PMCID: PMC7489980.