Desiccated thyroid is a dried extract of animal thyroid glands, sold for hypothyroidism for decades. It contains T4 and T3, and it has been used by patients who prefer it. The evidence for it is much thinner than for levothyroxine, and this article shows exactly how thin.
The randomized crossover trial
Hoang and colleagues randomized 70 adults with primary hypothyroidism, all on a stable levothyroxine dose for six months, to desiccated thyroid extract or levothyroxine for 16 weeks each, double-blind, with a switch at the midpoint. Symptoms and neurocognitive measures did not differ between the two. About half of participants said they preferred the extract, and a smaller group preferred levothyroxine.
Weight, which was reported only in a conference abstract
In the same trial, patients on the extract lost slightly more weight than those on levothyroxine. The difference was small, and it was reported in a conference abstract, so it should be read as a signal and not as a treatment effect.
The 2024 systematic review
Riis, Larsen and Bonnema reviewed the evidence through January 2024. The two randomized trials showed no difference in quality of life or symptom scores. Observational studies favored the extract on symptoms. The review found the evidence overall of moderate to very low quality, with inferior study designs and little data on long-term effects and side effects.
What the guidelines say
The 2014 ATA guideline found too little evidence to recommend extracts and noted only one randomized comparison. The NHS Specialist Pharmacy Service recommends levothyroxine and does not support routine use of desiccated extracts, and it advises shared decision-making when a patient asks for one.
What this does not say
- The trial had 70 people and was not designed to detect rare harm.
- The trial product was one extract. Other products may differ in hormone content.
- Preference in a trial is not evidence of a better clinical outcome.
How we use this
If you ask for desiccated thyroid, our physicians will explain what the trials show and what they do not, and they will check your blood tests and symptoms on the product you take.
We do not promise that the extract works better than levothyroxine; the honest answer is that the evidence does not show it.
Explore weight loss treatmentsSources
- 1.Hoang TD et al. Desiccated thyroid extract compared with levothyroxine in the treatment of hypothyroidism: a randomized, double-blind, crossover study. J Clin Endocrinol Metab 2013;98:1982-1990. JCEM
- 2.Riis KR, Larsen CB, Bonnema SJ. Potential risks and benefits of desiccated thyroid extract for the treatment of hypothyroidism: a systematic review. Thyroid 2024. Thyroid
- 3.Jonklaas J et al. Guidelines for the treatment of hypothyroidism: prepared by the American Thyroid Association task force. Thyroid 2014;24:1670-1751. Thyroid (ATA)
- 4.Review of clinical evidence on use of desiccated thyroid extract products. NHS Specialist Pharmacy Service