This is a well-designed, double-blind, crossover trial putting DTE and levothyroxine head-to-head. The top line findings, that the primary outcomes for the whole group weren’t different, is a great start for substantiating that at the least Natural Desiccated Thyroid is equivalent to levothyroxine.

However the secondary findings, although in a sub-group population are very intriguing and underline what we commonly see in clinical practice. Patients lost an average of nearly 3 pounds on DTE and nearly 50% of patients preferred DTE!  Even though the subgroup analysis needs to be interpreted with caution, it strongly suggests that for a certain subset of patients, likely those that don’t convert the synthetic T4 over to the more active T3 form, DTE may offer real, subjective benefits in symptoms and well-being that L-T4 monotherapy just doesn’t provide.

🩺 Clinical Bottom Line

This small but well-designed, double-blind, crossover trial found that desiccated thyroid extract (DTE) was not superior to levothyroxine (L-T4) for improving hypothyroid symptoms or neurocognitive function in the overall study group. However, DTE treatment did result in a modest but statistically significant average weight loss of approximately 3 pounds compared to L-T4. The most notable finding was that nearly half (48.6%) of the patients preferred DTE over L-T4, compared to only 18.6% who preferred L-T4. While a subgroup analysis of the DTE-preferring patients did show significant symptom improvement, this finding should be viewed with extreme caution as it is a post-hoc analysis highly susceptible to bias.

📊 Results in Context

• Primary Outcome: The study’s primary outcome measures included symptom scores (Thyroid Symptom Questionnaire [TSQ]), general well-being (General Health Questionnaire [GHQ]-12), and a battery of neurocognitive tests.

  • Across all 70 participants, there were no statistically significant differences in hypothyroid symptoms, quality of life, or neurocognitive measurements between the DTE and L-T4 treatment periods.

• Key Secondary & Patient-Reported Outcomes (PROs):

  • Patient Preference: This was the study’s most significant finding. When asked at the end of the trial, 34 patients (48.6%) preferred DTE, 13 (18.6%) preferred L-T4, and 23 (32.9%) had no preference. The preference for DTE was statistically significant.

  • Weight Loss: Patients weighed, on average, 2.86 pounds less while on DTE therapy compared to L-T4 therapy (172.9 lbs vs. 175.7 lbs; P < .001).

  • Biochemical Profile: To maintain the target TSH (0.5-3.0 µIU/mL), the two therapies resulted in different biochemical profiles. During DTE treatment, serum total T3 was significantly higher and serum free T4 was significantly lower than during L-T4 treatment. Serum TSH was also slightly, but significantly, higher in the DTE group (1.67 vs. 1.30 µIU/mL).

  • PROs (Subgroup): In the subgroup of 34 patients who stated a preference for DTE, they showed significant improvements in subjective symptoms on both the TSQ and GHQ-12 questionnaires while taking DTE (P < .001 for both).

• Harms and Adverse Events:

  • No adverse effects were reported with either treatment.

  • All patients tolerated both DTE and L-T4 equally well. There were no significant changes in heart rate or blood pressure between the two groups.

🧐 Assertive Critical Appraisal

• Risk of Bias (RoB 2 Framework):

  • Overall judgment: Some concerns.

  • Critique: The randomized, double-blind, crossover design is a significant strength, as patients serve as their own controls, minimizing confounding. Randomization and allocation concealment appear robust.

  • The primary concern arises from the interpretation of the results. The study’s pre-specified primary outcomes (symptoms and neurocognition in the full group) were negative. The positive findings for symptom improvement were only identified in a subgroup analysis conducted after unblinding and assessing patient preference. This introduces a major risk of bias, as the subgroup is defined by the very outcome (preference) it seeks to explain.

• Subgroup Analyses:

  • The study’s most-discussed finding—that some patients “do better” on DTE—is based entirely on a subgroup analysis of those who preferred DTE.

  • As per standard appraisal, subgroup claims are often unreliable. While this analysis was pre-specified, it is not a randomized comparison. It is plausible that the patients who felt better (for any number of reasons, including the modest weight loss) subsequently stated a preference, making this a circular finding. These results should be considered hypothesis-generating, not conclusive.

• Appraisal of Patient-Reported Outcomes (CONSORT-PRO):

  • The PROs (TSQ, GHQ-12, BDI) were appropriately pre-specified as primary outcome measures.

  • The dropout rate was low (10%), meaning missing PRO data was unlikely to have biased the main (negative) finding. The study’s conclusion that DTE offered no significant PRO benefit overall is sound.

• Reporting Quality Assessment (CONSORT):

  • The reporting quality is high. The paper includes a CONSORT flow diagram (Figure 1) detailing participant allocation and follow-up.

  • It also clearly describes the methods for randomization (computer-generated list) and allocation concealment (maintained by a physician not involved in the study), which strengthens confidence in the trial’s validity.

• Applicability:

  • The study population (patients with primary hypothyroidism on stable L-T4) is directly relevant to general clinical practice.

  • The findings do not support switching all patients to DTE. However, they do provide evidence that for a patient who is dissatisfied with L-T4 monotherapy, a trial of DTE is a reasonable consideration. It may offer a modest benefit in weight and subjective well-being for some, with no apparent short-term adverse effects.

📝 Study Details

• Research Objective:

  • To investigate the effectiveness of DTE compared with L-T4 on symptoms, cognitive function, and general well-being in hypothyroid patients.

• Study Design:

  • A randomized, double-blind, crossover study.

  • Participants were randomized to one of two sequences: (1) DTE for 16 weeks, then L-T4 for 16 weeks, or (2) L-T4 for 16 weeks, then DTE for 16 weeks.

  • A total of 85 patients were assessed for eligibility, 78 were randomized, and 70 completed both study periods.

• Setting and Participants:

  • Setting: A single tertiary care center (Walter Reed National Military Medical Center).

  • Participants: 70 patients (age 18-65) with primary hypothyroidism who had been on a stable dose of L-T4 for at least 6 months prior to enrollment.

  • Exclusion criteria included pregnancy, coronary artery disease, significant lung/renal/liver disease, active cancer, and use of medications known to interfere with thyroid hormone (e.g., amiodarone, proton pump inhibitors, iron).

📚 Bibliographic Data

• Title: Desiccated Thyroid Extract Compared With Levothyroxine in the Treatment of Hypothyroidism: A Randomized, Double-Blind, Crossover Study

• Authors: Thanh D. Hoang, Cara H. Olsen, Vinh Q. Mai, Patrick W. Clyde, and Mohamed K. M. Shakir

• Journal: The Journal of Clinical Endocrinology and Metabolism (J Clin Endocrinol Metab)

• Year: 2013

• DOI: 10.1210/jc.2012-4107