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T4+T3 Combination Therapy: An Unsolved Problem of Increasing Magnitude and Complexity.

Wilmar M Wiersinga1

  • 1Department of Endocrinology, Amsterdam University Medical Center, Academic Medical Center, Amsterdam, the Netherlands.

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|September 30, 2021
PubMed
Summary
This summary is machine-generated.

Thyroid hormone replacement with levothyroxine (LT4) may not resolve all hypothyroid symptoms. Combination therapy with thyroxine (T4) and triiodothyronine (T3) is an option for persistent issues, but other causes should be explored.

Keywords:
HypothyroidsmManagementPathophysiologyPersistent symptomsPrevalenceT4 monotherapyT4+T3 combination therapy

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Area of Science:

  • Endocrinology
  • Pharmacology
  • Internal Medicine

Background:

  • Persistent symptoms in levothyroxine (LT4)-treated hypothyroid patients, despite normal thyroid-stimulating hormone, are common.
  • These symptoms include fatigue, weight management issues, memory, and mood disturbances, affecting a significant portion of patients.
  • Potential causes range from unrealistic expectations and comorbidities to low tissue triiodothyronine (T3) levels.

Purpose of the Study:

  • To evaluate the role and growing popularity of combination therapy with thyroxine (T4) and triiodothyronine (T3) for hypothyroid patients with persistent symptoms.
  • To discuss the potential pathophysiological explanations for persistent symptoms and the evidence supporting T4+T3 therapy versus alternative causes.
  • To emphasize the need for further research and improved patient-physician communication in managing treatment dissatisfaction.

Main Methods:

  • Review of current literature and clinical practices regarding T4+T3 combination therapy for hypothyroidism.
  • Analysis of reported prevalence and types of persistent symptoms in LT4-treated patients.
  • Discussion of proposed pathophysiological mechanisms, including low tissue T3 and other contributing factors.

Main Results:

  • Combination T4+T3 therapy is increasingly used, particularly in high-income countries, for persistent hypothyroid symptoms.
  • High prevalence of symptoms like fatigue, weight issues, and cognitive difficulties is reported.
  • Circumstantial evidence suggests T4+T3 may normalize brain T3 levels, unlike T4 alone, but other causes are often considered more relevant.

Conclusions:

  • While T4+T3 combination therapy is an option for persistent hypothyroid symptoms, its efficacy requires more robust clinical validation.
  • Alternative causes for persistent symptoms must be thoroughly investigated and addressed.
  • Enhancing doctor-patient communication and managing expectations are crucial for optimizing hypothyroidism treatment outcomes, especially concerning subclinical cases where LT4 efficacy is limited.