Use of the 36-Point Thyroid Symptom Questionnaire to Potentially Guide Optimal Thyroid Hormone Replacement Therapy

Area of Science:

• Endocrinology
• Thyroidology
• Pharmacology

Background:

• Levothyroxine (LT4) is the standard treatment for hypothyroidism.
• Some patients experience persistent symptoms despite normalized thyroid stimulating hormone (TSH) levels on LT4 therapy.
• This may indicate a need for alternative or adjunctive thyroid hormone formulations.

Purpose of the Study:

• To assess the impact of switching from LT4 to combination therapy (levothyroxine + liothyronine [LT4+LT3]) or desiccated thyroid extract (DTE) on patient-reported symptoms.
• To determine if baseline symptom severity on LT4 influences treatment preference and outcomes.

Main Methods:

• A post hoc subgroup analysis of 143 patients from two randomized, double-blind, crossover studies was conducted.
• Patients were stratified into Low, Moderate, and High Symptom groups based on their Thyroid Symptom Questionnaire (TSQ-36) scores while on LT4.
• Symptom scores (TSQ-36) were compared across LT4, LT4+LT3, and DTE treatments at normal TSH levels.

Main Results:

• Patients with moderate-to-severe symptoms on LT4 reported significantly lower symptom scores on DTE and, in some cases, LT4+LT3 compared to LT4.
• Patients with low symptoms on LT4 experienced lower symptom scores on LT4 compared to DTE and LT4+LT3.
• Therapy preference correlated with symptom severity, with those preferring combination therapy having higher baseline symptom scores.

Conclusions:

• The Thyroid Symptom Questionnaire (TSQ-36) can quantify symptoms and guide thyroid hormone therapy selection.
• Patients with persistent moderate-to-severe symptoms on LT4 may benefit from a trial of combination therapy or DTE.
• Individuals with mild symptoms on LT4 should generally continue LT4 monotherapy.