# Correlation of Residual Symptoms With Triiodothyronine (T3) in Patients Treated for Hypothyroidism

## TL;DR

This study finds that residual symptoms in hypothyroid patients on levothyroxine are linked to lower triiodothyronine (T3) levels, suggesting T3 may influence mental and physical well-being.

## Contribution

The study introduces the thyroid symptom questionnaire (TSQ) as a potential tool to identify patients with residual hypothyroid symptoms linked to T3 levels.

## Key findings

- 75.9% of euthyroid hypothyroid patients reported at least one residual symptom.
- Lower T3 levels were significantly correlated with higher scores on mental health and symptom questionnaires.
- Dry skin and weight gain were the most commonly reported residual symptoms.

## Abstract

Background

Despite the time-honored concept that a normal serum thyroid-stimulating hormone (TSH) indicates that there is euthyroidism in all tissues, there is accumulating evidence questioning this notion. This could explain why a subset of patients remain symptomatic despite treatment with levothyroxine. This study will help identify patients with residual symptoms through questionnaires and the relation of the test scores (obtained from these questionnaires) to serum triiodothyronine (T3) levels.

Methods

A total of 108 hypothyroid patients on levothyroxine supplementation who are biochemically euthyroid were included. Residual symptoms on treatment and symptom questionnaires (thyroid symptom questionnaire (TSQ), general health questionnaire (GHQ-12), Hospital Anxiety and Depression Scale (HADS) and Epworth Sleepiness Score (ESS)) were administered to subjects and their scores correlated with T3 values.

Results

A total of 108 subjects, comprising 98 females (90.7%) and 10 males (9.3%), with a mean age of 39.19 years (± 13.18 years), were analyzed in this study. The majority of the participants (75.9%, n=82) reported experiencing at least one symptom. The most prevalent symptom was dry skin, reported by 44.4% (n=48) of the subjects, followed by weight gain, which affected 30.6% (n=33) of the participants. Statistical analysis revealed significant inverse correlations between all assessed scores - TSQ, GHQ-12, HADS, and ESS - with T3 values. The correlation coefficients and corresponding p-values indicate significant relationships between thyroid function and psychological well-being in the studied population. The following correlation coefficients (r values) were obtained: TSQ, r=-0.331 (p = 0.001); GHQ-12, r=-0.292 (p = 0.002); HADS-A, r=-0.318 (p = 0.001); HADS-D, r = -0.233 (p = 0.015); and the ESS, r=-0.205 (p = 0.034). These findings highlight the notable impact of thyroid function on mental health outcomes.

Conclusions

Treatment satisfaction remains suboptimal for patients with residual symptoms of hypothyroidism. TSQ especially seems to be a useful tool to recognize these residual symptoms. The further use of this tool to identify patients with residual symptoms may enable future studies to test the role of oral T3 in such patients given the strong negative correlation.