Is Thyroid Autoimmunity per se a Determinant of Quality of Life in Patients with Autoimmune Hypothyroidism?

Abstract

Purpose: To evaluate the relationship between thyroid variables and health-related quality of life (QoL) in patients with autoimmune hypothyroidism, using the thyroid-specific QoL questionnaire ThyPRO.

Methods: In a cross-sectional study, responses to the ThyPRO from 199 outpatients with autoimmune hypothyroidism were analyzed in relation to thyroid volume, thyroid function and markers of thyroid autoimmunity. Based on a classical QoL framework, we hypothesized that physiological dysfunction caused specific physical and psychological symptoms, which affected functioning and well-being, and consequently participation in life and QoL. These hypotheses were tested through multiple regression and multivariate path analysis models.

Results: None of the thyroid function tests were associated with QoL scores. However, in the pairwise regression, the thyroid peroxidase antibody (TPOAb) level was associated with several QoL outcomes: Goitre Symptoms (p = 0.024), Depressivity (p = 0.004), Anxiety (p = 0.004), Emotional Susceptibility (p = 0.005) and Impaired Social Life (p = 0.047). In the multivariate model, the TPOAb level was related to Goitre Symptoms (r = 0.17, p = 0.019), Depressivity (r = 0.24, p = 0.001), and Anxiety (r = 0.23, p = 0.002), but no longer to Emotional Susceptibility or Impaired Social Life, indicating that the effect on these were mediated through an effect on the symptom scales (i.e. Goitre Symptoms, Depressivity and Anxiety).

Conclusion: Health-related QoL, evaluated with state-of-the-art QoL methodology, was related to TPOAb level but not to thyroid function. This raises the hypothesis that autoimmunity, independent of thyroid function, impacts on QoL in patients with autoimmune hypothyroidism, especially in terms of psychological symptoms. Longitudinal studies, in initially untreated patients, are needed to test this hypothesis.

Keywords: Autoimmune hypothyroidism; Autoimmunity; Clinical variables; Quality of life.

Fig. 1

Conceptual model linking the ThyPRO QoL scales with the relevant clinical variables. To the left are pathophysiological mechanisms involved in thyroid diseases and the clinical variables representing these mechanisms. The 13 scales, with the number of items in each scale in parentheses, are organized in their respective overall categories. TSHRAb = TSH receptor antibody. ¹ Not relevant in this sample, but included in the figure for completeness of the model.

Fig. 2

Results of the multivariate path analysis. ThyPRO scales are ordered in accordance with the theoretical QoL model. Standardized regression coefficients estimating the strength of the association are presented along each association arrow. Standardization implies that e.g. an increase of 1 SD in TPOAb leads to a 0.24-SD increase in Depressivity.