Subclinical hypothyroidism does not exacerbate symptoms, says study

Thyroid disease-related symptoms do not occur more frequently in patients with a thyroid function test suggesting subclinical hypothyroidism compared to those with euthyroidism, a study has shown.

A total of 8,903 individuals participated in a comprehensive investigation, including blood samples and questionnaires on previous diseases, smoking habits, alcohol intake, and education, from three Danish Investigation on Iodine Intake and Thyroid Diseases (DanThyr) cross-sectional surveys performed from 1997 to 2005.

The authors included 376 patients with subclinical hypothyroidism and 7,619 euthyroid controls from the three surveys. They then explored to what extent subclinical hypothyroid patients reported 13 previously identified hypothyroidism-related symptoms (eg, tiredness, dry skin, mood lability, constipation, palpitations, restlessness, shortness of breath, wheezing, globus sensation, difficulty swallowing, hair loss, dizziness/vertigo, and anterior neck pain).

Finally, circumstances predicting why some patients had more complaints than others were searched in various univariate and multivariate regression models.

Patients with subclinical hypothyroidism did not report higher hypothyroidism score (median, 2 vs 2; p=0.25) relative to euthyroid controls.

Among patients with subclinical hypothyroidism, comorbidity was found to have the greatest impact on symptoms (tiredness, shortness of breath, wheezing; p_all<0.001). TSH level showed no effect on symptom score, and younger age was associated with higher mental burden (tiredness, p<0.001; mood lability, p<0.001; restlessness, p=0.012). On the other hand, high body mass index (p<0.001) and smoking (p=0.007) correlated with shortness of breath.

“In subclinical hypothyroidism, clinicians should focus on concomitant diseases rather than expecting symptomatic relief following levothyroxine substitution,” the authors said.