Endocrine Abstracts

Background: Few studies have scrutinized the spectrum of symptoms in subclinical hypothyroidism.

Methods: From three DanThyr cross-sectional surveys performed in the period 1997 to 2005, a total of 8,903 volunteers participated in a comprehensive investigation including blood samples and questionnaires on previous diseases, smoking habits, alcohol intake, and education. From the three surveys we included patients with unknown subclinical hypothyroidism (n=376) and euthyroid controls (n=7,619). For further comparison we also added patients newly diagnosed with autoimmune overt hypothyroidism (n=140) recruited from a previous study. We explored to which extent patients with subclinical hypothyroidism reported 13 previously identified hypothyroidism-associated symptoms (tiredness, dry skin, mood lability, constipation, palpitations, restlessness, shortness of breath, wheezing, globulus sensation, difficulty swallowing, hair loss, dizziness/vertigo, and anterior neck pain). In various uni- and multivariate regression models we searched for circumstances predicting why some patients have more complaints than others.

Results: Subclinically hypothyroid patients did not report higher hypothyroidism score ((median, IQR), 2 (0-4) vs. 2 (0-4), P=0.25) compared to euthyroid controls. Within the group of subclinical hypothyroid patients: co-morbidity had the highest impact on symptoms (tiredness, shortness of breath, wheezing; all P<0.001); TSH level had no impact on symptom score; low age was accompanied with higher mental burden (tiredness, P<0.001; mood lability, P<0.001; restlessness, P=0.012), whereas shortness of breath was associated with high BMI (P<0.001) and smoking (P=0.007).

Conclusion: Patients with a thyroid function test suggesting subclinical hypothyroidism do not express thyroid disease related symptoms more often than euthyroid subjects. In subclinical hypothyroidism, clinicians should focus on undiagnosed co-morbidity and should optimize treatment of known concomitant diseases rather than expecting symptomatic relief following levo-thyroxine substitution.