Hashimoto's Thyroiditis Affects Symptom Load and Quality of Life Unrelated to Hypothyroidism: A Prospective Case-Control Study in Women Undergoing Thyroidectomy for Benign Goiter

Background: Hashimoto's thyroiditis (HT) is a common disease, and is the most prevalent cause of hypothyroidism. Symptoms and diseases associated with HT are considered to be caused by hypothyroidism. We hypothesized that higher antithyroperoxidase (anti-TPO) antibody levels would be associated with an increased symptom load and a decreased quality of life in a female euthyroid patient collective. Methods: In a prospective cohort study 426 consecutive euthyroid female patients undergoing thyroid surgery for benign thyroid disease were included. Main outcome measures were preoperative anti-TPO levels, a symptom questionnaire and the SF-36 questionnaire, and lymphocytic infiltration of the thyroid tissue as evaluated by histology. Results: Histology revealed HT in 28/426 (6.6%) subjects. To maximize the sum of the predictive values, a cutoff point for anti-TPO of 121.0 IU/mL was calculated (sensitivity 93.3% [95% confidence interval: 77.9%-99.0%]; specificity 94.7% [ 95% confidence interval: 92.0%-96.7%]) to predict the presence of histological signs of HT. The mean number of reported symptoms was significantly higher in patients with anti-TPO levels >121.0 IU/mL than in the other group (6.7 +/- 2.5 vs. 4.1 +/- 2.8; p<0.001). There were no differences in preoperative thyroid-stimulating hormone levels (1.7 +/- 1.3 vs. 1.5 +/- 1.4 mu U/mL, respectively; p = 0.155). Chronic fatigue, dry hair, chronic irritability, chronic nervousness, a history of breast cancer and early miscarriage, and lower quality-of-life levels were significantly associated with anti-TPO levels exceeding the cut-off point (p<0.05). Conclusions: Women with HT suffer from a high symptom load. Hypothyroidism is only a contributing factor to the development of associated conditions.