Endocrine Abstracts

Background: Although a number of studies show that the serum levels of antithyroid peroxidase antibodies (TPO-Ab) in patients with Hashimoto’s thyroiditis decline during levothyroxine treatment, only a few provide quantitative data. The objective of the present study was to provide this information.

Methods: This was a retrospective study of TPO-Ab concentrations in 44 women and 4 men (median age 45.5 years; range 17–76 years) with Hashimoto’s thyroiditis as defined by the following criteria: elevated plasma TPO-Ab and typical hypoechogenicity of the thyroid in high-resolution sonography at first presentation or during follow-up. The decrease in percentage of the TPO-ab level during follow-up was calculated.

Results: At the study entry 31 had elevated TSH and L-thyroxine treatment was started. Ten became hypothyroid in follow-up, and then L-thyroxine treatment was started. The remaining 7 patient followed without treatment (median 4 years). The 41 patients who started L-thyroxine treatment were analysed in quartiles based on duration of L-thyroxine treatment. In the first quartile, the median decrease in TPO-ab level was 57.8% (follow-up≤1.5 years). The median decrease in TPO-ab level was similar in all groups receiving L-thyroxine (in the second quartile 54.7%, follow-up duration was 1.5–3 years; in the third quartile 57.4%, follow-up duration 3–7 years; in the last quartile was 55.9%, follow-up >7 years). The median decrease in TPO-ab level was 33.7% in Hashimoto thyroditis group without treatment. Although the number of patients without treatment was small, yet it was statistically significant (P=0.02).

Conclusions: TPO-ab immediately decreases following the start of L-thyroxine treatment for Hashimoto thyroiditis, and the decrease remain stable during long-term follow-up.