Anti-thyroidal peroxidase antibodies are associated with thyrotropin levels in hypothyroid patients and in euthyroid individuals.

OBJECTIVE: The study was designed to evaluate the relationship between thyroid antibodies and gland dysfunction, with the aim of finding a clinically useful threshold value of thyreoperoxidase antibodies, which could prove to be predictive for thyroid failure.

MATERIAL AND METHODS: The study was conducted on 99 women, ages ranging from 18-91 years (mean age: 45.5 ±17.0), were treated as outpatients in the Department of Endocrinology, Metabolism and Internal Medicine. Analysis of serum samples for TSH concentration and anti-TPO titers was conducted.

RESULTS: The most common disorder was hypothyroidism. Anti-TPO titers above reference range values were observed in 35 patients (35.4%): 21 (60%) were hypothyroid and 11 (31.4 %) were euthyroid. The anti-TPO and TSH serum levels correlated both in patients with high thyroid antibody titers, and in the anti-TPO negative groups. To find the threshold value of anti- TPO that would help predict hypothyroidism, receiver operating curves were used. With this approach, TPO antibody titers over 17 IU/ml indicated hypothyroidism with a 90% sensitivity and 75% sensibility.

CONCLUSIONS: It can be postulated that the cutoff values of anti-TPO in the general population should be decreased in order to improve autoimmune thyroid disorder screening. Obviously, using that margin may lead initially to the detection of some false positive subjects. However, with lower cut-off values, more patients can be enrolled into thyroid follow-up groups. In this way, many people could avoid complications of undiagnosed, insidious thyroid failure.