Value of Low Levels of Anti-TPO Antibodies in Patients With Suspicion of Hashimoto Thyroiditis

Abstract

In clinical practice, many patients do not show the full symptoms of Hashimoto thyroiditis. The titer of the anti-TPO antibodies (ATAB) is often detectable but not pathologically elevated. This study evaluates the clinical status of patients with low ATAB titers.Sixty-eight consecutive patients (55 female, 13 male; age: 24 -84 years; mean: 55.4 years) with detectable titers of ATAB were investigated by clinical status, ultrasound, and thyroid scintigraphy with Tc-99m.Eighteen patients had pathologically elevated titers of ATAB. Fifty-eight patients with detectable ATAB titers had clinical symptoms, 46 hypoechoic tissue by ultrasound, 17 a decrease in thyroid gland volume, and 14 a thyroid-stimulating hormone Ͼ2.5 mU/L.Patients with low titers of ATAB and thyroid-stimulating hormone values in the upper reference interval (Ͼ2.5 mU/L) can have symptoms compatible with thyroid dysfunction and deserve a trial of therapy. (The Endocrinologist 2007;17: 83-84) T he National Academy of Clinical Biochemistry has altered the upper bound of the normal range of thyroid-stimulating hormone (TSHb) in their guidelines from 4.0 mU/L down to 2.5 mU/L. 1 The natural history of patients with findings typical for Hashimoto thyroiditis is described in this paper. MATERIALS AND METHODS PatientsSixty-eight consecutive patients (55 female, 13 male; age: 24 -84 years; mean: 55.4 years) who presented with detectable titers of anti-TPO antibodies (ATAB) were studied with regard to clinical status, ultrasound (US), and thyroid scintigraphy (TS) with Tc-99m. Fifty healthy subjects served as controls. MethodsThyroid-related symptoms, prior thyroid history of surgery, radioiodine therapy, or medication were recorded together with the clinical thyroid examination.Inclusion criteria are no intravenous contrast media in the last 2 months, no preceding thyroid surgery, detectable amount of ATAB, absence of focal autonomous nodules, and findings defined during a physical examination of the thyroid gland, including scintigraphy.Free thyronine (fT3), free thyroxine (fT4), TSHb, and ATAB were measured. Two subgroups were defined by the range of ATAB titers:• Group 1: ATAB detectable but less than 60 U/mL • Group 2: ATAB Ͼ60 U/mLThe level of anti-TSH-receptor antibody (TRAB) was determined in 45 cases.Ultrasonography was performed with a convex 5-MHz probe using a Picker LC 7000A scanner. The thyroid volume was calculated using length ϫ width ϫ depth ϫ 0.5. A decrease in thyroid volume was considered to be 6 mL or more in female patients and 9 mL or more in male patients. 2 TS was performed 20 minutes after the i.v. injection of 60 MBq of technetium-99m pertechnetate. The images were acquired in the sitting position over 5 minutes. SPSS Rel. 11 was used on a personal computer. The level of significance was set at 0.05 (2-tailed P). Nonparametric correlation coefficients (Spearman) were applied to nonparametric data. RESULTSEighty-six percent of the patients in the group with minimally elevated ATAB titers were symptomatic (Table 1). A decrease in ech...