Thyroid antibodies in northern Norway: prevalence, persistence and relevance

• Published in: Journal of Internal Medicine
• Main Authors: BRYHNI, B., AANDERUD, S., SUNDSFJORD, J., REKVIG, O. P., JORDE, R.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1996
• Subjects: Norway; Tromsø; Northern Norway
• Online Access: http://dx.doi.org/10.1046/j.1365-2796.1996.488823000.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1046%2Fj.1365-2796.1996.488823000.x; https://onlinelibrary.wiley.com/doi/pdf/10.1046/j.1365-2796.1996.488823000.x

Objectives. To investigate the prevalence and persistence of thyroid autoantibodies in a population sample and to assess the development of biochemical hypothyroidism (defined as an elevated serum thyrotropin [TSH] concentration) in relation to their presence. Design and setting. A cross‐sectional and longitudinal study based on the Tromsø Study in 1979–80 and 1986–87. Subjects and main outcome measures. From 2551 random participants in 1979–80 aged 34±8.4 (mean±SD) years, sera were available in 2513 and 2504 persons for determination by passive haemagglutination of the antibody to thyroid microsomal antigen (anti‐Tm) and of the antibody to thyroglobulin (anti‐Tg). Total thyroxine (TT4) and TSH were measured in 114 of 176 antibody‐positive subjects and in 101 controls. After 7 years, anti‐Tm and anti‐Tg were remeasured in 1939 and 1931 subjects, and TT4 and TSH in 92 of the initially antibody‐positive subjects and in 69 controls. Results. Anti‐Tm occurred more frequently than anti‐Tg (in 6.1 vs. 2.8%; P <0.001). Anti‐Tm ( P< 0.001) and anti‐Tg ( P =0.027) were both more common in women than in men. The prevalence of anti‐Tm ( P =0.025), but not of anti‐Tg, increased with age. Changes in titre levels after 7 years were mostly small or moderate. Both in women ( P = 0.005) and in men ( P <0.001) the TSH concentrations increased with increasing levels of anti‐Tm, whereas in men, the concentrations also increased with increasing anti‐Tg levels ( P <0.001). Biochemical hypothyroidism developed with a 2.7% yearly incidence only in antibody‐positive subjects, all except one of whom had anti‐Tm. Conclusions. The prevalences of thyroid antibodies were comparable to those found in similar studies in other areas. Their presence was associated with the development of biochemical hypothyroidism.