Thyroid antibodies in northern Norway: prevalence, persistence and relevance.
OBJECTIVE
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.


METHODS
A cross-sectional and longitudinal study based on the Tromsø Study in 1979-80 and 1986-87.


METHODS
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.
Bryhni
B
B
Department of Medicine, University Hospital of Tromsø, Norway.
Aanderud
S
S
Sundsfjord
J
J
Rekvig
O P
OP
Jorde
R
R
D000328:Adult; D001323:Autoantibodies / Q000097:blood*; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007037:Hypothyroidism / Q000453:epidemiology / Q000276:immunology*; D008137:Longitudinal Studies; D008297:Male; D008861:Microsomes / Q000276:immunology; D009664:Norway / Q000453:epidemiology; D015995:Prevalence; D011863:Radioimmunoassay; D013954:Thyroglobulin / Q000276:immunology; D013961:Thyroid Gland / Q000276:immunology*; D013967:Thyroiditis, Autoimmune / Q000453:epidemiology / Q000276:immunology*
D001323:Autoantibodies; D013954:Thyroglobulin