Objective: While Germany was considered to be an iodine deficient area grade I to II in 1993, iodine supply has increased. With higher iodine uptake, prevalence of autoimmune thyroiditis may increase. Poor data exist on iodine supply and the occurrence of thyroid dysfunction in middle-aged adults in the western part of Germany. The aim of our study was to analyze iodine status, prevalence of TPO-antibodies (TPOab), TSH and fT4 levels in a large population-based sample in the western part of Germany.
Methods: Between 2001 and 2003 serum and casual urine samples were drawn from 4814 participants (50.2% women, 49.8% men, age 4575 years) of the Heinz Nixdorf Recall study and analyzed by routine laboratory tests. Assay reagents for TSH, fT4 and TPO-Ab were provided by Roche Diagnostics.
Results: We excluded participants with known thyroid disease, thyroid medication (including iodine-containing drugs) and elevated serum creatinine. Of the remaining 3527 persons, TSH and fT4 data were available from 3150 (89.3%). About 96.7% of men and 94.2% of women were euthyroid. Subclinical and overt hyperthyroidism was detected in 1.5 and 0.4% of male and 2.4 and 0.4% of female participants, respectively. About 1.2 and 0.2% of men and 2.2 and 0.8% of women exhibited subclinical and overt hypothyroidism. The median iodine excretion was 128 μg iodine/g creatinine (men: 113 μg/g, women: 152 μg/g; P<0.05). Iodine deficiency (<100 μg/g) was significantly more frequent in men than in women (37.9 vs 13.0%). High iodine excretion (more than 200 μg/g) was detected in 24.3% of women and 9.0% of men (P<0.01). Elevated TPOab (>200 U/ml) were also found significantly more frequent in women (5.4%) than in men (1.5%). In men, high TPOab titres were found particularly in those individuals with high iodine excretion (TPOab >200 U/ml in 2.9% of men with 200250 μg/g). Interestingly, in women TPOab >200 U/ml (6.8%) were detected primarily in individuals with an excretion of 100150 μg/g. About 69.6% (16/23) of women and 41.2% (7/17) of men with TSH levels >5 mU/l exhibited TPOab >200 U/ml. Neither in men nor in women iodine excretion was associated with TSH or fT4 levels.
Conclusion: Our data demonstrate that iodine supply in the Western Part of Germany has normalized. In men, elevated TPO antibodies were associated with high iodine excretion.