Incidence of hyperthyroidism in Slovenia since improved iodine supply

Full text: Since the year 1953, when iodine prophylaxis was introduced in Slovenia, several epidemiological studies confirmed the existence of mild iodine deficiency on the whole territory of Slovenia. In January 1999 the implementation of higher iodine content (25 mg of KI or 32 mg of KIO3) was recommended and since then the increased incidence of thyrotoxicosis was observed. Here we present 5-year follow-up data of the incidence of hyperthyroidism due to thyroid autonomy and Graves' disease. We estimated incidence rates from 1997 to 2001 for hyperthyroidism due to thyroid autonomy and Graves' disease among 1000000 people, living in the area of Ljubljana. We assumed that most cases were seen and treated in the Outpatient Department for thyroid diseases of Department for Nuclear Medicine of University Medical Centre Ljubljana. Immediately after correction of iodine deficiency, the incidence of hyperthyroidism due to thyroid autonomy rose almost twice in 1999 (320 cases in 1999 compared to 173 cases in 1997), but afterwards the incidence slightly decreased (240 cases in 2000). Similarly, the incidence of Graves' disease rose in 1999 (267 cases in 1999 compared to 237 in 1997) and in contrast to thyroid autonomy the incidence further increased in the following years (337 in 2000 and 246 in the first half of 2001). The increased incidence of hyperthyroidism due to thyroid autonomy and Graves' disease after elevation of iodine prophylaxis in Slovenia is comparable with data in some other endemic areas. Those data indicate that stepwise supplementation is preferable to immediate corrections. However, we believe that iodine prophylaxis is reasonable and justified and to reassess the iodine nutrition status we plan a follow up evaluation in year 2002. (author)