Introduction: The incidence of hyperthyroidism has been reported in various countries to be 23-93/100 000 inhabitants per year. This extended study has evaluated the incidence for w40% of the Swedish population of 9 million inhabitants. Sweden is considered to be iodine sufficient country. Methods: All patients including children, who were newly diagnosed with overt hyperthyroidism in the years [2003][2004][2005], were prospectively registered in a multicenter study. The inclusion criteria are as follows: clinical symptoms and/or signs of hyperthyroidism with plasma TSH concentration below 0.2 mIE/l and increased plasma levels of free/total triiodothyronine and/or free/total thyroxine. Patients with relapse of hyperthyroidism or thyroiditis were not included. The diagnosis of Graves' disease (GD), toxic multinodular goiter (TMNG) and solitary toxic adenoma (STA), smoking, initial treatment, occurrence of thyroid-associated eye symptoms/signs, and demographic data were registered. Results: A total of 2916 patients were diagnosed with de novo hyperthyroidism showing the total incidence of 27.6/100 000 inhabitants per year. The incidence of GD was 21.0/100 000 and toxic nodular goiter (TNGZSTACTMNG) occurred in 692 patients, corresponding to an annual incidence of 6.5/100 000. The incidence was higher in women compared with men (4.2:1). Seventy-five percent of the patients were diagnosed with GD, in whom thyroid-associated eye symptoms/signs occurred during diagnosis in every fifth patient. Geographical differences were observed. Conclusion: The incidence of hyperthyroidism in Sweden is in a lower range compared with international reports. Seventy-five percent of patients with hyperthyroidism had GD and 20% of them had thyroid-associated eye symptoms/signs during diagnosis. The observed geographical differences require further studies.

In 49% of pregnant women on thyroxine substitution, serum TSH values were outside the reference range when first tested, generally in the first trimester. Fetal loss was significantly greater in pregnant women with abnormal TSH values compared to those with normal TSH values. Thyroid function in pregnant women on thyroxine substitution should be monitored early in pregnancy and carefully followed during pregnancy. The thyroxine dose should be increased as needed early in pregnancy to avoid hypothyroidism.

Patients with low thyroid peroxidase antibodies (anti-TPO) and increased TSH-receptor antibodies (TRAb) at diagnosis of Graves' disease (GD) have been suggested to have an increased risk to develop Graves' ophthalmopathy (GO). The aim was to evaluate if GO development can be predicted.This is an observational study with registration of possible GD and GO risk factors.399 patients with GD were registered 2003-2008 in Malmö, Sweden and out of these 310 were retrospectively followed up to 6 years. The main outcome measures were anti-TPO titer, TRAb titer, smoking habits, radioiodine treatment and GO development.TRAb was assessed with a third generation assay at GD diagnosis in 231 patients. The proportion of patients with GO increased above the median 6.3 IU/L both at diagnosis of GD (p=0.001) and at follow-up (p=0.0001).The distribution of GO patients anti-TPO above or below 20 kIU/L at diagnosis of GD was similar between groups (p=0.239). However at follow-up anti-TPO<20 kIU/L was associated with an increased proportion of newly developed GO as compared to the cohort with anti-TPO>20 kIU/L (p=0.018).87% of patients who developed GO after GD diagnosis had TRAb above 6.3 IU/L and/or anti-TPO below 20 kIU/L. The proportion of GO was doubled in GD patients treated with radioiodine but could not explain the described findingsAnti-TPO<20 kIU/L and/or TRAb>6.3 IE/L at the time of GD diagnosis were associated with an increased risk to develop GO after diagnosis of GD.