Incidence of hyperthyroidism in Sweden

Area of Science:

• Endocrinology
• Epidemiology
• Public Health

Background:

• Hyperthyroidism incidence varies globally, reported between 23-93/100,000 inhabitants annually.
• This study assesses hyperthyroidism incidence in Sweden, an iodine-sufficient country, covering approximately 40% of its 9 million population.

Purpose of the Study:

• To determine the incidence of newly diagnosed overt hyperthyroidism in Sweden.
• To identify the etiological distribution of hyperthyroidism, including Graves' disease and toxic nodular goiter.
• To investigate demographic factors and the occurrence of thyroid-associated eye symptoms.

Main Methods:

• Prospective multicenter registration of hyperthyroidism patients (2003-2005).
• Inclusion criteria: clinical hyperthyroidism signs/symptoms, low TSH (<0.2 mIE/l), and elevated thyroid hormones.
• Exclusion criteria: recurrent hyperthyroidism or thyroiditis. Data collected: diagnosis (Graves' disease, toxic multinodular goiter, solitary toxic adenoma), smoking, treatment, eye symptoms, demographics.

Main Results:

• Total incidence of de novo hyperthyroidism was 27.6/100,000 inhabitants/year.
• Graves' disease incidence was 21.0/100,000; toxic nodular goiter incidence was 6.5/100,000.
• Incidence higher in women (4.2:1 ratio). Graves' disease comprised 75% of cases; 20% had eye symptoms. Geographical variations observed.

Conclusions:

• Swedish hyperthyroidism incidence is lower than previously reported internationally.
• Graves' disease is the predominant cause (75%), with 20% experiencing eye symptoms at diagnosis.
• Observed geographical differences warrant further investigation.