Hyperthyroidism : incidence and long term quality-of-life

Abstract

Hyperthyroidism is a common disorder which in general affects approximately 2 % of women and 0.2 % of men. There are three main types of hyperthyroidism, caused by increased thyroid hormone production: Graves disease, toxic multinodular goitre and solitary toxic adenoma. Three main treatment modalities are common for Graves hyperthyroidism: surgery, radioiodine, or antithyroid drugs. The aim of this thesis was to investigate the incidence of hyperthyroidism and the possible influence of the choice of treatment for Graves hyperthyroidism on health-related aspects of quality of life after 14-21 years, furthermore, to study whether patients with a history of hyperthyroidism, especially Graves disease, have an increased risk of committing suicide later in life.

In the first study, the total, age-specific incidence and the incidence of subgroups of hyperthyroidism in the county of Stockholm were determined during the years 2003-2005. They were identified by the clinical status, the thyroid hormone and antibody levels and in some cases by thyroid scintigraphy. Eight specialised units/hospitals in the county of Stockholm participated in the registration. During this period 1431 new well defined cases of hyperthyroidism on adults, >= 18 years of age were diagnosed. The total annual incidence was found to be 32.7/100 000. The annual incidence of Graves disease was 24.5/100 000, of toxic nodular goitre 3.3/100 000 and of solitary toxic adenoma 4.9/100 000.

In the second and third, studies we focused on long-term differences in health-related aspects of quality of life of patients who had been randomised in 1983-1990 to treatment with antithyroid drugs, surgery, or radioiodine for Graves hyperthyroidism. The treatment groups were compared with an age-and sex-matched Swedish reference population and with one another. We also addressed the question whether the quality of life was influenced by the current thyroidal hormonal status or the level of thyroxine (T4) substitution. Two quality of life questionnaires (36-item Short Form Health Status Survey (SF-36) and Quality of Life 2004 (QoL2004)) were answered by the patients and hormonal status was recorded. The results showed a lower SF-36 score on mental aspects of quality of life (p< 0.05) and vitality (p< 0.05) compared with a reference Swedish population. There were no differences in quality of life score between the three modes of treatment for Graves hyperthyroidism. We also found that the results obtained with SF-36 were not related to the current serum levels of thyroid hormones, as subjects with suppressed S-TSH reported QoL scores above as well as below the average score for the general reference population in both physical component summary and mental component summary.

In the fourth study, the risk of suicide among patients with a history of hyperthyroidism was investigated, since a pilot study had indicated an elevated suicide rate among patients previously treated for Graves hyperthyroidism. A comprehensive retrospective cohort study was therefore performed. The cohort included 43 633 patients who had been treated with radioiodine or surgically for hyperthyroidism in the years 1950-2005. The number of observed deaths in the cohort was compared with the expected, based on the suicide death rate in the age-, gender- and calendar period-matched general Swedish population, yielding standardised mortality ratios (SMR). The total SMR was 1.24 (95% CI, 1.04-1.47). The overall SMR among men and women with a history of Graves disease was 1.35 (95% CI, 1.07 - 1.66). A likely increase in risk of suicide among patients with a history of hyperthyroidism was observed.