Short summary

At least 10% of the patients with hypothyroidism have impaired quality of life despite biochemically euthyroidisme. The causes are unknown but are probably multifactorial including unrecognized comorbidity. The aim of this study is to investigate the prevalence of predefined diseases (comorbidities) in patients with hypothyroidism and the association of these comorbidities to quality of life measured with the disease-specific questionnaire ThyPRO and the generic questionnaire SF-36.

Rationale

Background: Hypothyroidism is a common disease. In Denmark, more than 150.000 patients are treated with life-long thyroid hormone substitution. The disease causes numerous symptoms including tiredness, cognitive deficit, depression, or muscle- and joint pain. The symptoms of hypothyroidism were believed to be fully reversible. However, it has been shown that at least 10% of the patients have impaired quality of life despite biochemically euthyroidisme. Compared to healthy people, hypothyroid patients have reduced ability to work, more frequent sick leave as well as increased risk of early retirement. The causes are unknown but are probably multifactorial including unrecognized comorbidity. Danish register studies have shown increased prevalence of somatic (e.g. lung and heart disease) as well as psychiatric diseases both before and after patients are diagnosed with hypothyroidism. Further, it is well known that patients with Hashimoto´s thyroiditis have increased risk of other autoimmune diseases e.g. celiac disease, pernicious anemia, vitiligo, diabetes mellitus type 1, Addison's disease and Sjogren's syndrome. Sleep apnea is a well-known cause of tiredness. Some studies have shown a significant prevalence of sleep apnea (25-35%) among patients with hypothyroidism. It is still unclear whether the reduced quality of life observed in hypothyroid patients is due to comorbidity or the thyroid disease per se. Given the high prevalence of comorbidity among patients with hypothyroidism, studies are needed in which hypothyroid patients systematically are screened for comorbidity and whether such conditions, if present, have impact on quality of life.

Objectives: To investigate the prevalence of predefined diseases (comorbidities) in patients with hypothyroidism and the association of these comorbidities to quality of life measured with the disease-specific questionnaire ThyPRO and the generic questionnaire SF-36.

Description of the cohort

Design and trial size: This study is a screening- and observational study on consecutively included patients with chronic hypothyroidism. The patients are systematically screened for several predefined common diseases, and which can lead to non-specific symptoms as those seen in hypothyroidism. The trial will include up to 100 participants.

Inclusion criteria: Chronic hypothyroidism; age: 18-79 years; biochemical euthyroidism defined by TSH within the reference range the previous 6 months; self-perceived reduced quality of life; ability to read or understand Danish; written informed consent; access to "E-boks". Exclusion criteria: Hypothyroidism due to previous thyroid cancer; significant somatic or psychiatric comorbidity based on clinical judgment (e.g. cancer, heart disease or psychosis); pregnancy or breast-feeding; inability to read or understand Danish; lack of informed consent.

Data and biological material

Outcomes: The screening will consist of blood tests analyzed for: B12 vitamin deficiency, iron deficiency, folic acid deficiency, adrenocortical insufficiency, vitamin D deficiency, celiac disease, Sjogrens´s syndrome, allergy (IgE), and diabetes mellitus. In addition, blood pressure is measured and screening for sleep apnea is performed. Quality of life is assessed at inclusion and after 3 months, using validated questionnaires (ThyPRO and SF-36).