Hypothyroidism or subclinical hypothyroidism affects 4 to 21% of the female population and 3 to 16% of the male population . Standard treatment for the highly prevalent condition is replacement of thyroid hormone by levothyroxine, artificial free thyroxine (fT4) . The definition of the targeted normal range of thyroid hormone level is, however, still under debate [3–5]. Moreover, it has been reported that among patients receiving this treatment, well-being is reduced even if euthyroidism is reestablished [6, 7].
It is still an open issue where patients’ reports of unwanted symptoms result from . Explanations discussed are independent effects of thyroid autoimmunity, the most common cause of hypothyroidism [9–11], insufficient normalisation of thyroid hormone levels at target tissues such as the brain despite normal serum hormone levels , selection bias in seeking health care  or reactive processes to the awareness of having a chronic disease . Disentangling these possible causes has important implications for treatment targets in this large patient group. Crucial for successfully addressing the above issue is the use of appropriate instruments to measure patient-reported outcomes. It is important to differentiate between perceived health status, psychological well-being and quality of life as well as between generic and disease-specific instruments [15, 16]. All are valid and important constructs to address patient-reported outcomes but should be carefully distinguished to avoid misleading interpretation of results. Symptom load has for example often been interpreted as quality of life although perceived symptoms may or may not influence quality of life in an individual [15, 16]. Health status is often confusingly referred to as health-related quality of life . It has been shown for several clinical conditions such as peripheral arterial disease or heart failure that disease-specific questionnaires are more sensitive to change [18, 19]. However, most studies still use exclusively generic questionnaires and often self-constructed symptom lists to assess patient-reported outcomes in hypothyroidism, so reducing sensitivity to subtle effects and comparability across studies [20–23].
The first hypothyroidism-specific instruments have been developed and validated in recent years including the Thyroid-Dependent Quality of Life Questionnaire (ThyDQoL) [24, 25]. The ThyDQoL measures the impact of hypothyroidism on quality of life in general and in selected domains tailored to the disease and to individual realities by including importance ratings for each domain. The Underactive Thyroid Symptom Rating Questionnaire (ThySRQ) is in contrast a measure of hypothyroidism-related symptoms and symptom bother . Finally, the Thyroid Treatment Satisfaction Questionnaire (ThyTSQ) measures disease-specific treatment satisfaction [24, 26]. It is designed to cover hypothyroidism-specific aspects such as satisfaction with current medication and dose.
All three hypothyroidism-specific questionnaires have been developed and validated in English and use of the questionnaires in any other language needs validation in an independent sample to examine psychometric validity. Although necessary, this is a demanding and time consuming procedure, possibly contributing to the paucity of validated translations. However, despite known advantages over the use of exclusively generic or non-validated instruments, the original questionnaires are also relatively new, which may account for the fact that they are not yet in widespread use. None of the validated hypothyroidism-specific questionnaires available has been evaluated for German so far, although interest in the field is high in German speaking countries [10, 21–23, 27].
We are thus introducing the first three hypothyroidism-specific PROMs in German to improve the array of tools available for future research. We provide detailed psychometric data including internal consistency and factor structure of the questionnaires, as well as hypothesised subgroup analyses. According to the literature we expect more negative reports in patients with thyroid stimulating hormone (TSH) in the upper normal range  and more negative reports in patients with hypothyroidism of autoimmune origin [10, 27].
In addition, we have used the questionnaires in a clinical study including 18 adequately treated patients with hypothyroidism due to autoimmune thyroiditis (Hashimoto’s disease) and 18 healthy control subjects. The study also included a number of well-known generic PROMs. Thereby, we were able to investigate construct validity of the new questionnaires and feasibility in a clinical context. We expect disease-specific and generic instruments to be moderately correlated because similar, though distinct, constructs are targeted. The clinical study included assessment of TSH, fT4, free triiodothyronine (fT3) as well as thyroid peroxidase antibodies (TPOAb) and thyroglobulin antibodies (TgAb). This design allowed investigation of the relationship between PROMs and biochemical thyroid hormone status.