A questionnaire survey of thyroid specialists in Japan on the use of thyroid hormones in hypothyroid and euthyroid patients.

Levothyroxine (LT4) is the established treatment for hypothyroidism but some controversies, such as whether combining it with liothyronine (LT3) for hypothyroid patients and whether prescribing it to euthyroid patients, exist on its use. This survey was conducted to investigate current trends about thyroid hormone use in hypothyroid and euthyroid patients in Japan. Members of the Japan Thyroid Association (JTA) were invited to participate in an online questionnaire based on the THESIS (Treatment of Hypothyroidism in Europe by Specialists: An International Survey) survey. Anonymous responses from 207 of 874 (23.7%) JTA-certified thyroid specialists were analyzed. LT4 was the first line treatment for hypothyroidism by all respondents. 18.8% and 28.0% would also use LT3 and LT3 + LT4 combination, respectively. LT3 + LT4 combination was preferred for patients on LT4 with residual symptoms or low serum T3 levels. Psychological factors and comorbidities were considered as the main contributors to residual symptoms. Respondents would prescribe thyroid hormones in euthyroid subjects for female infertility with positive anti-thyroid antibodies (46.9%), for Hashimoto's disease with a huge goiter (29.0%), and for pregnant or infertile women with TSH between 2.5-4 mU/L irrespective of anti-thyroid antibody status (43.0 and 76.8%, and 46.9 and 77.3%, respectively). In conclusion, Japanese thyroid specialists chose LT4 as first line treatment for hypothyroidism in accordance with current guidelines. The use of LT3 + LT4 combination is less frequent in Japan than in other countries, whereas the use of thyroid hormones for non-hypothyroid indications is similarly high worldwide, which is not necessarily in accord with pertinent society guidelines.