Japanese thyroid specialists chose LT4 as first line treatment for hypothyroidism in accordance with current guidelines, with LT3+LT4 combination use less frequent than in other countries, whereas use of thyroid hormones for non-hypothyroid indications is similarly high worldwide and not necessarily in accord with pertinent society guidelines.
Key Findings
Results
LT4 monotherapy was the first-line treatment for hypothyroidism chosen by all respondents.
100% of respondents selected LT4 as first-line treatment for hypothyroidism.
Anonymous responses from 207 of 874 (23.7%) JTA-certified thyroid specialists were analyzed.
The survey was based on the THESIS (Treatment of Hypothyroidism in Europe by Specialists: An International Survey) questionnaire adapted for Japan.
Respondents were members of the Japan Thyroid Association (JTA).
Results
A minority of Japanese thyroid specialists would use LT3 alone or in combination with LT4 for hypothyroid patients.
18.8% of respondents would use LT3 monotherapy.
28.0% would use LT3 + LT4 combination therapy.
LT3 + LT4 combination was preferred for patients on LT4 with residual symptoms or low serum T3 levels.
The use of LT3 + LT4 combination is described as less frequent in Japan than in other countries.
Results
Psychological factors and comorbidities were considered the main contributors to residual symptoms in hypothyroid patients on LT4.
Respondents identified psychological factors and comorbidities as the primary explanations for residual symptoms in patients treated with LT4.
This finding was noted in the context of deciding when to use combination LT3 + LT4 therapy.
Results
A substantial proportion of Japanese thyroid specialists would prescribe thyroid hormones to euthyroid women with infertility and positive anti-thyroid antibodies.
46.9% of respondents would prescribe thyroid hormones for female infertility with positive anti-thyroid antibodies.
This represents a non-hypothyroid indication for thyroid hormone use.
Such prescribing practice is described as not necessarily in accord with pertinent society guidelines.
Results
Many Japanese thyroid specialists would prescribe thyroid hormones to euthyroid pregnant or infertile women with TSH between 2.5–4 mU/L.
43.0% would prescribe thyroid hormones to pregnant women with TSH between 2.5–4 mU/L and negative anti-thyroid antibodies.
76.8% would prescribe to pregnant women with TSH between 2.5–4 mU/L and positive anti-thyroid antibodies.
46.9% would prescribe to infertile women with TSH between 2.5–4 mU/L and negative anti-thyroid antibodies.
77.3% would prescribe to infertile women with TSH between 2.5–4 mU/L and positive anti-thyroid antibodies.
Results
A notable proportion of Japanese thyroid specialists would prescribe thyroid hormones for Hashimoto's disease with a large goiter in euthyroid patients.
29.0% of respondents would prescribe thyroid hormones for Hashimoto's disease with a huge goiter in euthyroid subjects.
This represents another non-hypothyroid indication identified in the survey.
Such use is described as not necessarily in accord with pertinent society guidelines.
Conclusions
The use of thyroid hormones for non-hypothyroid indications among Japanese specialists is similarly high compared to other countries worldwide.
The survey explicitly compared Japanese practices to international data from the THESIS survey conducted in Europe.
While LT3 + LT4 combination use was less frequent in Japan than in other countries, non-hypothyroid indications for thyroid hormone use were described as 'similarly high worldwide.'
The paper notes these practices are 'not necessarily in accord with pertinent society guidelines.'
Nagayama Y, Tajiri J, Murakami T, Watanabe N, Sato S, Shindo H, et al.. (2025). A questionnaire survey of thyroid specialists in Japan on the use of thyroid hormones in hypothyroid and euthyroid patients.. Endocrine journal. https://doi.org/10.1507/endocrj.EJ25-0106