[Features of the use of synthetic analogues of thyroid hormones: а 2020 THESIS* questionnaire survey of members of the Belarusian Public Medical Association of Endocrinology and Metabolism].

Background: The standard treatment for hypothyroidism is levothyroxine (LT4), which in the Republic of Belarus is available in tablet form whereas liothyronine (LT3) is not registered, but patients can purchase them on their own abroad.

Aim: This study aimed to investigate Belarusian endocrinologists' attitude of thyroid hormones in hypothyroid and euthyroid patients.

Materials And Methods: An online survey was conducted, for which members of the Belarusian Medical Association of Endocrinology and Metabolism were invited by posting information in the group chat and by e-mail. The research period was from October 1 to December 26, 2020. 210 questionnaires were received, 146 of which were used.

Results: The majority of participants, 145 (99.3%), indicated that they were using LT4 as the first-choice drug for the treatment hypothyroidism. Sixty-one (41.8%) doctors answered that LT3 + LT4 combination likely can be used in patients with long-term untreated hypothyroidism and 15 (10.3%) - in patients with persistent symptoms of hypothyroidism, despite biochemical euthyroidism on therapy LT4. Over half of the respondents 84 (57.5%) answered that thyroid hormone therapy was never indicated for euthyroid patients, but 50 (34.2%) would consider it for female infertility with high level of thyroid antibodies and 36 (24.7%) for simple goiter growing over time. In various conditions that could interfere with absorption of LT4, most responding Belarusian endocrinologists do not expect a significant difference with different formulations (tablets+"I do not expect major changes in different forms" vs. "soft gel capsules"+"liquid solution"; p <0.001). Persistent symptoms of hypothyroidism on the background of LT4 replacement therapy with the achievement of the target TSH can mainly be caused by psychosocial factors, concomitant diseases, unrealistic patient expectations, chronic fatigue syndrome, and the burden of chronic disease.

Conclusion: The method of choice of Belarusian endocrinologists in the treatment of hypothyroidism is LT4 replacement therapy, but the appointment of LT4 + LT3 combination therapy can be considered in certain clinical situations. As a rule, endocrinologists do not prescribe LT4 in patients with euthyroidism and do not expect a significant difference when using other forms of levothyroxine.