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BACKGROUND. Various types of hypothyroidism require different doses of levothyroxine in order to establish euthyroid state. However, previous studies frequently did not define the type of hypothyroidism and the factors influencing the adequacy of treatment. Therefore, the aim of the present study was to evaluate the treatment with levothyroxine in different well-defined types of hypothyroidism in greater detail. METHODS. In our retrospective study, we included data from medical records of 1,122 patients, who were followed between 2011 and 2014 due to various types of treated hypothyroidism. We acquired the data on the type of hypothyroidism, the age and gender of patients, on the weekly dose of levothyroxine, and we evaluated the adequacy of treatment. RESULTS. The most frequent type of hypothyroidism was hypothyroidism because of Hashimoto’s thyroiditis (72.9%), followed by hypothyroidism after radioiodine treatment (15.6%), after thyroidectomy (6.9%), and iatrogenic hypothyroidism (4.6%). Groups of patients with various types of hypothyroidism statistically significantly differed with respect to age, gender and weekly dose of levothyroxine (p < 0.001 for all comparisons). The highest portion of adequately treated disease was established in patients after radioiodine (77.7%), who were clinically most frequently followed, while the lowest portion was established in patients after thyroidectomy (55.8%). Groups with adequately and inadequately treated hypothyroidism did not differ with respect to age (p = 0.339). The ratio between the number of women and men was significantly higher in the group with adequately than in the group with inadequately treated hypothyroidism (p < 0.001). CONCLUSIONS. In patients after thyroidectomy and in men, thyroid hormone replacement therapy of hypothyroidism should be monitored more carefully.