The article is devoted to the analysis of a clinical case of the severe hypothyroidism. A review of the “clinical masks” of the hypothyroidism is presented. The examination of the polymorbid patients should include the level of thyroid-stimulating hormone and thyroid hormones. The untimely initiation of substitution therapy is associated with a poor prognosis, and the early start of the treatment is a guarantee of saving the life of a patient with severe hypothyroidism.