Introduction. Hypothyroidism is a disease that occurs as a consequence of the lack of thyroid hormones in the body or the absence of their effects on cells. Hypothyroidism is at least twice as common in women as it is in men. Manifestation is the disorder of metabolism, which leads to a general slowing of mental and body functions. Hypothyroidism usually develops gradually. Symptoms may not appear until years after the thyroid has stopped functioning and they are often mistaken for signs of other illnesses, menopause or aging. Diagnosis is based on the patient's observations, medical history, physical examination, and thyroid function tests. Case report. This case report is about patient with severe form of hypothyroidism, which is sent to our institution for further treatment under the diagnosis of heart failure Conclusion. The fast diagnosis and appropriate and timely treatment prevented further deterioration with possible myxedematous coma, and therefore uncertain outcome.