Myotonic dystrophy (MD) is the most common muscle disorder in adults. MD is a hereditary disease with an autosomal dominant mode of inheritance, almost 100% penetrance and pronounced clinical polymorphism. The mechanism for the development of the disease is that a mutation of the DMPK (dystrophia myotonica protein kinase) gene disrupts the normal metabolism of RNA, which leads to a defect in the maturation and translation of mRNA. The disorder in the DMPK gene affects not only striated musculature, but also smooth myocytes and cardiomyocytes. The main clinical symptom that distinguishes MD from others is a spontaneous or provoked inability to relax muscles (myotonia phenomenon). Endocrine disorders arising from type 1 MD (MD1) with a higher than average frequency in the population include hypergonadotropic hypogonadism, impaired glucose tolerance with hyperinsulinism, and insulin resistance. Thyroid function may remain normal, although many cases of autoimmune thyroiditis resulting in hypothyroidism, as well as Graves’ disease, have been described. A description is given of a patient suffering from MD1 with a number of endocrine disorders, including hypergonadotropic hypogonadism, autoimmune thyroid disease, hyperinsulinism, and also impaired calcium-phosphorus metabolism. Important features are the absence of any significant complaints from the muscular system in the presence of an increase in creatine phosphokinase (CPK), which is characteristic of this disease, as well as the temporal dynamics of thyroid status and the nature of the autoimmune thyroid disease.