Endocrine disorders with ataxia of Friedreich. Causes of diabetes

Approximately 40% of patients with Friedreich’s ataxia have impaired glucose tolerance; diabetes is observed in 10-20% of patients (Harding A.E., Hebinck J. et al.). Diabetes mellitus with Friedreich ataxia is mitochondrial in nature and is caused by pancreatic dysfunction and impaired insulin secretion (Fantus I. et al.). Moreover, in patients, as a rule, there are no signs of autoimmune destruction of b-cells of the pancreas (Schoenle E. et al.). Typically, diabetes develops after the onset of neurological symptoms of the disease, approximately 10 years after the onset of the disease (Watkins P. et al.). Diabetes is insulin-dependent in nature, patients often develop diabetic ketoacidosis. Laboratory subclinical or, less commonly, clear clinical signs of a carbohydrate metabolism disorder can be detected with high frequency in heterozygous carriers of expansion of trinucleotide GAA repeats in the FRDA gene, which explains the observed high incidence of diabetes among relatives of patients with Friedreich’s ataxia (Hebinck J. et al.). Confirmation of the foregoing can serve as several examined families, weighed down by Friedreich’s ataxia. As can be seen in the genealogy schemes, in one of these families the proband mother suffered from type 2 diabetes mellitus, and in the other family, the proband father, his uncle and grandmother from the mother’s side, had diabetes mellitus. Other endocrine disorders, occasionally observed in patients with Friedreich’s ataxia, include hypogonadism, ovarian dysfunction, infantilism, and stunting. Violation of normal growth is more often observed in cases where the disease manifests itself at an early age (up to 10 years) and is characterized by rapid progression. A symptom of polyphagia is rare, but extremely interesting from the point of view of the pathophysiology of the disease. We first described such a patient (Ershova M.V.). Polyphagy – excessive food intake – can be observed either in the presence of “energy hunger” and hypoglycemia, or as a result of a violation of the central regulation of the food reflex (that is, with inadequate irritation of the food center of the hypothalamus). Apparently, with Friedreich’s ataxia under conditions of systemic ATP deficiency, polyphagy is a compensatory reaction, which allows one to increase the supply of energy sources to cells. It is also possible that this symptom occurs due to endocrinopathy, hormonal-mediator disorders in the hypothalamic region of the brain. Polyphagy is very characteristic of diabetes mellitus, but diabetes was not detected in the patient that we observed. It should be noted that the increased appetite in this patient was accompanied by a clearly progressive loss of body weight.

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