Diabetes Mellitus, Kidney Disease, and Sense of Taste

In addition to the outstanding review article by Prof. Hummel and colleagues (1) we would like to mention a recent review on the topic of genetic causes of congenital hypogonadism which describes in detail how dysfunction in the sense of smell is connected to certain genetic defects such as mutations in the genes ANOS1, SOX10, FEZF1, NDNF, TUBB3, and others (2). Furthermore, amongst endocrinological disorders diabetes mellitus can be associated with olfactory dysfunction, especially in patients with diabetic late complications. This might in part explain why patients with chronic or end stage renal disease also often have olfactory deficits, as the main reasons for chronic kidney disease are diabetes mellitus and/or hypertension (3). In a proof of concept, open-label clinical trial using the application of intranasal theophylline, more than 70% of patients with chronic kidney disease stage 4/5 showed an improvement in their sense of smell. A renal transplant in patients with chronic renal disease can also normalize the sense of smell in such patients and have a positive impact on their quality of life and social life. As pointed out by Prof. Hummel and colleagues when relating to the retronasal route in the perception of complex aromas and the so-called “fine taste”, the sense of smell and the sense of taste are closely interconnected with each other. Springer Verlag has published a special guest issue on the topic “The Sense of Taste in Endocrinology” in the journal Reviews of Endocrine and Metabolic Disorders (4). Similar to patients with mild cognitive disturbances in whom a reduction in the sense of smell counts as a sign for conversion to dementia, assessing the ability and intensity of the sense of smell in patients with diabetes mellitus and impaired renal function may be helpful, considering that diabetic patients often suffer microinfarctions of brain and heart which can promote the development of dementia if a cerebral infarction occurred in the frontotemporal region.