Neuropathy of Impaired Glucose Tolerance and Its Measurement

Impaired glucose tolerance (IGT) was originally shown in the prospective Whitehall Study (1) to carry an increased risk of large-vessel disease only. Whether or not IGT may also confer an increased risk for microvascular complications is not clear. Although microalbuminuria has been shown to be increased in those with IGT compared with control subjects (2), the incidence of retinopathy (IGT 6.7% vs. NGT 5.8%) (3) and moderate neuropathy (IGT 5.7% vs. NGT 2.8%) (4) have been found to be similar. Nevertheless, it has been proposed that IGT may cause neuropathy (5). However, little is new in clinical medicine; over 40 years ago Ellenberg (see ref. 5) suggested that neuropathy may indeed occur in pre-diabetes, although it is interesting that the interpretation was that factors other than hyperglycemia may cause the neuropathy. The recent resurgence of interest in IGT neuropathy is based on four separate studies of patients with idiopathic small-fiber neuropathy, where the prevalence of IGT was found to be 34–35.6%, three times the prevalence in age-matched control subjects (5). We believe the interpretation of these studies has significant limitations because the populations studied were selected for the presence of idiopathic small-fiber neuropathy, rather than IGT. Furthermore, as pointed out by Dyck et al. (6) in a critical review, the association between IGT and neuropathy remains to be confirmed in an ongoing prospective study. Added to this the relationship between the metabolic syndrome, and its component constituents, to IGT neuropathy has come under scrutiny. …