Role of the Oral Glucose Tolerance Test (OGTT) in the idiopathic restless legs syndrome.

Background: Restless legs syndrome (RLS) is a sensorimotor disorder characterised by a distressing urge to move the legs. Several clinical conditions have been associated with RLS, such as iron deficiency, uraemia, pregnancy, polyneuropathy and Diabetes Mellitus (DM). However the causes remain unknown in about 70-80% of cases.

Objective: To evaluate the role of glucose metabolism abnormalities in idiopathic RLS.

Methods: We enrolled 132 consecutive patients with idiopathic RLS associated with normal fasting glycaemia and 128 control subjects. We evaluated glucose and insulin levels after a 2-h oral glucose tolerance test (2h-OGTT) in patients and control subjects. In addition we determined Insulin Resistance (IR) by Homa-Index.

Results: After 2h-OGTT, the prevalence of glucose metabolism abnormalities was significantly higher in patients with RLS than in controls (P=.002). Impaired Glucose Tolerance (IGT) was found in 54 (41%) patients and in 23 (18%) controls, while a new-diagnosed DM (NDDM) was found in 25 (19%) patients and in 8 (6%) controls. The IR showed no significant differences between patients and controls.

Conclusions: Our study suggests that IGT (prediabetes) is frequently associated with idiopathic RLS. We propose to perform a 2h-OGTT in idiopathic RLS patients with normal fasting glycaemia.