Insulin resistance in noncirrhotic idiopathic portal hypertension. To explore further the pathogenesis of glucose intolerance and insulin resistance observed in patients with cirrhosis and portal hypertension, we studied a 35-year-old woman with presinusoidal portal hypertension without cirrhosis due to nodular regenerative hyperplasia of the liver. After oral glucose ingestion, glucose tolerance remained normal; however, this occurred at the expense of a markedly hyperinsulinemic plasma response, suggesting the presence of insulin resistance. To examine this question more directly, we performed a stepwise euglycemic insulin clamp study in combination with an infusion of [6-3H]glucose and [1-14C]palmitate and indirect calorimetry. The ability of insulin to promote total body (primarily muscle) glucose uptake was markedly impaired, whereas its effect to suppress hepatic glucose production was normal compared with results obtained in nine healthy subjects. Moreover, insulin failed to normally suppress plasma free fatty acid turnover and oxidation in this patient. This informative case demonstrates that portal hypertension alone, without hepatic dysfunction from cirrhosis, is associated with impaired insulin-mediated glucose and plasma free fatty acid metabolism and may also play a predominant role in the development of insulin resistance in many cirrhotic patients. 