Effects on the glutathione pool of the insulin-induced hypoglycaemia test

The growth hormone (GH) stimulation test shows that hypoglycaemia can cause the generation of free radicals, or reactive oxygen species (ROS), together with the migration of amino acids, glutathione and various ions to the interior of fat or muscle cells. The aim of the present study is to evaluate the splitting of plasma glutathione into its two fractions, oxidized (GSSG) and reduced (GSH), after the induction of hypoglycaemia with insulin in the course of the GH stimulation test. We studied 41 short children (47% boys and 53% girls) at the Paediatric Department of the San Cecilio Hospital (Granada, Spain) to evaluate their size and growth. A GH stimulation test using insulin-induced hypoglycaemia was carried out, and GSSG and GSH values in plasma were determined. The glutathione level is associated with the level of glucose reached at 30 min after initiating the test. This provoked an initial reduction in the GSH/GSSG ratio, which fell to a minimum at 30 min after starting the test, although the values rose again at 60 min. The results obtained show that the insulin-induced GH stimulation test produces a decrease in plasma levels of the glutathione pool, that persists at least for 2 hours following the beginning of the test.