INAPPROPRIATELY ELEVATED PLASMA INSULIN-LIKE GROWTH FACTOR-II IN RELATION TO SUPPRESSED INSULIN-LIKE GROWTH FACTOR-I IN THE DIAGNOSIS OF NON-ISLET CELL TUMOR HYPOGLYCEMIA

The diagnosis of non‐islet cell tumour (hypoinsulinaemic) hypoglycaemia has been complicated by contradictory biochemical evidence. Although insulin‐like growth factor II (IGF‐II) has been identified as the hypoglycaemic agent, plasma levels are often not elevated. In this study specific radioimmunoassay procedures for the measurement of IGF‐I and IGF‐II are described. Reference data on plasma IGF‐II concentrations in relation to a wide range of IGF‐I levels have been accumulated using plasma samples from acromegalic, hypopituitary and insulinoma (i.e. hyperinsulinaemic hypoglycaemia) patients as well as normal subjects from all age groups. The reference data indicate that a low plasma IGF‐I value is normally associated with a relatively low plasma IGF‐II level. Within a group of hypoinsulinaemic hypoglycaemia patients, a small number, invariably with evidence of a neoplasm, had low plasma IGF‐I concentrations but apparently normal IGF‐II levels. We propose that, in such cases, an apparently normal plasma IGF‐II value is inappropriately high for the low plasma IGF‐I level and, in association with non‐ketotic hypoinsulinaemia and suppressed plasma growth hormone (GH), is diagnostic of a non‐islet cell tumour as the cause of hypoglycaemia. Copyright © 1990, Wiley Blackwell. All rights reserved