Screening for Sulphonylureas in the Investigation of Hypoglycaemia

Abstract

SUMMARYThe most important cause of hypoglycaemia in the presence of high insulin and C-peptide concentrations is insulinoma. However, a similar picture arises from use of sulphonylureas, which is sometimes covert. All specimens received in two years by a supraregional assay service laboratory from adults with low glucose and inappropriately high insulin and C-peptide concentrations were tested for sulphonylureas by a radioimmunoassay that employed antibodies to glibenclamide. In sulphonylurea-positive cases a questionnaire was sent to the consultant responsible for the patient, to elicit further information.Samples from 93 adult patients met the criteria, and 34 (37%) of these gave a positive result on screening for sulphonylureas. The consultants provided further information on 31 of the 34, and in 20 the presence of a sulphonylurea was unexpected. In 10 the features were such as to raise the possibility of factitious drug ingestion.A simple screening technique applied to specimens from patients with hyperinsulinaemic hypoglycaemia indicated that, in a substantial proportion of cases, the patient was taking a sulphonylurea.

Unwitnessed sulphonylurea poisoning in a healthy toddler

“…In those with inappropriately high serum insulin and C-peptide levels, insulinoma [13] and sulphonylurea ingestion [10] are important causes to be considered. Insulinomas are small tumours which are often difficult to locate due to limitations in imaging techniques [20] that may lead to unnecessary partial pancreatectomy [6].…”

“…Estimation of sulfonylurea concentrations should be undertaken when a history of potentially available sources of oral hypoglycaemia agents is elicited from carers [18]. We and others [10] recommend routine screening for sulphonylureas in all children with inappropriately raised plasma insulin and C-peptide levels. Discordant insulin and Cpeptide ratio suggests the possibility of autoimmune insulin syndrome [1] or factitious hypoglycaemia.…”

Munchausen syndrome and factitious disorder: the role of the laboratory in its detection and diagnosis

“…In one study, positive sulphonylurea screens were found on 31 out of 94 samples previously obtained during hyperinsulinaemic hypoglycaemic episodes. 53 Of these samples, 10 were identified as relating to possible cases of factitious drug ingestion -a diagnosis which had not been considered at the time. 53 When exogenous insulin has been administered to induce hypoglycaemia, the insulin concentration is high whereas C-peptide and pro-insulin concentrations are low.…”

“…53 Of these samples, 10 were identified as relating to possible cases of factitious drug ingestion -a diagnosis which had not been considered at the time. 53 When exogenous insulin has been administered to induce hypoglycaemia, the insulin concentration is high whereas C-peptide and pro-insulin concentrations are low. Furthermore, the plasma insulin concentration is typically .100 mU/L following exogenous administration, while in fasted insulinoma patients the insulin concentration does not tend to exceed 20 mU/L.…”

“…53 Of these samples, 10 were identified as relating to possible cases of factitious drug ingestion – a diagnosis which had not been considered at the time. 53…”