OBJECTIVE To compare the outcome of different treatment options used in several cases of non-islet cell tumour hypoglycaemia (NICTH).PATIENTS Eight cases of NICTH were referred for diagnosis and monitoring following either surgical or medical treatment.METHODS Serum samples collected throughout the time-course of each case were analysed for glucose, insulin, C-peptide, IGF-I, total IGF-II, total IGF-II to IGF-I ratio and, in most of the cases, big IGF-II.RESULTS Surgical excision was successful in the relief of symptoms and normalization of the biochemical parameters. Therapeutic treatment with glucocorticoids confirmed previous studies showing the suppressive effect on tumour (big) IGF-II production. The present data show that the effect was dose-dependent and reversible if doses were below a critical level.CONCLUSIONS Within the limits of the cases studied, and the time-scales involved, moderate- to high-dose glucocorticoid therapy had immediate beneficial influence on symptomatic hypoglycaemia and, if tolerated in the long term, was effective in correcting the underlying biochemical dysfunction, unlike other therapeutic regimens. This effectiveness was only achieved when the dose exceeded a threshold level specific to the patient. In addition, reduction of the dose or withdrawal of the drug caused a return of the abnormal biochemical profile. Surgical removal of the malignancy, where this was an option, was successful within the periods studied.

Adult spontaneous hypoglycaemia is not a diagnosis per se but a manifestation of a disease. Although rare, it is important to identify spontaneous hypoglycaemia and its causes because treatment may be preventative or curative. Hypoglycaemia can occur as an epiphenomenon in many serious diseases. It is sufficient to recognise the disease's association with hypoglycaemia and then take appropriate action to prevent the recurrence of hypoglycaemia. In investigating apparently healthy individuals, common pitfalls to avoid are: failure to recognise subacute neuroglycopenia clinically; failure to document hypoglycaemia adequately during symptoms; failure to measure pancreatic hormones, counter-regulatory hormones, and ketones in hypoglycaemic samples; failure to recognise pre-analytical and analytical limitations of laboratory assays; and failure to abandon obsolete and inappropriate investigations. Providing these caveats are met, appropriate laboratory and radiological investigations will almost always uncover the cause of spontaneous hypoglycaemia.

Background and methods: We report a case of insulinoma in which the diagnosis was very challenging as some of the biochemical data were consistently equivocal. In order to assess the relative reliability of the analytical tests, retrospective biochemical data on 45 other cases of histologically confirmed insulinoma were evaluated, enabling the most secure diagnostic process to be identified. Results: The data showed that insulin concentrations alone, although measurable, were equivocal in 17% of cases. The addition of C-peptide values clarified the diagnosis in about 50% of the borderline cases, whilst ketone (β-hydroxybutyrate) concentrations were low during the prevailing hypoglycaemia in all cases. Conclusion: The combination of these three tests is suggested as the most effective method for the biochemical diagnosis of hypoglycaemia due to insulinoma.

Aim: To assess the extent to which biochemical analytical services contribute to the diagnosis and management of clinical cases of hypoglycaemia.Methods: All cases of confirmed hypoglycaemia, referred during a six month period, were included in the survey.Questionnaires were sent to each referring laboratory requesting information on the clinical progress and current status of the patient.Results: The level of influence exerted by analytical data was assigned in each case and those with similar outcomes combined.Identifiable case groups were: (1) Results not recorded in the patients' notes (15.7%).( 2) Inappropriate requesting of insulin and C peptide measurements in cases of diabetes (11.4%).( 3) Patient died soon after investigation (20.0%).( 4) Patient recovered spontaneously (17.1%).( 5) Patient received effective medical or surgical treatment (12.9%).( 6) Patient awaiting or not requiring pathology based treatment (31.4%).( 7) Inconclusive outcome prompting further investigation (5.7%).Conclusions: Within the timescale of the survey (approximately 12 months), positive progress had been made towards diagnosis and subsequent treatment in only 10% of cases.Another 30% were either awaiting some form of treatment or further diagnostic tests.The remaining 60% did not appear to benefit in any way from the biochemical investigations.. . . . .

The 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.

Hypoglycemia occurs as an epiphenomenon in many serious diseases and further investigation may be unnecessary. In other, often seemingly healthy individuals, it is responsible for their presenting symptoms. In them preliminary diagnosis depends on demonstrating a low blood glucose concentration during spontaneous symptoms by ambulatory self-collection of capillary blood and its analysis for glucose in the laboratory. Subsequent investigation requires appropriate plasma hormone analysis on blood collected while the patient is hypoglycemic.

Therapeutically administered antidiabetic drugs, notably insulin and the sulfonylureas, are undoubtedly the most common cause of hypoglycemia encountered in clinical practice. Nevertheless, an impressive list of other drugs can produce hypoglycemia unpredictably in seemingly healthy individuals in whom it may masquerade as spontaneous hypoglycemia. Unless the true cause is identified when the patient is first seen, fruitless and expensive overinvestigation may ensue. The most important drugs are discussed herein and brief mention made of those for which coincidence has not been eliminated.

Alcohol- and drug-induced hypoglycemia can, unless recognized in the course of a patient's illness, lead to expensive and fruitless over-investigation or even death.

The report by Hoekman et al. (1999) in this issue adds another piece to the jigsaw that is the complex biochemical syndrome known as non-islet cell tumour hypoglycaemia (NICTH). Many tumour types have been shown over recent years to be associated with the disorder (Marks & Teale, 1998), far beyond early observations that it was restricted mainly to retroperitoneal fibrosarcomas. Hypoglycaemia has long been associated with large tumours and was ascribed to increased glucose utilisation. The application of gene probe technology to examination of tumour tissue focused attention on IGF-II as the hypoglycaemic agent (Daughaday et al., 1988). Despite overexpression by the tumour tissue (Daughaday, 1995), the measurement of serum IGF-II concentrations was usually reported as being ‘normal’. Concomitantly, IGF-I levels were suppressed as a consequence of the induced GH deficiency. On this basis the diagnostic value of IGF-II to IGF-I molar ratios was recognised as being of importance (Teale & Marks, 1990). Subsequently, wider biochemical profiles have been compiled as being typical of the syndrome. Although IGF-II does not reflect GH secretion with the same close control as IGF-I, its serum levels are nevertheless low in other conditions where there is GH deficiency or the GH-IGF axis is dysfunctional, often as a result of a catabolic disorder. Chromatographic analysis of serum from NICTH cases has revealed that the ‘normal’ serum IGF-II levels comprise an expectedly low amount of mature IGF-II, the remainder being immature (big) IGF-II which cross-reacts with all IGF-II RIA methods. The present studies by Hoekman et al. provide another variation on this clinical theme. They report that the big IGF-II is associated mainly with 60 kD complexes, presumably in binary complexes with IGFBPs, although evidence in the form of size-exclusion chromatographic profile demonstrating this is unfortunately not presented in detail. Recent studies from this laboratory (Teale & Marks, 1998) have shown that in several cases of NICTH immunoreactive IGF-II, predominantly the big form, does not co-elute with the major IGFBP peaks but is mainly in a free form. Whilst IGFBP-6 was not measured in these studies it could be speculated that it would elute with IGFBP-2 and IGFBP-3, being of similar size. This assumption could also have been examined by Hoekman using detailed chromatographic profiles. There is the intriguing possibility that IGFBP-6 is a tumour-specific binding protein which is present normally at insignificant concentrations and exerts a relatively unknown metabolic influence (Jones & Clemmons, 1995). Evidence that serum levels of IGFBP-2 are invariably elevated in NICTH and are not generated by tumour tissue has been reported previously and confirmed by Hoekman et al. (1999). Malnutrition and catabolic states in general have been noted to cause subnormal serum levels of IGFBP-3 and IGFs, inducing apparently compensatory increases in IGFBP-2. It is significant that this rise in IGFBP-2 still occurs despite the presence of abnormally high amounts of IGFBP-6.

We describe a case of non-islet cell tumour hypoglycaemia (NICTH) associated with a renal cell carcinoma. Serum insulin-like growth factors (IGFs) (including IGF-II E peptide), IGF-binding proteins (IGFBPs), insulin and C-peptide were measured before and after surgical removal of the tumour. IGFBPs were visualized by Western ligand blotting. Preoperatively ‘big’ IGF-II and IGFBP-2 levels were raised. IGF-I, IGFBP-1 and IGFBP-3 were low, while insulin, C-peptide and GH were undetectable. These changes were reversed by 2 days postoperatively. Protease assays showed little IGFBP-3 protease activity preoperatively. Preoperatively, neutral chromatography demonstrated most of the immunoassayable IGFBP-3 in a high molecular weight form with a small amount of IGF-II. Most of the IGF-II and big IGF-II eluted in lower molecular weight forms. Postoperative samples showed a shift in IGF-II which became increasingly associated with IGFBP-3 in both low and high molecular weight complexes. By Northern blotting, expression of all species of IGF-II mRNA in the tumour was 10-fold greater than in normal human liver. The tumour did not express IGFBP-1 or IGFBP-2. IGFBP-3 was expressed in small amounts, while the expression of IGFBP-4 was two-fold higher than in liver. In conclusion, we have confirmed high levels of big IGF-II and IGFBP-2 in NICTH, changes which are reversed postoperatively. The IGF-II is derived from the tumour which overexpresses these genes but IGFBP-2 probably arises from extratumour upregulation.

OBJECTIVE To assess the relative efficacy of hGH and glucocorticoids in the treatment of non-islet cell tumour hypoglycaemia (NICTH) by examination of their influence on the composition of the various molecular species involving tumour and mature forms of IGF-II in association with IGFBP-3.DESIGN Two groups each of 4 patients, all diagnosed as cases of NICTH, were treated with either hGH or glucocorticoids. Through the use of acidic size exclusion chromatography serum levels of tumour (big) and mature IGF-II were evaluated. Neutral size exclusion chromatography was used in the separation of molecular species before assay for immunoreactive IGF-II and IGFBP-3 content.RESULTS High-dose hGH treatment produced increases in serum levels of big and mature IGF-II and IGFBP-3 but without generation of high molecular weight complexes, Glucocorticoid treatment suppressed big IGF-II permitting re-establishment of normal IGF/IGFBP association patterns.CONCLUSION Glucocorticoid therapy has been demonstrated to consistently reverse the biochemical abnormalities caused by tumour-derived big IGF-II compared with the potentially adverse stimulatory effects of hGH treatment in causing increases in serum levels of big IGF-II.

OBJECTIVEIGF‐I and IGF binding protein (IGFBP)‐3 levels in man are positively regulated by GH status; in contrast, evidence suggests an inverse relationship between GH status and IGFBP‐2. We investigated the effects of somatropin administration on the serum concentrations of these analytes, together with serum and urinary concentrations of GH, to evaluate their potential as markers in the development of a test for detecting doping with GH in sports competitors.DESIGNSomatropin was administered subcutaneously at a dose of 0.15 U/kg bodyweight/day at 1000 h for 3 days to eight healthy men (20–32 years old).MEASUREMENTSSerum concentrations of GH, IGF‐I, IGFBP‐2 and ‐3 were determined in blood samples collected at 1600 h on the days prior to (day −1), during (days 0, 1 and 2), and following administration (days 3 and 7). Urine was collected continuously from days −2 to 3 and then on day 7.RESULTSSerum and urinary concentrations of GH were only raised on the days of administration whereas, following cessation of somatropin, the increases in the serum concentrations of IGF‐I and IGFBP‐3 were sustained for at least 1 day (30 h). Serum IGFBP‐2 decreased during the period of administration and was still suppressed on day 3. The concentration ratios of IGFBP‐3 to IGFBP‐2 and IGF‐I to IGFBP‐2 increased markedly with administration and both ratios were still significantly augmented compared with basal values 30 h after the last administration.CONCLUSIONWith acute administration of somatropin to healthy men the serum concentration of IGFBP‐2 decreases and the ratios of serum IGF‐I/IGFBP‐2 and IGFBP‐3/IGFBP‐2 increase. These ratios should be considered in the development of a test for detecting somatropin administration in sport.

We investigated whether pancreatic beta-cell dysfunction has a role in the pathogenesis of glucose intolerance in acromegaly by comparing plasma intact proinsulin, immunoreactive insulin, C-peptide and glucose concentrations during a 75 g oral glucose load in six patients with active acromegaly and eight healthy volunteers. Only acromegalic patients with normal glucose tolerance were studied. Glucose concentrations were similar in acromegalic patients and controls. Acromegalic patients had higher fasting insulin (P < 0.005) and fasting C-peptide (P < 0.005) concentrations than controls. Although fasting proinsulin levels were higher in acromegalic patients than controls, this did not achieve statistical significance. Integrated insulin (P < 0.05), C-peptide (P < 0.05) and proinsulin (P < 0.005) concentrations were greater in acromegalic patients than control subjects. Integrated (P < 0.05) proinsulin:insulin molar ratios were higher in acromegalic patients than controls. Fasting and integrated insulin:C-peptide molar ratios were similar in acromegalic patients and controls. These results indicate that hyperproinsulinaemia contributes to the hyperinsulinaemia which characterizes active acromegaly. The disproportionate hyperproinsulinaemia in acromegaly suggests that prolonged and excessive growth hormone secretion may result in pancreatic beta-cell dysfunction which may predispose acromegalic subjects to glucose intolerance.

Laron-type dwarfism, I a syndrome of growth hormone (GH) receptor deficiency, is an autosomal recessive disorder caused by a variable genetic defect of the GH receptor.s-' The phenotype of the patients with Laron-type dwarfism (LTD) resembles isolated GH deficiency." LTO is characterized by extremely low serum insulin-like growth factor-I (IGF-I) despite normal or high concentrations of biologically active GH and by resistance to exogenous GH. 5 The defect in the GH receptor results in deficiencies of IGF-I, IGF-II, and IGF-binding protein-3 (IGFBP-3), the major serum carrier protein of IGF peptides.s? Purification and protein sequencing revealed that serum growth hormone binding protein (GHBP) was structurally identical to the extracellular hormone binding domain of the membrane-bound GH receptor." The GHBP was noted to be absent in some LTO patientsv'" and normal in others. II We present here an unusual case of GH receptor defect and the members of two unconnected families, one with three siblings with LTO and GHBP-negative phenotype and the other with one child with LTO and GHBPpositive phenotype.

OBJECTIVE While the effects of age on the growth hormone/insulin‐like growth factor (IGF) axis are well documented, the influence of ethnic background is unknown. The differences in IGF and IGF binding proteins (IGFBPs) were investigated in two ethnic groups. DESIGN A cross‐sectional study of an age‐selected cohort of healthy, normoglycaemic, non‐obese Caucasian (C) and Asian (A) subjects. PATIENTS Fifty‐three (27 C, 26 A) subjects with a mean age (±SD) of 20.6±0.8 years were studied. MEASUREMENTS Fasting measurements of glucose, insulin, IGF‐I, IGF‐II, IGFBP‐1 and IGFBP‐3. Western ligand blotting and immunoblotting with IGFBP‐2 and IGFBP‐3 of serum samples. RESULTS There were no significant differences in IGF‐I levels between Caucasian and Asian subjects (C 218±55 vs A 229±40μg/l; P=0.44). IGF‐II (C 707±110 vs A 583±75μg/l; P<0.0001) and IGFBP‐3 (C 5.9±1.2 vs A 5.12±1.17 mg/l; P=0.01) levels were significantly higher in Caucasian subjects. Immunoblotting of ligand blots revealed no protease activity on either IGFBP‐3 or IGFBP‐2 to account for these ethnic differences. CONCLUSIONS Ethnic differences in IGFBP‐3 and associated IGF‐II levels may affect the inter‐relationships of IGFs and their binding proteins and need to be considered when interpreting IGF data on growth and metabolism.

A patient presented with frequent episodes of spontaneous hypoglycaemia due to a solitary fibrous tumour of pleural origin, secreting incompletely processed pro‐insulin‐like growth factor II (big IGF‐II). Somatostatin receptors were demonstrated in the tumour by 111In‐labelled octreotide scintigraphy, but despite maximal doses of octreotide, there was no suppression of big IGF‐II secretion and the hypoglycaemia persisted. The combination of GH and glucocorticoid therapy abolished the hypoglycaemia.

Selected combinations of tests for growth hormone and the growth mediating peptides, insulin-like growth factors, and their binding proteins have improved the diagnostic reliability of the procedures used in the investigation of growth abnormalities (GH deficiency, GH and IGF receptor deficiencies, GH excess, diabetes, or undernutrition) and in malignancies associated with hypoglycemia.

With the menopause a decrease in serum IGF-l levels occurs which is thought to be due to the withdrawal of the effect of oestrogen (Romagnoli, Minisola, Carnavale, Scarda, Rosso, Scarnecchia, Pacitti and Mazzuoli 1993). However, oral oestrogen therapy of various preparations have been shown to decrease serum IGF-l in postmenopausal women after short term administration (Dawson-Hughes, Stern, Goldman and Reich/in 1986; Kelly, Rajkovic, O'Sullivan, Sernia and Ho 1993); an effect which has been attributed to first pass hepatic metabolism.