Column chromatographic characterization of complex formation of pro-IGF-II isoforms with acid labile subunit and IGF-binding proteins associated with non-islet cell tumour induced hypoglycaemia.

OBJECTIVE AND DESIGN: Non-islet cell tumour induced hypoglycaemia (NICTH) is a paraneoplastic phenomenon that is associated with the formation of several isoforms of pro-insulin like growth factor 2 (pro-IGF-II), or so called "big" IGF-II. Disturbance of ternary complex formation by big IGF-II is assumed to be a crucial early event in the pathogenic cascade of hypoglycaemia. By size-exclusion chromatography, we investigated complex formation by adding different naturally occurring isoforms of pro-IGF-II to pooled normal adult serum. Results were compared with the analysis of the serum from a patient with NICTH. RESULTS: Gel filtration experiments with the serum of a patient with NICTH demonstrated that ternary complex formation was severely compromised. The various forms of pro-IGF-II did not induce a shift of IGF-binding protein 3 (IGFBP-3) from 150kD towards smaller binary complexes in the normal adult serum, suggesting that they did not interfere with the interaction between the acid labile subunit and IGFBP-3. Instead, unglycosylated recombinant pro-IGF-II[1-104] was capable of forming a 150kD complex. In contrast, predominantly glycosylated and unglycosylated pro-IGF-II[1-87] eluted in the free unbound form. We showed that mature IGF-II and isoforms of pro-IGF-II were able to phosphorylate the IGF-I receptors of MC7 cells, albeit to a markedly lesser extent than IGF-I. When the patient's serum was tested in this system, the IGF-I receptor phosphorylation activity was considerably less than that in sera from age matched healthy individuals. CONCLUSION: We postulate that, alongside the presence of big IGF-II in the circulation, additional steps are required to stimulate the release of IGF-II and pro-IGF-II isoforms from IGFBPs in vivo. These factors may be proteases, that are present in the local environment of the tumour and in insulin-sensitive tissues.

Deep brain stimulation - effects on swallowing function in Parkinson's disease.

OBJECTIVE: In patients with Parkinson's disease (PD), deep brain stimulation of the subthalamic nucleus (STN DBS) is well recognized in improving limb function, but the outcome on swallowing function has rarely been studied. The aim of this work was to evaluate the effect of STN DBS on pharyngeal swallowing function in patients with PD using self-estimation and fiberoptic endoscopic evaluation of swallowing. METHODS: Eleven patients (aged 41-72, median 61 years) were evaluated preoperatively and at 6 and 12 months after STN DBS surgery. All patients were evaluated with self-estimation on a visual analogue scale, and eight of them with a fiberoptic endoscopic examination with a predefined swallowing protocol including Rosenbek's Penetration-Aspiration Scale, Secretion Severity Scale, preswallow spillage, pharyngeal residue, and pharyngeal clearance. RESULTS: The self-assessments of swallowing function revealed a subjective improvement with STN DBS stimulation, whereas the data from the swallowing protocol did not show any significant effect of the STN DBS treatment itself. The prevalence of aspiration was not affected by the surgery. CONCLUSIONS: The results show that swallowing function was not negatively affected by STN DBS and the risk of aspiration did not increase. Self-estimation of swallowing function showed a subjective improvement due to stimulation.

Swallowing function in Parkinson's patients following Zona Incerta deep brain stimulation.

OBJECTIVE: The purpose of the present study was to examine whether there was a negative effect of caudal Zona Incerta deep brain stimulation (cZI DBS) on pharyngeal swallowing function in Parkinson's patients (PD). There are no former reports including swallowing and cZI DBS. METHODS: Eight patients (aged 49-71 years; median 62) were evaluated pre- and post-operatively, at 6 and 12 months after DBS surgery. Evaluation tools were fiberoptic endoscopic evaluation of swallowing examinations and patients' self-assessments of their swallowing function including a visual analog scale and quality-of-life-related questions. The swallowing protocol included Rosenbek's Penetration-Aspiration Scale, Secretion Severity Scale and parameters for preswallow spillage, pharyngeal residue, and pharyngeal clearance. RESULTS: There was no clear-cut effect of neurostimulation post-operatively at 6 and 12 months on any of the swallowing parameters except for the preswallow spillage that was slightly worsened in the stimulation on condition 12 months post-operatively. The answers to the self assessment questions did not vary significantly. CONCLUSIONS: The effect of the stimulation on the swallowing function varied among individuals, but the overall outcome was that cZI DBS did not seem to have a negative influence on swallowing function in the eight patients studied.

Insulin-like growth factors and insulin-like growth factor-binding proteins in relation to disease status and incidence of hypoglycaemia in patients with a gastrointestinal stromal tumour.

OBJECTIVE: Patients with a gastrointestinal stromal tumour (GIST) suffering from non-islet cell tumour-induced hypoglycaemia (NICTH), being associated with increased plasma levels of pro-insulin-like growth factor (IGF)-IIE[68-88], have been reported occasionally. We studied the clinical relevance of pro-IGF-IIE[68-88] and other IGF-related proteins in GIST patients. PATIENTS AND METHODS: Twenty-four patients were included. Plasma samples were collected before 1 week and median 5 months after start of treatment with imatinib, and levels of IGF-I, total IGF-II, pro-IGF-IIE[68-88], insulin-like growth factor-binding protein (IGFBP)-2, -3 and -6 were determined. GIST specimens from 17 patients and tumour cyst fluid from two patients were analysed for IGF-II and IGFBP-2. RESULTS: Before treatment and/or during follow-up, 3 of 24 (13%) patients showed increased plasma levels of pro-IGF-IIE[68-88]. All three developed NICTH. Overall, patients with metastatic disease, elevated serum lactate dehydrogenase activity or total tumour size >12 cm had the highest pro-IGF-IIE[68-88] levels. Most patients had increased plasma IGFBP-2 levels and these levels were significantly higher in patients with progressive disease. (Pro-)IGF-II was expressed in 82% of GISTs and IGFBP-2 only in one case. CONCLUSION: We identified pro-IGF-IIE[68-88] as a marker that may be used in the surveillance of GIST.

Growth hormone stimulates bone healing in a critical-sized bone defect model.

Growth hormone plays an important role in bone metabolism. Treating bone deficits is a major topic in orthopaedic surgery. Our hypothesis was that local continuous growth hormone administration stimulates bone healing in a canine critical-sized bone defect model. Bone formation in the defects was quantified using densitometric image analysis and histomorphometry. After growth hormone treatment, expression levels of insulin-like growth factors-I and II, and growth hormone receptor were determined in the bone regenerate of the original defects. Circulating plasma concentrations of insulin-like growth factors-I and II, and insulin- like growth factor binding proteins-4, and 6 were measured during treatment. Growth hormone administration resulted in healing of bone defects but without an additional effect of local infusion. Expression of insulin-like growth factor-I in the bone regenerate was lower in the growth hormone-treated dogs, whereas insulin-like growth factor-II and growth hormone receptor expression were not increased. Growth hormone increased circulating insulin-like growth factor-I and growth factor-II plasma concentrations. Continuous infusion of growth hormone stimulated bone healing in a canine critical-sized bone defect model. Local delivery of growth hormone did not additionally enhance bone healing. Increased circulating plasma concentrations of insulin-like growth factors-I and II most likely induced bone formation.

Non-hyperinsulinemic hypoglycemia in a patient with a gastrointestinal stromal tumor.

One of the authors (JvD) recently reported a case of non-islet cell tumor hypoglycemia caused by the production of "big" IGF-II by a gastrointestinal stromal tumor (GIST). Here, we report a patient with a GIST in whom non-hyperinsulinemic hypoglycemia was not attributable to aberrant tumoral IGF-II processing, but instead was caused by a combination of cachexia, renal and hepatic dysfunction, and tumoral glucose consumption.

Differential patterns of insulin-like growth factor-I and -II mRNA expression in medulloblastoma.

Insulin-like growth factors (IGFs) play an important role in tumour growth and development. We hypothesized that this is also the case for medulloblastomas, which are highly malignant cerebellar brain tumours usually occurring in children. In these tumours the expression patterns of IGF-I and -II mRNA were studied. Tumour specimens obtained from 12 children and two adults at diagnosis were hybridized in situ with digoxigenin-labelled cRNA probes for hIGF-I and hIGF-II mRNAs. In all cases, tumour cells showed abundant expression of IGF-I mRNA. Nine of the 14 tumours showed variable but significant IGF-II expression. In these tumours, the hybridization signal almost exclusively colocalized with a subpopulation of Ki-M1P positive cells that were identified as ramified microglia (RM) cells. In the five tumours without IGF-II expression, microglia/brain macrophages with a more rounded amoeboid-like morphology predominated. RM cells in normal cerebellar tissues, residing abundantly in areas of the white and, to a less extent, in the grey matter, were IGF-II mRNA-negative. These RM cells showed a thinner and more extensively branched appearance and were more evenly distributed than those encountered in medulloblastoma. Probably, during the transformation from the resting ramified towards the amoeboid morphology (or vice versa) IGF-II mRNA expression is only temporarily induced. The physiological meaning of the induction of IGF-II mRNA expression by these cells in medulloblastoma remains unclear but any IGF-II peptide synthesized could exert unfavourable mitogenic and antiapoptotic effects on adjacent tumour cells. However, in this relatively small number of cases we could not find any indications for a relationship between clinical characteristics of the various cases and the extent of IGF-II mRNA expression.

Treatment of haemangiopericytoma-associated hypoglycaemia with embolisation.

A 48-year-old woman with a known history of metastatic haemangiopericytoma presented with intractable hypoglycaemia. Hypoglycaemia was accompanied by undetectable serum insulin levels with high levels of proforms of insulin-like growth factor-II ('big' IGF-II). Reduction of tumour load with embolisation resulted in a normal pattern of serum glucose levels throughout the day.

Acute stress response in children with meningococcal sepsis: important differences in the growth hormone/insulin-like growth factor I axis between nonsurvivors and survivors.

Septic shock is the most severe clinical manifestation of meningococcal disease and is predominantly seen in children under 5 yr of age. Very limited research has been performed to elucidate the alterations of the GH/IGF-I axis in critically ill children. We evaluated the GH/IGF-I axis and the levels of IGF-binding proteins (IGFBPs), IGFBP-3 protease, glucose, insulin, and cytokines in 27 children with severe septic shock due to meningococcal sepsis during the first 3 d after admission. The median age was 22 months (range, 4-185 months). Eight patients died. Nonsurvivors had extremely high GH levels that were significant different compared with mean GH levels in survivors during a 6-h GH profile (131 vs. 7 mU/liter; P < 0.01). Significant differences were found between nonsurvivors and survivors for the levels of total IGF-I (2.6 vs. 5.6 nmol/liter), free IGF-I (0.003 vs. 0.012 nmol/liter), IGFBP-1 (44.3 vs. 8.9 nmol/liter), IGFBP-3 protease activity (61 vs. 32%), IL-6 (1200 vs. 50 ng/ml), and TNFalpha (34 vs. 5.3 pg/ml; P < 0.01). The pediatric risk of mortality score correlated significantly with levels of IGFBP-1, IGFBP-3 protease activity, IL-6, and TNFalpha (r = +0.45 to +0.69) and with levels of total IGF-I and free IGF-I (r = -0.44 and -0.55, respectively). Follow-up after 48 h in survivors showed an increased number of GH peaks, increased free IGF-I and IGFBP-3 levels, and lower IGFBP-1 levels compared with admission values. GH levels and IGFBP-1 levels were extremely elevated in nonsurvivors, whereas total and free IGF-I levels were markedly decreased and were accompanied by high levels of the cytokines IL-6 and TNFalpha. These values were different from those for the survivors. Based on these findings and literature data a hypothetical model was constructed summarizing our current knowledge and understanding of the various mechanisms.

Plasma levels of insulin-like growth factor binding protein-4 (IGFBP-4) under normal and pathological conditions.

OBJECTIVE: Insulin-like growth factor binding protein-4 (IGFBP-4) belongs to a family of six structurally related IGF-binding proteins that are involved in the modulation of the biological effects of the IGFs. In order to obtain more insight into the clinical significance and regulation of IGFBP-4 in vivo we determined the levels of this protein by a specific radioimmunoassay in the human circulation under normal and various pathological conditions. DESIGN AND PATIENTS: Selected human biological fluids and plasma samples from 804 normal healthy males and females, ranging from 0 to 78 years of age, were analysed. In addition, plasma samples from patients with several disorders (i.e. hypothyroidism, hyperthyroidism, GH-deficiency, acromegaly, cancer, chronic renal failure corticosteroid-treatment) were investigated. MEASUREMENTS: A specific RIA for hIGFBP-4 was developed, using a rabbit polyclonal antibody raised against a synthetic peptide containing amino acids 80-103 of the mature hIGFBP-4 sequence. RESULTS: In normal individuals circulating IGFBP-4 levels in males did not change with age. For females the values tended to increase slightly in older age. Overall, the mean +/- SD for males and females (189 +/- 83 microg/l and 193 +/- 72 microg/l, respectively) were not different. Normative range values of IGFBP-4 correlated weakly with those of IGF-II (r = 0.31, P < 0.001). Neither hypothyroidism nor hyperthyroidism appeared to influence circulating IGFBP-4 levels since the levels were within the normal range. Both GH status and pharmacological doses of glucocorticoids, as employed in various chronic diseases, did not seriously affect plasma IGFBP-4 either. Under conditions with increased circulating PTH levels, i.e. dialysed adult patients with chronic renal failure (CRF) and subjects with hyperparathyroidism, a weak positive relationship was noted between the plasma contents of IGFBP-4 and PTH. An excess of IGFBP-4 was found in plasma of both nondialysed and dialysed prepubertal growth retarded children with chronic renal failure (CRF) (mean SDS: 10.75 and 5.78, respectively). IGFBP-4 levels were inversely related to glomerular filtration rate. Similar results were obtained for dialysed adults with CRF. In a group of CRF children who had undergone renal transplantation, circulating IGFBP-4 levels were markedly lower (mean SDS: 3.75). There was no evidence for an increased secretion of IGFBP-4 in the circulation of most of the cancer patients with solid tumours. Several children with acute lymphoblastic leukaemia, however, showed elevated plasma IGFBP-4 levels (mean SDS: 1.27). The presence of IGFBP-4 could also be demonstrated in other human biological fluids. The highest amounts were found in amniotic fluid (391-717 microg/l) and follicular fluid (249-500 microg/l). CONCLUSIONS: Measurement of plasma IGFBP-4 has been shown so far to be of minor clinical relevance. However, the results indicate that different concentration gradients between plasma and various other body fluids may exist. Therefore, it may well be that certain pathophysiological stimuli induce significant alterations in the local turnover rate of IGFBP-4 but that they are not reflected by changes in the circulating levels. The possibility of quantifying IGFBP-4 by RIA will facilitate further in vitro and in vivo studies on its regulation and function in humans.

Insulin-like growth factors and leucine kinetics during exercise training in children with cystic fibrosis.

BACKGROUND: Little is known about the metabolic effects of exercise training in children with cystic fibrosis. The hypothesis for the current study was that in patients with declining clinical status, exercise increases circulating insulin-like growth factors (IGFs) and improves protein kinetics. METHODS: This was a prospective intervention study in 10 children with cystic fibrosis who participated in a structured isoenergetic exercise (cycling) training program for 3 months. Measurements of IGFs, protein kinetics (using intravenous [13C]-1-leucine tracer infusions) and nutritional balance studies were conducted at baseline and after 3 months. RESULTS: Standard deviation scores of plasma IGF-I, IGF-II, and IGF binding protein (BP)-3 were all decreased at baseline (mean +/- SE: -2.0+/-0.2, -2.0+/-0.2. -0.6+/-0.2, respectively). IGF-I and IGF-II concentrations were significantly higher after exercise training (standard deviation scores -1.4+/-0.3 and -1.3 +/-0. 1, respectively; compared with baseline: one-tailed t-test P = 0.03 and 0.002). The standard deviation score of the IGF-I/IGF BP-3 ratio, an indicator of free IGF-I in the circulation, normalized during exercise training (0.0+/-0.6 vs. -1.3+/-0.2 SD units at baseline, one-tailed t-test P = 0.04). There was no significant difference in protein intake and fasting protein breakdown, oxidation, and protein synthesis or in energy balance and fat absorption. CONCLUSIONS: These results show that isoenergetic exercise training can be safely recommended to patients with cystic fibrosis. It provides a positive anabolic stimulus to IGF status but is not sufficient to adequately augment protein accretion in patients with diminished nutritional status.

Dehydroepiandrosterone sulfate treatment for atrichia pubis.

OBJECTIVE: To evaluate the efficacy of oral dehydroepiandrosterone sulfate (DHEAS) treatment for atrichia pubis in female adolescents. STUDY DESIGN: Two XY female adolescents with 17-hydroxylase deficiency and 2 XX females with panhypopituitarism presenting with atrichia pubis were treated with a daily dosage of DHEAS 10 mg/m2 body surface in addition to their regular substitution therapy. The dosage was increased according to clinical response. Pubic hair stages, growth and serum DHEAS were evaluated and in 1 case also serum IGFs and IGFBPs. RESULTS: A dosage of 10 mg/m2 for 1 year led to serum DHEAS levels at the lower limit of the normal range. 15 mg/m2 was needed to achieve pubic hair stage 4-5 and axillary hair in patients with 17-hydroxylase deficiency. In panhypopituitarism, pubic hair developed at a slower pace and reached stage 4 on a dosage of 25-30 mg/m2. Baseline serum IGF-I SDS was -0.67 and did not change on the initial dosage of DHEAS, in combination with submaximal estrogen substitution (10 microg ethinyl estradiol). On the combination of 15 mg/m2 DHEAS and full estrogen substitution, IGF-I SDS increased to an average of -0.15. IGFBP-3 SDS increased from 1.4 to a mean of 2.6 in the first year, and went back to 1.4 in the second year. IGFBP-6 SDS was low at baseline (-2.5) and rose to -1.9 and -1.7 IGF-II and IGFBP-1 showed an irregular pattern. CONCLUSIONS: Oral administration of DHEAS in a dosage of 15 mg/m2 o.d. is an efficacious treatment for atrichia pubis. For females with a panhypopituitarism a higher dosage appears needed. Given this and other biological actions of DHEAS, substitution therapy with DHEAS or DHEA to females with adrenal androgen deficiency appears rational.

A model for regulation of the Mg(2+)-stimulated acto-myosin-ATPase activity: inhibition of the formation of actin-myosin complex and the Mg( 2+)-stimulated acto-myosin-ATPase activity by IMP and AMP.

Previously, we showed that the decrease in force output during continuous isometric contractions in rat skeletal muscle was related to an increase in the concentration of IMP. In this paper we report on additional experiments in which the effect of IMP on the Mg(2+)-stimulated acto-myosin-ATPase activity of isolated actin and myosin is measured at 35 degrees C. The results show that 1) the binding of actin to myosin is co-operative (Hill coefficient = 3.82); 2) in the presence of IMP or AMP the Mg(2+)-stimulated acto-myosin-ATPase activity is inhibited up to 60% at 10 mM; 3) in the presence of IMP or AMP not only the Mg(2+)-stimulated acto-myosin-ATPase activity decreases, but also K(50). From these results we conclude that IMP and AMP may be considered as uncompetitive inhibitors. Our results suggest that IMP and AMP can prevent an 'energy crisis' during exhaustive exercise of short duration by down-regulating the contractile machinery.

Circulating levels of human insulin-like growth factor binding protein-6 (IGFBP-6) in health and disease as determined by radioimmunoassay.

OBJECTIVE: Insulin-like growth factor binding protein-6 (IGFBP-6) is a relatively unknown member of a family of six specific structurally related IGF binding proteins which are involved in the modulation of the biological effects of the IGFs. A distinctive property of IGFBP-6 is its preferential affinity for IGF-II relative to IGF-I. In order to obtain more insight into the clinical significance and regulation of circulating levels of IGFBP-6 we developed a specific radioimmunoassay (RIA) for this protein. DESIGN AND PATIENTS: Selected human biological fluids and plasma from 847 normal subjects were analysed. In addition, plasma samples from patients with different disorders (i.e. GH-deficiency, acromegaly, cancer, corticosteroid-treated children suffering from different kinds of severe illness and chronic renal failure) were investigated. MEASUREMENTS: The IGFBP-6 assay is competitive, utilizing a rabbit polyclonal antibody raised against a synthetic peptide comprising amino acids 90-118 of the hIGFBP-6 sequence and an additional tyrosine residue. It is calibrated against recombinant human (rh)IGFBP-6. The 125I tracer is prepared by iodination of the synthetic peptide. There is no significant cross-reactivity with other IGFBPs and no interference with the IGFs. RESULTS: Extensive normative range values for IGFBP-6 were determined using 847 plasma samples from normal males and females, ranging from 0 to 75 years of age. IGFBP-6 levels increased gradually (about two-fold) with age. In childhood the plasma levels of IGFBP-6 in females tended to be slightly higher than those for males. For the adult population the reverse was observed. Overall, the mean +/- SD value for males was higher than that for females (149 +/- 57 vs. 139 +/- 45 micrograms/l, P < 0.004). GH status did not appear to influence IGFBP-6 level since normal levels were found for both untreated acromegalic patients and GH-deficient subjects. GH treatment of the latter group of patients did not alter IGFBP-6 in plasma. Pharmacological doses of glucocorticosteroids affected circulating IGFBP-6 levels only slightly. IGFBP-6 levels in plasma samples derived both from children with acute lymphoblastic leukaemia and from patients with various types of solid neoplasms were generally within the normal range. In contrast, plasma samples from four of six patients with non-islet cell tumour induced hypoglycaemia (NICTH) showed elevated concentrations of IGFBP-6 (SDS > 2.9). An excess of IGFBP-6 was also found in plasma of both dialysed and non-dialysed prepubertal growth retarded children with chronic renal failure (CRF) (mean SDS: 23.0 and 9.3, respectively). IGFBP-6 levels were inversely correlated with glomerular filtration rate. In a group of CRF patients who underwent renal transplantation circulating IGFBP-6 levels were markedly lower (mean SDS: 4.6). The presence of IGFBP-6 could also be demonstrated in several other human biological fluids. Low amounts were detected in saliva (3-12 micrograms/l) and breast milk (6-45 micrograms/l) while the levels in amniotic fluid and follicular fluid were comparable with those determined in normal plasma. The IGFBP-6 content of cerebrospinal fluid (CSF) ranged between 25 and 87 micrograms/l, which is rather high in relation to the relatively low concentration of total protein in this body fluid. CONCLUSIONS: Measurements of IGFBP-6 have been shown so far to be of relatively minor clinical relevance. The exceptions are chronic renal failure patients and subjects with large tumours and non-islet cell tumour induced hypoglycaemia who may exhibit elevated circulating levels of this IGFBP. The physiological significance of this observation remains to be elucidated. The possibility of quantifying IGFBP-6 by specific RIA will facilitate further in vitro and in vivo studies of its regulation and function in man.

Hypoglycaemia associated with the production of insulin-like growth factor II and insulin-like growth factor binding protein 6 by a haemangiopericytoma.

Non-islet-cell tumour-induced hypoglycaemia (NICTH) is, in most cases, attributable to tumour production of insulin-like growth factor II (IGF-II). Tumour-derived IGF-II has a higher than normal molecular weight (big 'IGF-II') and an impaired ability to form the normal ternary 150 kD complex with IGF binding protein-3 (IGFBP-3) and the acid-labile subunit (ALS). Consequently, tumoral IGF-II circulates mainly in smaller binary complexes which have a higher bioavailability than the ternary complex. We had the opportunity to analyze IGFs and IGF-related factors in both pre- and post-operative blood, tumour tissue and tumour cyst fluid from a patient with a disseminated haemangiopericytoma and severe hypoglycaemia. In addition, the effect of serum and tumour cyst fluid on autophosphorylation of the insulin receptor was examined. Patient serum contained low levels of IGF-I, IGFBP-3 and ALS, while the concentrations of IGFBP-2 and IGFBP-6 were markedly elevated. The total level of circulating IGF-II was within the normal range, but Biogel P-60 gel filtration of patient serum revealed that 77% of the IGF-II was present in high molecular weight forms (normal: 10-15%), which decreased to 53% after partial removal of the tumour. Most of the IGF-II immunoreactivity in pre- and post-operative patient serum was associated with 50-60 kD complexes with only a minimal contribution (<10%) from the 150 kD complex. Tumour cyst fluid contained excessive amounts of both big IGF-II and IGFBP-6. Northern blot analysis of total mRNA isolated from the tumour demonstrated high expression of the IGF-II gene and abundant 1.1 kb IGFBP-6 transcript, while the genes encoding IGFBP-3, -4 and -5 were only weakly expressed and mRNA of IGFBP-1, -2 and IGF-I could not be detected. mRNAs for the IGF type II receptor could be easily demonstrated, whereas those for the insulin- and IGF type I receptor were hardly detectable. In contrast to patient serum tumour cyst fluid strongly stimulated the insulin receptor in vitro. The present study suggests an important role of the simultaneous production of IGF-II and IGFBP-6 in the pathophysiology of tumour-induced hypoglycaemia.

Insulin-like growth factors (IGF-I, free IGF-I and IGF-II) and insulin-like growth factor binding proteins (IGFBP-2, IGFBP-3, IGFBP-6, and ALS) in blood circulation.

Insulin-like growth factors (IGFs) and IGF binding proteins (IGFBPs) play an important role in cell growth and differentiation. Clinical and epidemiological studies have indicated that measuring IGFs and IGFBPs in blood has potential implications in assessing growth-related abnormalities and risks of certain types of cancer. To facilitate the application, we reported a large collection of reference ranges of IGFs and IGFBPs in normal population and evaluations of these molecules in serum and plasma as well as the impact of freeze-thaw cycles on the measurement. IGF-I, IGFBP-3 andALS showed a similar pattern of change associated with age. Levels of these molecules were low at birth and increased with age through puberty. After puberty the levels declined slowly with age. Overall, IGF-I, IGFBP-3 and ALS were slightly higher in females than in males. Free IGF-I accounted for about 1% of the total IGF-I and its variation with age was similar to total IGF-I. IGF-II levels were also increased with age from birth to puberty, but became stable after puberty. There was little difference in IGF-II levels between genders. IGFBP-2 levels declined with age from birth to puberty. Levels of IGFBP-6 in contrast were increased with age. These IGF binding proteins were higher in males than in females. IGFs, IGFBP-3 and ALS were 5-10% higher in serum than in plasma. IGFBP-2 and IGFBP-6 differed substantially between serum and plasma. Freeze-thaw treatment up to five cycles had little impact on plasma levels of IGFs and IGFBP-3. Our observations suggest that levels of IGFs and their binding proteins are varied with age, gender, and types of specimen and that these variations need to be taken into consideration when IGFs and their binding proteins are utilized in clinic and research.

Non-islet-cell tumour induced hypoglycaemia: a case report and review of literature.

A 54-year-old man presented with a poorly differentiated adenocarcinoma of the rectum with multiple metastases to the liver. During hospitalization the patient developed periods of hypoglycaemia due to production of "big" IGF-II by the tumour. Possible pathophysiological mechanisms of non-islet-cell tumour-induced hypoglycaemia are discussed.