Serum IGF-I measured by four different immunoassays in patients with adult GH deficiency or acromegaly and in a control population

Challenges of insulin-like growth factor-1 testing

Insulin-like growth factor 1 (IGF-1), primarily synthesized in the liver, was initially discovered due to its capacity to replicate the metabolic effects of insulin. Subsequently, it emerged as a key regulator of the actions of growth hormone (GH), managing critical processes like cell proliferation, differentiation, and apoptosis. Notably, IGF-1 displays a longer half-life compared to GH, making it less susceptible to factors that may affect GH concentrations. Consequently, the measurement of IGF-1 proves to be more specific and sensitive when diagnosing conditions such as acromegaly or GH deficiency. The recognition of the existence of IGFBPs and their potential to interfere with IGF-1 immunoassays urged the implementation of various techniques to moderate this issue and provide accurate IGF-1 results. Additionally, in response to the limitations associated with IGF-1 immunoassays and the occurrence of discordant IGF-1 results, modern mass spectrometric methods were developed to facilitate the quantification of IGF-1 levels. Taking advantage of their ability to minimize the interference caused by IGF-1 variants, mass spectrometric methods offer the capacity to deliver robust, reliable, and accurate IGF-1 results, relying on the precision of mass measurements. This also enables the potential detection of pathogenic mutations through protein sequence analysis. However, despite the analytical challenges, the discordance in IGF-1 reference intervals can be attributed to a multitude of factors, potentially leading to distinct interpretations of results. The establishment of reference intervals for each assay is a demanding task, and it requires nationwide multicenter collaboration among laboratorians, clinicians, and assay manufacturers to achieve this common goal in a cost-effective and resource-efficient manner. In this comprehensive review, we examine the challenges associated with the standardization of IGF-1 measurement methods, the minimization of pre-analytical factors, and the harmonization of reference intervals. Particular emphasis will be placed on the development of IGF-1 measurement techniques using "top-down" or "bottom-up" mass spectrometric methods.

Proposed reference intervals of serum insulin-like growth factor-1 (IGF-1) levels in older Japanese populations

Measurements of serum insulin-like growth factor 1 (IGF-1) levels are useful surrogate markers for the diagnosis and management of patients with growth hormone-related disorders. We have previously published normative data of serum IGF-1 levels for the Japanese population aged 0-77 years by combining and analyzing previously reported references, which were separately and independently constructed, to properly reflect data in the transition period. Although the reference is widely used in both clinical and research settings, the reference did not include data for those aged >77 years, raising the question of how we would evaluate patients over those ages. In this study, we extended the age- and sex-specific reference ranges of serum IGF-1 levels to the age of 80 years by reanalyzing combined data on serum IGF-1 levels from previously published references. Based on our results, we proposed that individuals aged >80 years can be evaluated using the references set at the age of 80 years. However, our proposal was based on a very limited number of participants. Therefore, physicians should exercise caution when interpreting IGF-1 standard deviation scores for those aged >80 years because they are not exactly correct but acceptable.

The impact of different calibration matrices on the determination of insulin-like growth factor 1 by high-resolution-LC-MS in acromegalic and growth hormone deficient patients

OBJECTIVES

Calibration is an important source of variability in liquid chromatography mass spectrometry (LC-MS) methods for insulin-like growth factor 1 (IGF-1). This study investigated the impact of different calibrator matrices on IGF-1 measurements by LC-MS. Moreover, the comparability of immunoassays and LC-MS was assessed.

DESIGN & METHODS

Calibrators from 12.5 to 2009 ng/ml were prepared by spiking WHO international Standard (ID 02/254 NIBSC, UK) into the following matrices: native human plasma, fresh charcoal-treated human plasma (FCTHP), old charcoal-treated human plasma, deionized water, bovine serum albumin (BSA), and rat plasma (RP). A validated in-house LC-MS method was calibrated repeatedly with these calibrators. Then, serum samples from 197 growth hormone excess and deficiency patients were analysed with each calibration.

RESULTS

The seven calibration curves had different slopes leading to markedly different patient results. The largest differences in IGF-1 concentration from the median (interquartile range) was observed with the calibrator in water and the calibrator in RP (336.4 [279.6-417.0] vs. 112.5 [71.2-171.2], p < 0.001). The smallest difference was observed with calibrators in FCTHP and BSA (141.8 [102.0-198.5] vs. 127.9 [86.9-186.0], p < 0.049). Compared to LC-MS with calibrators in FCTHP, immunoassays showed relevant proportional bias (range: -43% to -68%), constant bias (range: 22.84 to 57.29 ng/ml) and pronounced scatter. Comparing the immunoassays with each other revealed proportional bias of up to 24%.

CONCLUSIONS

The calibrator matrix is critical for the measurement of IGF-1 by LC-MS. Regardless of the calibrator matrix, LC-MS shows poor agreement with immunoassays. Also, the agreement between different immunoassays is variable.

Reference values for IGF-I serum concentration in an adult population: use of the VARIETE cohort for two new immunoassays

OBJECTIVE

Measurement of IGF-I is important in the management of patients with growth hormone disorders. Here we aim to establish normative data for two new IGF-I assay kits based on a large random sample of the French general adult population.

SUBJECTS AND METHODS

We measured IGF-I in 911 healthy adults (18-90 years) with two immunoassays (ROCHE Elecsys® and IMMULITE-2000 calibrated against the new IS 02/2547). We compared the data with those of the six immunoassays (iSYS, LIAISON XL, IMMULITE-2000 calibrated against the first IS 87/518, IGF-I RIACT, Mediagnost ELISA, and Mediagnost RIA) that we reported previously. The pairwise concordance among the eight assays was assessed with Bland-Altman plots for both the IGF-1 raw data and the standard deviation scores (SDS), as well as with the percentage of observed agreement and the weighted Kappa coefficient for categorizing IGF-I SDS (ClinicalTrials.gov Identifier: NCT01831648).

RESULTS

The normative data included the range of values (2.5-97.5 percentiles) given by the two new IGF-I assays according to age group and sex. A formula for the SDS calculation is provided. As for the previous six assays, the lower limits of the reference intervals of the two new assays were similar, but the upper limits varied markedly. The pairwise concordances were only moderate (kappa 0.57).

CONCLUSIONS

Data obtained for these two new IGF-I immunoassays confirm that despite being obtained in the same large healthy population, the reference intervals of the eight commercial IGF-1 assay kits showed noteworthy differences. The agreement among the various methods was moderate to good.

An antibody-free LC-MS/MS method for the quantification of intact insulin-like growth factors 1 and 2 in human plasma

Insulin-like growth factors 1 and 2 (IGF-1 and IGF-2) are important biomarkers in research and diagnosis of growth disorders. Quantitative analysis is performed using various ligand-binding assays or enzymatic digestion LC-MS/MS methods, whose widespread adoption is hampered by time-consuming sample preparation procedures. We present a simple and fast antibody-free LC-MS/MS method for the quantification of intact IGF-1 and IGF-2 in human plasma. The method requires 50 μL of plasma and uses fully ¹⁵N-labelled IGF-1 as internal standard. It features trifluoroethanol (TFE)-based IGF/IGF-binding protein complex dissociation and a two-step selective protein precipitation workflow, using 5% acetic acid in 80/20 acetone/acetonitrile (precipitation 1) and ice-cold ethanol (precipitation 2). Detection of intact IGF-1 and IGF-2 is performed by means of a Waters XEVO TQ-S triple quadrupole mass spectrometer in positive electrospray ionisation (ESI+) mode. Lower limits of quantification were 5.9 ng/mL for IGF-1 and 8.4 ng/mL for IGF-2. Intra-assay imprecision was below 4.5% and inter-assay imprecision was below 5.8% for both analytes. An excellent correlation was found between nominal and measured concentrations of the WHO reference standard for IGF-1. Comparison with the IDS-iSYS IGF-1 immunoassay showed good correlation (R² > 0.97), although a significant bias was observed with the immunoassay giving substantially higher concentrations. The LC-MS/MS method described here allows for reliable and simultaneous quantification of IGF-1 and IGF-2 in plasma, without the need for enzymatic digestion. The method can be readily implemented in clinical mass spectrometry laboratories and has the potential to be adapted for the analysis of different similarly sized peptide hormones.

A quantitative LC-MS/MS method for insulin-like growth factor 1 in human plasma

BACKGROUND

Insulin-like growth factor 1 (IGF1) is a biomarker with various applications in medicine and also in doping control.

METHODS

A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed that employs 15N-IGF1 as an internal standard. The method features urea-based IGF1/IGFBP-complex dissociation which is directly followed by tryptic digestion. Following solid-phase extraction (SPE) sample clean-up of the digest, IGF1 is detected by means of two signature peptides that enable quantification of total IGF1 as well as discrimination between IGF1 proteoforms with 'native' and modified or extended N-terminal sequences.

RESULTS

Our method is capable of measuring plasma IGF1 concentrations over the clinically relevant range of 10-1000 ng/mL and was validated according to regulatory guidelines. Comparison with the IDS-iSYS IGF1 immunoassay revealed good correlation (R2>0.97) and no proportional bias between both assays was observed after normalizing the results against the WHO reference standard for IGF1 (02/254). Evaluation of several commercially available IGF1 preparations showed varying responses which were due to inconsistencies in purity and absolute amount of IGF1 present in these products.

CONCLUSIONS

Our LC-MS/MS method introduces urea-based dissociation of IGF1/IGFBP-complexes to enable reliable quantification of IGF1 in plasma. Furthermore, the method is able to detect clinically relevant IGF1 levels without an enrichment procedure at the protein-level and thereby minimizes the risk of losing IGF1 proteoforms during sample preparation.

Insulin-Like Growth Factor-1 in Acute Ischemic Stroke

Background

Cerebrovascular ischemic stroke is highly prevalent in the general population and is considered one of the frequent causes of mortality and disability. Insulin-like growth factor-1 (IGF-1) is recognized as an important neuro-protective factor against cerebral vascular ischemic insult.

Aim of the work

To study the relationship between serum IGF-1 levels and acute ischemic stroke (AIS) in the Egyptian population.

Patients and methods

Two hundred patients with AIS (within the first 24 h) were subjected to full neurological examination, assessment of stroke severity using National Institute of Health Stroke Scale (NIHSS) and measurement of serum IGF-1 levels. The control group included 100 subjects matched for age, gender, and conventional vascular risk factors.

Results

Serum IGF-1 levels were significantly reduced in cases of first AIS compared to control group. A reduced serum IGF-1 level was an independent risk factor for ischemic stroke with cut off value less than 148.3 ng/ml associated with increased AIS risk.

Conclusion

Lower IGF-1 levels are significantly related to risk of ischemic stroke occurrence, independent from other conventional risk factors in the Egyptian population.

Discordance between mass spectrometry and immunometric IGF-1 assay in pituitary disease: a prospective study

PURPOSE

Measuring IGF-1, a biomarker for GH activity, is critical to evaluating disordered hypothalamic-pituitary GH axis. Inconsistent IGF-1 measurements among different immunoassays are well documented. We switched from Immulite 2000 immunoassay to narrow-mass-extraction, high-resolution liquid chromatography mass-spectrometry (LC-MS) compliant with recent consensus recommendations on assay standardization. Comparability of these two assays in patients with pituitary disease in a clinical practice setting is not known. We sought to compare IGF-1 levels on Immulite 2000 and LC-MS in samples from naïve and treated patients with secretory and non-secretory pituitary masses.

METHODS

We prospectively collected serum samples from 101 patients treated at the Cedars-Sinai Pituitary Center between February 2012 and March 2014. We intentionally recruited more patients with acromegaly or GH deficiency to ensure a clinically representative cohort. Samples were classified as in or out of the respective reference ranges. Bland-Altman analysis was used to assess agreement between assays.

RESULTS

Twenty-four percent of samples were classified differently as below, in, or above range. Agreement between the assays was poor overall, with a significant bias for immunoassay reporting higher values than LC-MS. This pattern was also observed in patients with acromegaly and those with ≥ 2 pituitary hormone deficiencies.

CONCLUSIONS

IGF-1 results may differ after switching from an older immunoassay to a consensus-compliant assay such as LC-MS. Clinicians should consider the potential impact of assay switching before altering treatment due to discrepant results, particularly in patients monitored over time, such as those with acromegaly and GH deficiency.

Agreement between circulating IGF-I, IGFBP-1 and IGFBP-3 levels measured by current assays versus unavailable assays previously used in epidemiological studies

OBJECTIVE

Levels of insulin-like growth factor (IGF) proteins are associated with the risk of cancer and mortality. IGF assays produced by Diagnostic Systems Laboratories (DSL) were widely used in epidemiological studies, were not calibrated against recommended standards and are no longer commercially available.

DESIGN

In a split sample study among 1471 adults participating in the Cardiovascular Health Study, we compared values obtained using DSL assays with alternative assays for serum IGF-I (Immunodiagnostic Systems, IDS), IGFBP-1 (American Laboratory Products Company, ALPCO) and IGFBP-3 (IDS).

RESULTS

Results were compared using kernel density estimation plots, quartile analysis with weighted kappa statistics and linear regression models to assess the concordance of data from the different assays. Participants had a mean age of 77years. Results between alternative assays were strongly correlated (IGF-I, r=0.93 for DSL versus IDS; log-IGFBP-1, r=0.90 for DSL versus ALPCO; IGFBP-3, r=0.92 for DSL versus IDS). Cross tabulations showed that participants were usually in the same quartile categories regardless of the assay used (overall agreement, 74% for IGF-I, 64% for IGFBP-1, 71% for IGFBP-3). Weighted kappa also showed substantial agreement between assays (kw, 0.78 for IGF-I, 0.69 for IGFBP-1, 0.76 for IGFBP-3). Regressions of levels obtained with DSL assays (denoted X) to alternative assays were, IGF-I: 0.52X+15.2ng/ml, log-IGFBP-1: 1.01X-1.73ng/ml IGFBP-3: 0.87X+791.1ng/ml. Serum values of IGF-I, IGFBP-1 and IGFBP-3 measured using alternative assays are moderately correlated.

CONCLUSIONS

Care is needed in the interpretation of data sets involving IGF analytes if assay methodologies are not uniform.

Reference ranges for an automated chemiluminescent assay for serum insulin-like growth factor I (IGF-I) in a large population of healthy adults from Buenos Aires

PURPOSE

Insulin-like growth factor I (IGF-I) represents an essential tool in the diagnostic work-up and in the monitoring of treatment efficacy for somatotrophic axis disorders both in children and adults. A large number of factors including, but not limited to, age, sex and weight as well as analytical variables influence IGF-I serum levels; therefore, reliable normative data are essential for a correct interpretation of results. The aim of the present study was to establish reference range values for serum IGF-I, in a large population of healthy adults from Buenos Aires city.

METHODS

The study included serum samples from 1044 healthy subjects aged 21-87 years (423 females and 621 males) divided into groups by sex at 5-year intervals from 21 to >75 years. Serum IGF-I concentrations were determined by a fully automated two-site, solid-phase, enzyme-labeled chemiluminescent immunometric assay (Immulite 2000, Siemens Healthcare Diagnostics). IGF-BP interferences are circumvented by blocking IGF-BP binding sites with excess IGF-II in the on-board predilution step.

RESULTS

Results show the age dependence of circulating IGF-I levels, with a smooth and steady decrease in levels with age. No sex differences were found in subjects >26 years; however, in the group aged 21-25 years, IGF-I levels were significantly higher in females. In conclusion, this study provides age- and gender-adjusted normal reference ranges for IGF-I levels obtained with an automated immunometric chemiluminescent assay Immulite 2000 in healthy adult subjects.

The association between IGF-I/IGFBP-3 and subclinical end points: epidemiology faces the limits

BACKGROUND

The variation in laboratory measurements represents a challenge in clinical practice and epidemiological research. The use of different analytical platforms might have led to different results, which were often discussed in the interpretation of conflicting results. We aim to study the impact of two different IGF-I and IGF binding protein 3 assays on published epidemiological studies.

METHODS

We compared epidemiological results based on the previous gold standard Nichols Advantage, which is no longer available, with these based on the IDS-iSYS assay. The latter follows the recently proposed Keswick criteria. We reinvestigated published association studies between IGF-I or IGF binding protein 3 and anthropometry, subclinical cardiovascular diseases including intima-media thickness or left ventricular mass index, and hard end points like mortality and single-nucleotide polymorphisms of our genome-wide association study in the Study of Health in Pomerania.

RESULTS

We demonstrated that there are significant differences in the associations of IGF-I measured by the Nichols or IDS-iSYS assay and subclinical outcomes including intima-media thickness and left ventricular mass index. However, concerning hard outcomes like mortality or single-nucleotide polymorphisms, our analyses revealed similar results with comparable regression estimates.

CONCLUSION

With our study we queried not only the accuracy of measurement but also the effect of different methods on study results. The establishment of laboratory standards like the Keswick criteria should be enforced to allow reliable comparisons of different methods and thus clinical and epidemiological studies. Single-center studies have to be interpreted carefully. Moreover, to assure the reliability of studies, their results should be replicated in a meta-analysis, and a generated hypothesis by epidemiology should be proven by intervention studies.

Insulin-like growth factor-1 as a prognostic marker in patients with acute ischemic stroke

Objective

Insulin-like growth factor-1 (IGF-1) has been associated with cardiovascular risk factors and atherosclerosis. The aim of the present study was to evaluate the prognostic value of IGF-1 levels in patients with acute ischemic stroke (AIS).

Methods

All patients with first-ever AIS from August 1, 2012 to August 31, 2013 were recruited to participate in the study. Clinical data were collected. The National Institutes of Health Stroke Scale (NIHSS) score was assessed on admission blinded to serum IGF-1 levels. For the assessment of functional outcome at 90 days Modified Rankin Scale (mRS) was used. On admission, serum IGF-1 levels were determined by chemiluminescence immunoassay. The influence of IGF-1 levels on functional outcome and death was assessed by multivariate logistic regression analysis.

Results

Patients with an unfavorable outcomes and non-survivors had significantly decreased serum IGF-1 levels on admission (P<0.0001 for both). IGF-1 was an independent prognostic marker of functional outcome and death [odds ratio 0.89 (0.84–0.93) and 0.90 (0.84–0.95), respectively, P<0.0001 for both, adjusted for age, NIHSS score and other predictors] in patients with ischemic stroke. Serum IGF-1 levels ≤130 ng/mL was as an value indicator for unfavorable functional outcome (OR 3.31, 95% CI:1.87–5.62; P<0.0001), after adjusting for other significant confounders.

Conclusions

We reported a significant association between low serum IGF-1 levels and unfavorable functional outcome and death.

The relationship between serum insulin-like growth factor I levels and ischemic stroke risk

Objective

The aim of the study was to assess the relationship between insulin-like growth factor I (IGF-I) serum levels and acute ischemic stroke (AIS) in a Chinese population.

Methods

All consecutive patients with first-ever AIS from August 1, 2011 to July 31, 2013 were recruited to participate in the study. The control group comprised 200 subjects matched for age, gender, and conventional vascular risk factors. IGF-I serum levels were determined by chemiluminescence immunoassay. The National Institutes of Health Stroke Scale (NIHSS) score was assessed on admission blinded to serum IGF-I levels.

Results

The median serum IGF-1 levels were significantly (P = 0.011) lower in AIS patients (129; IQR, 109–153 ng/mL) compared with control cases (140; IQR, 125–159 ng/mL). We found that an increased risk of AIS was associated with IGF-I levels ≤135 ng/mL (unadjusted OR: 4.17; 95% CI: 2.52–6.89; P = 0.000). This relationship was confirmed in the dose-response model. In multivariate analysis, there was still an increased risk of AIS associated with IGF-I levels ≤135 ng/mL (OR: 2.16; 95% CI:1.33–3.52; P = 0.002) after adjusting for possible confounders.

Conclusion

Lower IGF-I levels are significantly related to risk of stroke, independent from other traditional and emerging risk factors, suggesting that they may play a role in the pathogenesis of AIS. Thus, strokes were more likely to occur in patients with low serum IGF-I levels in the Chinese population; further, post-ischemic IGF-I therapy may be beneficial for stroke.

Long-term changes in serum IGF-1 levels after successful surgical treatment of growth hormone-secreting pituitary adenoma

BACKGROUND

Successful treatment of acromegaly is known to normalize serum insulin-like growth factor 1 (IGF-1) levels within days after surgery. However, our clinical observations indicate that many cases of acromegaly show delayed normalization of serum IGF-1 levels after complete tumor resection.

OBJECTIVE

To study long-term changes of the serum IGF-1 levels in acromegalic patients for whom surgical treatment was thought to be successful.

METHODS

A retrospective observational study was performed with 46 acromegalic patients with no residual tumor on sellar magnetic resonance imaging, and a nadir growth hormone of less than 0.4 μg/L on a postoperative oral glucose tolerance test.

RESULTS

In all patients, serum IGF-1 levels returned to the normal reference values for age and sex during the observational period (12-132 months). The mean duration from the time of surgery until IGF-1 normalization was 10 months (range, 3 days-57 months). Twenty-seven patients (59%) reached normal IGF-1 ranges within 3 months of surgery, whereas 19 patients (41%) experienced delayed (>3 months) IGF-1 normalization. Eleven patients (24%) recovered normal IGF-1 levels 12 to 57 months after surgery. The possibility of delayed IGF-1 cure was increased 8.8-fold with an immediate postoperative IGF-1 level increase of 100 μg/L.

CONCLUSION

Satisfactory remission of acromegaly by IGF-1 criteria was delayed in a large proportion of acromegalic patients, especially those with high postoperative IGF-1 levels. Hence, additional treatment can be delayed in clinically stable acromegalic patients who show no evidence of residual tumors on postoperative magnetic resonance imaging and a normal growth hormone suppressive response to a glucose load.

Increased genome instability and oxidative DNA damage and their association with IGF-1 levels in patients with active acromegaly

OBJECTIVE

The objectives of this study were to assess cytokinesis-block micronucleus cytome (CBMN Cyt) assay parameters and also oxidative DNA damage in patients with active acromegaly and controls and to assess the relationship between age, serum insulin-like growth factor 1 (IGF-1) levels, pituitary adenoma diameters, 8-hydroxy-2'-deoxyguanosine (8-OHdG) levels and CBMN Cyt assay parameters in patients with active acromegaly.

DESIGN

The study population included 30 patients with active acromegaly and 30 age- and sex-matched healthy controls. CBMN Cyt assay parameters in peripheral blood lymphocytes of patients with active acromegaly and controls were evaluated and plasma 8-OHdG levels were measured.

RESULTS

Frequencies of micronucleus (MN), nucleoplasmic bridges (NPBs) and nuclear buds (NBUDs) in lymphocytes of patients with acromegaly were found to be significantly higher than those in controls (p<0.001, p<0.001, p<0.001, respectively). The frequencies of apoptotic and necrotic cells in lymphocytes of patients with acromegaly were found to be significantly higher than those in controls (p<0.001 and p<0.001 respectively). No statistically significant differences in the number of cells in metaphase, the number of bi-nucleated cells (M2), the number of tri-nucleated cells (M3), the number of tetra-nucleated cells (M4) and nuclear division index (NDI) values were observed between patients and controls (p>0.05). Plasma 8-OHdG (ng/ml) levels in patients with acromegaly were found to be significantly higher than those in controls (p<0.005). MN frequency in the lymphocytes of patients with acromegaly increased with elevated serum IGF-1 levels (p<0.05), whereas the number of NPBs and the frequency of apoptotic cells decreased with elevated serum IGF-1 levels (p<0.01 and p<0.05 respectively).

CONCLUSIONS

Both the increase in chromosomal/oxidative DNA damage and the positive association between MN frequency and serum IGF-1 levels may predict an increased risk of malignancy in acromegalic patients. Long-term follow-up of patients with acromegaly will be necessary to establish the degree of cancer risk in this population.

IGF1 modifications after bariatric surgery in morbidly obese patients: potential implications of nutritional status according to specific surgical technique

OBJECTIVES

IGF1 is decreased in morbidly obese (MO) patients and its changes after bariatric surgery weight loss (WL) are not well known. The aim of this study was to analyse IGF1 modifications in MO patients after WL and its relationship to ghrelin and to different types of surgeries.

DESIGN

Retrospective follow-up study at the University Medical Center.

METHODS

One hundred and nine MO patients (age 44.19.3, BMI 51.748.75KG/M(2)) were evaluated at baseline and 1 year after surgery: 28 sleeve gastrectomy (SG), 31 distal modified (m), and 50 ringed (r) Roux-en-Y gastric bypass (RYGBP) surgery. Changes in IGF1, IGFBP3, ratio IGF1:IGFBP3, and ghrelin were evaluated 1 year after surgery.

RESULTS

Baseline prevalence of low IGF1 (defined by s.d. IGF1<-2) was 22%, and %WL 1 year after surgery was 34.9±8.9%. There was a significant decrease in IGFBP3 in all the procedures, an increase in IGF1:IGFBP3 ratio in rRYGBP and SG, but total IGF1 only increased significantly in SG. Albumin concentrations decreased in mRYGBP, did not change in rRYGBP, but increased in SG after surgery. Total ghrelin concentrations increased after both RYGBPs and decreased after SG (P<0.05 in all cases). The prevalence of low IGF1 decreased in SG (28.6 vs 10.1%, P=0.03) and did not change in RYGPBP techniques. The %albumin change was the only dependent variable associated with the % total IGF1 change.

CONCLUSIONS

Recovery of low IGF1 after bariatric surgery was specifically related to the albumin modifications induced by surgery and was not related to ghrelin modifications.

Serum IGF-1 in the diagnosis of acromegaly and the profile of patients with elevated IGF-1 but normal glucose-suppressed growth hormone

OBJECTIVE

To report the utility of insulin-like growth factor-1 (IGF-1) as a single biomarker for establishing the diagnosis of acromegaly and to examine the clinical and biochemical profile of patients with an elevated IGF-1 in whom a diagnosis of acromegaly could not be confirmed by means of the oral glucose tolerance test (OGTT).

METHODS

Between the years 1999 and 2010, we identified 101 patients who underwent pituitary surgery and had histologically proven somatotroph adenomas (Group 1, Gr 1). We selected 149 patients with non-growth hormone (GH) secreting pituitary macroadenomas (Gr 2, n = 97) and microadenomas (Gr 3, n = 52) to serve as control subjects. In addition, we identified 34 patients with elevated IGF-1values in whom acromegaly could not subsequently be proven by the OGTT (Gr 4).

RESULTS

IGF-1 was elevated in all patients with acromegaly prior to therapy with a median (range) standard deviation score (SDS) of +9.52 (+2.34 to +9.2), compared to SDS -1.46 (-2.91 to +2.17) and -1.22 (-2.8 to +1.58) in Gr 2 and 3, respectively (P<0.001). IGF-1 SDS values were +3.28 (+2.05 to +6.1), and IGF-1 was less than twice the upper limit of normal in all patients in Gr 4. OGTT was performed in 51 of the 101 acromegalic patients. The nadir GH in these patients was 4.01 (0.2 to 46.7) in comparison with 0.2 (<0.05 to 0.6) in Gr 4 (P<0.001).

CONCLUSION

Elevated IGF-1 levels, alone, are sufficient to establish a diagnosis of acromegaly in the majority of clinically suspected cases. The OGTT may be useful to obtain corroborative evidence when there is modest elevation of IGF-1 with absent or equivocal clinical features.

Comparison of two immunoassays in the determination of IGF-I levels and its correlation with oral glucose tolerance test (OGTT) and with clinical symptoms in acromegalic patients

The aim of our study was to evaluate two different methodologies in IGF-I levels determination, its correlation with GH nadir in OGTT <1 and <0.4 ng/ml and with clinical symptoms in acromegalic patients. We analyzed 37 patients. Sixteen patients had not undergone any kind of treatment (Group 1). Twenty-one patients underwent surgery as primary treatment, and after that, some of them another kind of treatment (except pegvisomant) (Group 2). Serum IGF-I levels were measured by Immulite-1000 (IMM) and by an immunoradiometric assay (DSL) and, GH by immunochemiluminometric assay. IGF-I levels by IMM and by DSL showed a significant difference. When we analyzed in both groups the concordance by crosstabs-Kappa coefficients, between different parameters, GH nadir <1 and <0.4 ng/ml with IGF-I by DSL and IMM showed concordance in group 1, but in group 2 only GH nadir <1 and <0.4 ng/ml had a weak concordance with IGF-I by IMM. When we analyzed clinical symptoms in the patients and, GH nadir <1 and <0.4 ng/ml and IGF-I levels by both methodologies, more than 90% of clinically active patients had abnormal GH response or/and elevated IGF-I levels in group 1, but less than 70% in group 2. In the 8 patients under medical treatment, GH nadir was higher than 0.4 ng/ml in all patients, and IGF-I levels were elevated in 8/8 by DSL and in 6/8 by IMM. In conclusion, discrepant GH and IGF-I levels in the diagnosis and follow-up of patients with acromegaly requires consideration of many factors that influence these parameters.

IGF-I and IGFBP-3 before and after inpatient alcohol detoxification in alcohol-dependent subjects

Background

It is unclear whether alcohol detoxification has an effect on factors that are involved in growth, metabolic functions and cell proliferation. Alcohol abuse is associated with low IGF-I levels that tend to rise after alcohol withdrawal. There is a paucity of studies on the course of IGFBP-3 (the main binding protein for IGF-I) after alcohol detoxification.

Material/Methods

We prospectively assessed IGF-I and IGFBP-3 changes at the time of admission and after 4 to 6 weeks of detoxification in an inpatient alcohol detoxification facility in 118 alcohol-dependent subjects given a regular hospital diet. No participants dropped out of the study.

Results

Changes in IGF-I after alcohol detoxification showed a marked dimorphism in altered hepatic biochemistry upon admission, with a rise in those with normal liver enzymes upon admission (p=0.016, Kruskall-Wallis) and a drop in those with elevated liver enzymes upon admission (p=0.05); the latter was noted in subjects that had consumed alcohol close to the time of admission. Overall, however, IGF-I and IGFBP-3 were within normal limits for most subjects both upon admission and after alcohol detoxification; no significant differences were detected among the examined parameters in men vs. women, and there were no significant correlations of IGF-I, IGFBP-3 or the IGF-I/IGFBP-3 molar ratio with BMI or age.

Conclusions

Regardless of hepatic enzymes’ elevation, alcohol detoxification had overall slight effects on IGF-I and IGFBP-3.

Micronucleus evaluation in mitogen-stimulated lymphocytes of patients with acromegaly

Acromegaly is a syndrome characterized by a sustained elevation of circulating growth hormone and insulin-like growth factor-1 (IGF-1). Insulin-like growth factor-1 is a potent mitogen and has a role in the transformation of normal cells to malignant cells. This study aims to evaluate the spontaneous micronucleus (MN) frequency by using the cytokinesis-block MN assay to determine genetic damage in the lymphocytes of patients with acromegaly. The study was carried out in 20 patients who had active acromegaly and in 20 age- and sex-matched healthy controls. The MN values were measured in binucleated cells obtained from mitogen-stimulated lymphocytes of patients and control subjects. The distribution of binucleated cells with 1, 2, 3, or more MNs was also measured. We found significantly higher MN frequency values in the lymphocytes of acromegalic patients than in those of the control subjects (2.23 ± 0.68 vs 1.03 ± 0.54, P = .001). The MN frequency increased with increasing IGF-1 levels of acromegalic patients (P = .036, R = 0.47). We observed that the number of binucleated cells with 2 MNs was higher for the majority of patients with acromegaly than for control subjects. Furthermore, the receiver operating characteristic curve (area under the curve = 0.914, P < .0001) was calculated to assess the discriminative power of the MN frequency. Our results indicate that increased MN frequency in the lymphocytes of patients with acromegaly may reflect genomic instability and this increased MN frequency may be associated with elevated levels of circulating growth hormone and IGF-1.

Impact of different cut-off limits of peak GH after GHRH-arginine stimulatory test, single IGF1 measurement, or their combination in identifying adult patients with GH deficiency

OBJECTIVE

To evaluate the impact of different peak GH cut-off limits after GHRH-Arg test, IGF1 measurement, or their combination in identifying patients with GH deficit (GHD).

DESIGN AND PATIENTS

Totally, 894 normal subjects (used for determining IGF1 normative limits) and 302 patients with suspected GHD were included. Different peak GH cut-off limits (used by European (depending on body mass index (BMI)) or North American (4.1 μg/l) Endocrine Societies, by HypoCCs (2.5 μg/l), or with 95% specificity (based on BMI), Method 1, 2, 3, or 4 respectively) and IGF1 were considered.

METHODS

Peak GH after GHRH-Arg and IGF1.

RESULTS

Different peak GH cut-off limits recognized different proportions of GHD (range, 24.8-62.9%). Methods 1 and 2 with high sensitivity recognized a higher proportion (95.5 and 92.5% respectively) of GHD among patients with three (T) pituitary hormone deficits (HD), whereas Method 4 (with high specificity) identified 96.7% normal subjects among those without pituitary HD; on the contrary, Method 4 identified only 75% GHD among patients with THD, whereas Method 1 recognized a high proportion (40%) of GHD among subjects without HD. Of the total patients, 82% with THD and 84.5% without HD were recognized as GHD or normal respectively by IGF1. Among the remaining patients with THD and normal IGF1, 75% was recognized as GHD by Method 1; among patients without HD and abnormal IGF1, 87.5% was identified as normal by Method 4. Overall, combination of IGF1 and Method 1 or Method 4 identified 95.5% GHD among patients with THD and 98.1% normal subjects among those without HD.

CONCLUSIONS

Single peak GH cut-offs have limits to sharply differentiate GHD from normal subjects; IGF1 may be used for selecting patients to be submitted to the GHRH-Arg test; the peak GH cut-off limits to be used for identifying healthy or diseased patients depend mainly on the clinical context.

Normal values of serum IGF-1 in adults: results from a Brazilian population

OBJECTIVE

To determine the normal values of serum IGF-1 (Immulite 2000) in a Brazilian adult (21-70 years) population.

SUBJECTS AND METHODS

Healthy volunteers were divided into 10 groups according to age (5-year intervals), with 100 subjects (50 men and 50 women) per group. One-hundred participants were selected for repetition of the test after 12 weeks.

RESULTS

No difference in IGF-1 values was observed between men and women, but a progressive reduction of serum IGF-1 with age was seen. The reference values provided by the manufacturer of the assay, although discretely higher, were very close to the values found in this study. A second measurement of IGF-1 after 12 weeks revealed a variation < 20% in 99% of subjects.

CONCLUSIONS

This study established the reference range for IGF-1 determined with the Immulite 2000 assay for a large number of healthy Brazilian adults stratified according to age, and suggests that variations > 20% in IGF-1 levels within an interval of 12 weeks cannot be attributed to interassay variability.

Serum insulin-like growth factor-I and pro-collagen type III N-terminal peptide in adolescent elite athletes: implications for the detection of growth hormone abuse in sport

CONTEXT

A method based on two GH-dependent markers, IGF-I and pro-collagen type III N-terminal peptide (P-III-P), has been devised to detect exogenously administered GH. Because previous studies on the detection of GH abuse involved predominantly adult athletes, the method must be validated in adolescent athletes.

OBJECTIVE

The aim of the study was to examine serum IGF-I and P-III-P concentrations in elite adolescent athletes and to determine whether the method developed in adults is appropriate to detect GH abuse in this population.

DESIGN AND SETTING

We conducted a cross-sectional observational study at national sporting organization training events.

SUBJECTS

A total of 157 (85 males, 72 females) elite athletes between 12 and 20 yr of age participated in the study.

INTERVENTION

Serum IGF-I and P-III-P were each measured by two commercially available immunoassays. GH-2000 discriminant function scores were calculated.

RESULTS

Both IGF-I and P-III-P rose to a peak during adolescence, which was earlier in girls than in boys. All GH-2000 scores lay below the proposed cutoff limit of 3.7 (although some scores were close to this value), indicating that none of these athletes would be accused of GH doping if the GH-2000 discriminant formulae were used. The results between the two immunoassays for IGF-I and P-III-P were closely aligned.

CONCLUSIONS

The GH-2000 score rises in early adolescence, reaches a peak in athletes aged 13-16 yr, and then falls. We have found no evidence that the proposed GH-2000 score developed in adults would lead to an unacceptable rate of false-positive results in adolescent athletes, but caution may be required around the time of peak growth velocity.

Role of two nutritional hepatic markers (insulin-like growth factor 1 and transthyretin) in the clinical assessment and follow-up of acute intermittent porphyria patients

OBJECTIVE

Acute intermittent porphyria (AIP) is caused by a deficiency of hydroxymethylbilane synthase. Clinical manifestations are abdominal pain and neurovisceral symptoms, accompanied by overproduction of heme-precursors in the liver, which frequently remains long-lasting in AIP patients. We tested the hypothesis that this condition may be associated with alterations of hepatic proteins known to be either increased or decreased in serum according to diverse pathological conditions including malnutrition, inflammation or liver disease.

DESIGN

Serum proteins were analyzed in 26 biochemically active AIP patients that were classified according to the EPI (European Porphyria Initiative) guidelines as follows: (i) patients who presented a single acute attack having remained so far free of clinical symptoms; (ii) patients who present recurrent attacks or chronic symptoms associated with exacerbations of AIP.

RESULTS

Most of the serum proteins were within normal limits, however insulin-like growth factor 1 (IGF-1) was decreased in 53.8% of AIP patients (z-score = -2.86 +/- 0.37) and transthyretin (prealbumin) was found significantly decreased in 38.5% of them. The IGF-1 z-score was lower in group B versus group A patients (-2.66 vs. -1.43; P = 0.024). The coincident decrease of both IGF-1 and transthyretin was associated with worsening of the clinical condition.

CONCLUSIONS

This first study in humans suggests that the clinical expression AIP is associated with a state of under-nutrition and/or with hepatic inflammation due to the sustained accumulation of heme-precursors. We propose the use of both IGF-1 and transthyretin as biomarkers of disease morbidity/severity for the clinical follow-up of AIP patients.

Influence of gender on serum growth hormone, insulin-like growth factor-I and its binding protein-3 during aging

PURPOSE

The serum concentrations of insulin-like growth factors-I (IGF-I), insulin-like growth factor binding protein-3 (IGFBP-3) and growth hormone (GH) are related to body composition, function and metabolism, and are influenced by the aging process. This study was to investigate the influence of gender on serum concentrations of IGF-I, IGFBP-3 and GH in middle and old age subjects.

MATERIALS AND METHODS

Sixty healthy volunteers (male 35, female 25, 36-70 years) were divided into < or = 50 and > 50 years groups, based on gender. Women > 50 years were post-menopause. IGF-I, IGFBP-3, and GH were determined by immunoradiometric assay.

RESULTS

IGF-I was shown to be negatively correlated with age (women r = -0.62, p < 0.001; men r = -0.38, p < 0.05), whereas there was no correlation between IGF-I and GH values. Women > 50 years showed a significant reduction in IGF-I values than women < or = 50 years (p < 0.01). Women > 50 years showed smaller IGF-I/IGFBP-3 molar ratios (0.177998 +/- 0.039404) than men of same age group (0.228326 +/- 0.050979, p < 0.01) and women < or = 50 years (0.247667 +/- 0.069411, p < 0.01). Age was shown to positively correlate with GH/IGF-I (r = 0.49, p < 0.05) and GH/IGFBP-3 ratios (r = 0.40, p < 0.05) in women.

CONCLUSIONS

The influence of aging on serum concentrations of IGF-I is more remarkable in women than in men. Menopause causes reduction of IGF-I/IGFBP-3 molar ratio. Women have the trend of progressive hypoactivity of GH to stimulate IGF-I and IGFBP-3 secretions with age.

Bone mineral density in young adult survivors of acute lymphoblastic leukemia

BACKGROUND

The purpose of the current study was to determine the prevalence of low bone mineral density (BMD) (ie, osteopenia) and identify factors associated with low BMD in young adult survivors of childhood acute lymphoblastic leukemia (ALL).

METHODS

Dual energy x-ray absorptiometry was used to evaluate BMD in 74 randomly selected, long-term childhood ALL survivors initially treated in Minneapolis/St. Paul, Minnesota. Growth hormone (GH)-releasing hormone-arginine stimulation testing was conducted to evaluate peak GH level, and insulin-like growth factor I (IGF-I) and other markers of endocrine functioning were also evaluated in relation to BMD.

RESULTS

The mean age at the time of interview was 30 years, and the mean time since diagnosis was 24 years. Low BMD (Z-score, < or = -1) was present in 24% of subjects, including 1 with osteoporosis. Low BMD was substantially more prevalent in men than in women and was strongly associated with short height. The mean height Z-score for those with low BMD was -1.44, compared with a height Z-score of -0.39 (P < .01) for those with normal BMD. GH insufficiency, low IGF-I Z-score, and current smoking were also suggestive risk factors for low BMD.

CONCLUSIONS

In this long-term follow-up study of childhood ALL survivors, low BMD was found to be more prevalent than expected based on population normative data, specifically in men. The health consequences of early-onset BMD problems in childhood ALL survivors need to be carefully monitored.