Harmonization of growth hormone measurements with different immunoassays by data adjustment

Personalized medicine in acromegaly: The ACROFAST study

Medical treatment of acromegaly is currently performed through a trial-error approach using first generation somatostatin receptor ligands (fgSRLs) as first-line drugs, with an effectiveness of about 50%, and subsequent drugs are indicated through clinical judgment. Some biomarkers can predict fgSRLs response. Here we report the results of the ACROFAST study, a clinical trial in which a protocol based on predictive biomarkers of fgSRLs was evaluated.

METHODS AND SUBJECTS

prospective trial (21 university hospitals) comparing the effectiveness and time-to control of two treatment protocols during 12 months: A) A personalized protocol in which first option were fgSRLs as monotherapy or in combination with pegvisomant or, pegvisomant as monotherapy depending on the short Acute Octreotide Test (sAOT) results, tumor T2 Magnetic Resonance (MRI) signal or immunostaining for E-cadherin and, B) A control group with treatment always started by fgSRLs and the other drugs included after demonstrating inadequate control.

RESULTS

Eighty-five patients participated; 45 in the personalized and 40 in the control group. More patients in the personalized protocol achieved hormonal control compared to those in the control group (78% vs 53%, p < 0.05). Survival analysis revealed a hazard ratio for achieving hormonal control adjusted by age and sex of 2.53 (CI 1.30-4.80). Patients from personalized arm were controlled in a shorter period of time (p = 0.01).

CONCLUSION

Personalized medicine is feasible using a relatively simple protocol and allows a higher number of patients achieving control in a shorter period of time.

Revisiting the usefulness of the short acute octreotide test to predict treatment outcomes in acromegaly

Introduction

We previously described that a short version of the acute octreotide test (sAOT) can predict the response to first-generation somatostatin receptor ligands (SRLs) in patients with acromegaly. We have prospectively reassessed the sAOT in patients from the ACROFAST study using current ultra-sensitive GH assays. We also studied the correlation of sAOT with tumor expression of E-cadherin and somatostatin receptor 2 (SSTR2) .

Methods

A total of 47 patients treated with SRLs for 6 months were evaluated with the sAOT at diagnosis and correlated with SRLs' response. Those patients whose IGF1 decreased to <3SDS from normal value were considered responders and those whose IGF1 was ≥3SDS, were considered non-responders. The 2 hours GH value (GH2h) after s.c. administration of 100 mcg of octreotide was used to define predictive cutoffs. E-cadherin and SSTR2 immunostaining in somatotropinoma tissue were investigated in 24/47 and 18/47 patients, respectively.

Results

In all, 30 patients were responders and 17 were non-responders. GH2h was 0.68 (0.25-1.98) ng/mL in responders vs 2.35 (1.59-9.37) ng/mL in non-responders (p<0.001). GH2h = 1.4ng/mL showed the highest ability to identify responders (accuracy of 81%, sensitivity of 73.3%, and specificity of 94.1%). GH2h = 4.3ng/mL was the best cutoff for non-response prediction (accuracy of 74%, sensitivity of 35.3%, and specificity of 96.7%). Patients with E-cadherin-positive tumors showed a lower GH2h than those with E-cadherin-negative tumors [0.9 (0.3-2.1) vs 3.3 (1.5-12.1) ng/mL; p<0.01], and patients with positive E-cadherin presented a higher score of SSTR2 (7.5 ± 4.2 vs 3.3 ± 2.1; p=0.01).

Conclusion

The sAOT is a good predictor tool for assessing response to SRLs and correlates with tumor E-cadherin and SSTR2 expression. Thus, it can be useful in clinical practice for therapeutic decision-making in patients with acromegaly.

Arginine-stimulated copeptin in children and adolescents

OBJECTIVE

Copeptin is secreted in isomolar amounts along with arginine vasopressin peptide (AVP) from the neurohypophysis. Its stability makes it a perfect candidate for the endocrine approach in the diagnosis of AVP deficiency (AVPD; cranial diabetes insipidus; CDI). However, pediatric reference values are lacking.

DESIGN AND PATIENTS

This is a monocentric retrospective analysis of donated residual serum samples from 72 children and adolescents who underwent arginine or growth hormone-releasing hormone-arginine stimulation to test GH secretory capacity from 2018 to 2022.

MEASUREMENTS

Copeptin was measured in baseline, 30-, and 60-min samples by BRAHMS Copeptin proAVP Kryptor immunofluorescence assay.

RESULTS

Of the 72 patients, 4 suffered from complete AVPD (CDI). The baseline level of copeptin in the 68 non-AVPD (non-CDI) patients was highly variable (range: 1.3-44.4 pmol/L). The increase after arginine was moderate (30 min range: 1.6-40.4 pmol/L). The median baseline and peak copeptin levels were 5.6 and 8.0 pmol/L, respectively. The 2.5th percentile of the baseline and peak values of copeptin were 2.1 and 3.3 pmol/L, respectively. The increase and peak value of copeptin were inversely related to age (R = -.405; p = .011, and R = -.335; p = .0072, respectively) but not to gender, body mass index (standard deviation score) or GH secretion. In the four patients with AVPD (CDI), baseline or stimulated copeptin was below the 2.5th percentile of non-AVPD (non-CDI) patients.

CONCLUSIONS

Stimulated copeptin is a promising parameter for the differential diagnosis of polyuria-polydipsia syndrome. However, the low copeptin increase after arginine and the high limit of quantification of the assay are problematic for use in paediatrics.

Adult height after treatment of neurosecretory dysfunction and comparison to idiopathic GHD

OBJECTIVE

Neurosecretory dysfunction (NSD) causes growth hormone deficiency (GHD). Data on adult height after recombinant human growth hormone (rhGH) treatment are lacking.

DESIGN AND PATIENTS

We collected treatment data of all patients with NSD seen between 1990 and 2017 at our outpatient department (tertiary centre) and measured adult height. For comparison, patients with idiopathic GHD were used. Diagnoses were based on short stature (<-2 standard deviation score [SDS]), continuously low height velocity (<25th percentile), delayed bone age (by >1 SD) and low serum IGF-1 concentration (<-2 SDS). NSD was defined by normal GH challenge results, but subnormal spontaneous GH secretion. Exclusion criteria were no information on adult height, underweight and other short stature disorders.

RESULTS

Out of 67 patients diagnosed with NSD, six were still growing, 31 had test results exceeding validated GH cut-offs and three had other disorders causing short stature. Out of the 25 eligible patients with NSD, 21 could be recruited. These patients reached an adult height of -0.85 SDS (mean); 0.34 SDS below midparental height. Height gain during treatment was 2.01 SDS. This outcome was not different to 32 patients with idiopathic GHD.

CONCLUSIONS

Long-term results suggest the viability of the diagnosis of NSD and the efficacy of rhGH treatment.

Comparative study of human growth hormone measurements: impact on clinical interpretation

OBJECTIVES

Human growth hormone (hGH) provocation test is an essential tool to assess growth hormone deficiency (GHD) in children and young adults. It is important to have a robust method to determine the hGH peak of stimulation. This work aimed to compare three common automated immunoassays for hGH quantification and to ascertain whether there are still result-related differences which can impact clinical decision.

METHODS

We analyzed the GH provocation test for 39 young subjects from pediatric department of Montpellier hospital, admitted for suspicion of growth hormone deficiency. The full range of measurements as well as the peak level of serum GH were compared using three automated immunoassays on three different immunoanalyzers: IDS-hGH on iSYS, LIAISON-hGH on Liaison XL and Elecsys ROCHE-hGH, on COBAS 8000.

RESULTS

A good correlation was obtained between methods for all measurements (r ²>0.99) by using Passing-Bablok regression analysis. Bland-Altman analysis showed the best agreement between IDS-hGH and LIAISON-hGH systems (bias=-14.5%) compared to Elecsys ROCHE-hGH (bias=28.3%). When considering stratification of the study population and a unique cutoff, there were some discrepancies in interpretation of the results especially concerning the more recent Elecsys ROCHE-hGH assay. Nevertheless, when the adequate cutoff for each method was taken into account results were well correlated for all systems.

CONCLUSIONS

A cutoff for Elecsys Roche-hGH method was established to better explain the results. Clinician must be aware of the use of assay-specific cutoff to correctly integrate the results of GH tests in the GHD diagnosis.

ANA positivity and complement level in pleural fluid are potential diagnostic markers in discriminating lupus pleuritis from pleural effusion of other aetiologies

OBJECTIVE

Lupus pleuritis is the most common pulmonary manifestation of systemic lupus erythematosus (SLE). We aimed to compare various biomarkers in discriminating between pleural effusions due to lupus pleuritis and other aetiologies.

METHODS

We determined in 59 patients (16 patients with SLE and 43 patients without SLE) pleural fluid levels of high-mobility group box 1, soluble receptor for advanced glycation end products (sRAGE), adenosine deaminase (ADA), interleukin (IL) 17A, tumour necrosis factor-α, antinuclear antibodies (ANA), and complements C3 and C4.

RESULTS

We found significant differences in the pleural fluid level of sRAGE, ADA, IL-17A, C3 and C4, and in the proportion of ANA positivity, among lupus pleuritis and other groups with pleural effusion. Specifically, ANA positivity (titre ≥1: 80) achieved a high sensitivity of 91%, specificity of 83% and negative predictive value (NPV) of 97% in discriminating lupus pleuritis from non-lupus pleural effusion. A parallel combination of the level of C3 (<24 mg/dL) and C4 (<3 mg/dL) achieved a sensitivity of 82%, specificity of 89% and NPV of 93% in discriminating lupus pleuritis from non-lupus exudative pleural effusion.

CONCLUSIONS

In conclusion, ANA, C3 and C4 in pleural fluid are useful in discriminating lupus pleuritis from pleural effusion due to other aetiologies with high NPV.

Comparisons of plasma aldosterone and renin data between an automated chemiluminescent immunoanalyzer and conventional radioimmunoassays in the screening and diagnosis of primary aldosteronism

Determining values of plasma renin activity (PRA) or plasma active renin concentration (ARC), plasma aldosterone concentration (PAC), and aldosterone-to-renin ratio (ARR) is essential to diagnose primary aldosteronism (PA), but it takes several days with conventional radioimmunoassays (RIAs). Chemiluminescent enzyme immunoassays for PAC and ARC using the Accuraseed^® immunoanalyzer facilitated the determination, but relations between Accuraseed^® immunoanalyzer-based and RIA-based values in samples of PA confirmatory tests and adrenal venous sampling remained to be elucidated. We addressed this issue in the present study. This is a prospective, cross-sectional study. ARC and PAC values were measured by the Accuraseed^® immunoanalyzer in samples, in which PRA and PAC values had been measured by the PRA-FR^® RIA and SPAC^®-S Aldosterone kits, respectively. The relations between Accuraseed^® immunoanalyzer-based and RIA-based values were investigated with regression analyses. The optimal cutoff of Accuraseed^® immunoanalyzer-based ARR for PA screening was determined by the receiver operating characteristic analysis. After log-log transformations, linear relations with high coefficients of determination were observed between Accuraseed^® immunoanalyzer-based and RIA-based data of renin and aldosterone. Following the PA guidelines of Japan Endocrine Society, Accuraseed^® immunoanalyzer-based cutoffs were calculated from the regression equations: the basal PAC for PA screening >12 ng/dL, PAC for the saline infusion test >8.2 ng/dL, ARC for the furosemide-upright test <15 pg/mL, and ARR for the captopril challenge test >3.09 ng/dL per pg/mL. The optimal cutoff of Accuraseed^® immunoanalyzer-based ARR for PA screening was >2.43 ng/dL over pg/mL not to overlook bilateral PA patients. The present study provided conversion formulas between Accuraseed^® immunoanalyzer-based and RIA-based values of renin, aldosterone, and ARR, not only in basal samples but also in samples of PA confirmatory tests and adrenal venous sampling. Although validation studies are awaited, the present study will become priming water of harmonization of renin and aldosterone immunoassays.

Provocative growth hormone testing in children: how did we get here and where do we go now?

OBJECTIVES

Provocative growth hormone (GH) tests are widely used for diagnosing pediatric GH deficiency (GHD). A thorough understanding of the evidence behind commonly used interpretations and the limitations of these tests is important for improving clinical practice.

CONTENT

To place current practice into a historical context, the supporting evidence behind the use of provocative GH tests is presented. By reviewing GH measurement techniques and examining the early data supporting the most common tests and later studies that compared provocative agents to establish reference ranges, the low sensitivity and specificity of these tests become readily apparent. Studies that assess the effects of patient factors, such as obesity and sex steroids, on GH testing further bring the appropriateness of commonly used cutoffs for diagnosing GHD into question.

SUMMARY AND OUTLOOK

Despite the widely recognized poor performance of provocative GH tests in distinguishing GH sufficiency from deficiency, limited progress has been made in improving them. New diagnostic modalities are needed, but until they become available, clinicians can improve the clinical application of provocative GH tests by taking into account the multiple factors that influence their results.

GH deficiency in cancer survivors in the transition age: diagnosis and therapy

BACKGROUND

Survival rates among childhood cancer survivors (CCSs) have significantly risen in the last 40 years due to substantial improvements in treatment protocols. However, this improvement has brought with it serious late effects that frequently involve the endocrine system. Of the endocrine disorders, GH deficiency (GHD) is the most common among CCSs as a consequence of a history of cancers, surgery, and/or radiotherapy involving the hypothalamo-pituitary region.

METHODS

A comprehensive search of English language articles regardless of age was conducted in the MEDLINE database between December 2018 and October 2019. We selected all studies on GH therapy in CCSs during the transition age regarding the most challenging topics: when to retest; which diagnostic tests and cut-offs to use; when to start GH replacement therapy (GHRT); what GH dose to use; safety; quality of life, compliance and adherence to GHRT; interactions between GH and other hormonal replacement treatments.

RESULTS

In the present review, we provide an overview of the current clinical management of challenges in GHD in cancer survivors in the transition age.

CONCLUSIONS

Endocrine dysfunction among CCSs has a high prevalence in the transition age and increase with time. Many endocrine disorders, including GHD, are often not diagnosed or under-diagnosed, probably due to the lack of specialized centers for the long-term follow-up. Therefore, it is crucial that transition specialized clinics should be increased in terms of number and specific skills in order to manage endocrine disorders in adolescence, a delicate and complex period of life. A multidisciplinary approach, also including psychological counseling, is essential in the follow-up and management of these patients in order to minimize their disabilities and maximize their quality of life.

Diagnosis and Treatment of Growth Hormone Deficiency: A Position Statement from Korean Endocrine Society and Korean Society of Pediatric Endocrinology

Growth hormone (GH) deficiency is caused by congenital or acquired causes and occurs in childhood or adulthood. GH replacement therapy brings benefits to body composition, exercise capacity, skeletal health, cardiovascular outcomes, and quality of life. Before initiating GH replacement, GH deficiency should be confirmed through proper stimulation tests, and in cases with proven genetic causes or structural lesions, repeated GH stimulation testing is not necessary. The dosing regimen of GH replacement therapy should be individualized, with the goal of minimizing side effects and maximizing clinical improvements. The Korean Endocrine Society and the Korean Society of Pediatric Endocrinology have developed a position statement on the diagnosis and treatment of GH deficiency. This position statement is based on a systematic review of evidence and expert opinions.

Impact of the Choice of IGF-I Assay and Normative Dataset on the Diagnosis and Treatment of Growth Hormone Deficiency in Children

BACKGROUND

The analysis of insulin-like growth factor I (IGF-I) is an important tool for pediatricians in the diagnosis and treatment of growth hormone deficiency in children. However, significant differences exist in IGF-I assays and normative datasets, which can have important clinical consequences.

METHODS

IGF-I analyses were performed using the IDS-iSYS platform on 1,897 samples from pediatric patients (0.5-18 years old). Z-scores were calculated based on normative IGF-I data from Bidlingmaier et al. (SD-BM) [J Clin Endocrinol Metab. 2014 May; 99(5): 1712-21] and normative IGF-I data from the IGF-I harmonization program in the Netherlands (SD-NL). The differences in Z-scores were analyzed at relevant clinical decision points (-2 SD, +2 SD). These normative datasets were also compared to normative data reported by Elmlinger et al. [Clin Chem Lab Med. 2004; 42(6): 654-64].

RESULTS

The difference in Z-score between SD-BM and SD-NL was highest in males between 0 and 3 years old, exceeding 2 SD. Clinically relevant discordance between both Z-scores at -2 and +2 SD was found in 12.7% of all samples. The IGF-I levels at -2 and +2 SD reported in the normative dataset of Elmlinger et al. were up to 100% higher than the IGF-I levels reported by Bidlingmaier et al. or the Dutch harmonization program.

CONCLUSION

Pediatricians and laboratory specialists should be aware of relevant differences that can exist between IGF-I assays and normative data. Well-defined pediatric reference ranges for the IDS-iSYS platform are highly desirable.

Effects of Growth Hormone Treatment on Lipid Profiles

OBJECTIVES

To assess the effects of growth hormone (GH) on lipid profiles in children and whether the effect is pharmacological.

METHODS

The authors determined serum levels of total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), non-high-density lipoprotein cholesterol (non-HDL-C), and low-density lipoprotein cholesterol (LDL-C) every year during 3-y GH treatment in 48 GH deficient (GHD) short children and 22 children with short stature born small for gestational age (SGA).

RESULTS

The abnormally high levels of TC, non-HDL-C, and LDL-C showed a high frequency in GHD short children compared with epidemiological studies in Japan. The high prevalence of high level of TC was also shown in SGA short children. Three-year GH treatment decreased serum TC, non-HDL-C, and LDL-C levels in both patient groups.

CONCLUSIONS

GH treatment is clearly a pharmacological therapy in SGA short children and so may also be in GHD short children at the Japanese standard therapeutic dose. Taken together, GH improves lipid profiles, and its effect has the possibility of medical properties.

Gender has to be taken into account in diagnosing adult growth hormone deficiency by the GHRH plus arginine test

OBJECTIVE

Data on the effect of gender on the interpretation of the GHRH plus arginine stimulation test (GHRH+ARG test) is controversial. We validated the GHRH+ARG stimulation test in control subjects and patients with organic or idiopathic pituitary disease and a suspicion of adult growth hormone deficiency (AGHD) using the Immulite 2000 XPi GH assay.

DESIGN

We studied 126 apparently healthy adults (median age 38.8years) and 34 patients with a suspicion of AGHD (median age 42.2years). Identification of AGHD with the GHRH+ARG test was investigated with commonly accepted BMI-related consensus cut-off limits for peak GH concentrations. Serum samples collected during the GHRH+ARG test were analysed for GH in 2014-2015. Serum IGF-1 concentrations were studied as a reference.

RESULTS

In 14 of 65 (22%) control males the GH peak value was below the BMI-related cut-off limits for GH sufficiency indicating a false diagnosis of AGHD. All control females had a normal GHRH+ARG response. Median peak GH response was significantly (p<0.001) higher in female (39.3μg/L) than in male controls (21μg/L). According to consensus cut-offs all but one young female patient had a deficient response compatible with a diagnosis of AGHD.

CONCLUSIONS

The GH response to stimulation by GHRH+ARG is gender-dependent, being lower in healthy males than in females. Gender should be considered when defining cut-off limits for peak GH concentrations in the GHRH+ARG test. The presently used BMI-related cut-off levels will lead to a significant misclassification of males as GH deficient.

Anthropometric factors have significant influence on the outcome of the GHRH-arginine test: establishment of normative data for an automated immunoassay specifically measuring 22 kDa human growth hormone

CONTEXT

Adult growth hormone (GH) deficiency (GHD) is diagnosed by provocative testing of GH secretion.

OBJECTIVE

To improve the diagnostic accuracy of GH-releasing hormone (GHRH) plus arginine (GARG) testing, we evaluated the influence of age, BMI and sex and established normative data for an automatic immunoassay specifically measuring 22 kDa human GH.

DESIGN/SETTING

Prospective multicenter study.

PARTICIPANTS

Eighty-seven patients with hypothalamic-pituitary disease and 200 healthy controls. Patients were classified according to the number of pituitary hormone deficiencies (PHD). GHD was assumed when ≥2 PHD (in addition to GH) were present (n = 51); 36 patients with <2 PHD were considered GH sufficient (GHS). ROC analysis identified cutoffs with ≥95% specificity for GHD. Controls were prospectively stratified for sex, age and BMI.

INTERVENTIONS

All participants received GHRH and l-arginine.

MAIN OUTCOME MEASURES

GH was measured by immunoassay (iSYS, IDS).

RESULTS

In controls, multiple stepwise regression analysis showed that BMI (21%, P < 0.0001), sex (20%, P < 0.0001) and age (5%, P < 0.001), accounted for 46% of GH peak level variability during GARG. Comparison of peak GH during GARG (GHD vs GHS + controls) revealed an overall cutoff of 3.9 ng/mL (sensitivity 86%, specificity 95%). After adjustment for BMI and sex, optimal cutoffs (male vs female) were 6.5 vs 9.7 ng/mL in lean, 3.5 vs 8.5 ng/mL in overweight and 2.2 vs 4.4 ng/mL in obese subjects respectively.

CONCLUSION

BMI and sex account for most of the variability of peak GH levels during GARG. Consequently, diagnostic accuracy of the GARG test is significantly improved by use of adjusted cutoffs.

Diagnosis of growth hormone deficiency in the paediatric and transitional age

Growth hormone deficiency is a rare cause of childhood short stature, but one for which treatment exists in the form of recombinant human growth hormone. A diagnosis of growth hormone deficiency is made based on auxology, biochemistry and imaging. Although no diagnostic gold standard exists, growth hormone provocation tests are considered the mainstay of diagnostic investigations. However, these must be interpreted with caution in view of issues with variability and reproducibility, as well as the limited evidence-base for cut-off values used to distinguish growth hormone deficient and non-growth hormone deficient subjects. In addition, nutritional and pubertal status can affect results, with no consensus on the role of priming with sex steroid hormones. Difficulties with assays exist both for growth hormone as well as insulin-like growth factor-1. Pituitary magnetic resonance imaging is a useful diagnostic, and possibly prognostic, aid. Although genetic testing is not routine, the discovery of more relevant mutations makes it an increasingly important investigation. Children with growth hormone deficiency are retested biochemically on completion of growth, to assess whether they remain so into adulthood.

Interpreting biochemical control response rates with first-generation somatostatin analogues in acromegaly

CONTEXT

The somatostatin analogues octreotide LAR and lanreotide Autogel have been evaluated for the treatment of acromegaly in numerous clinical trials, with considerable heterogeneity in reported biochemical response rates. This review examines and attempts to account for these differences in response rates reported in the literature.

EVIDENCE ACQUISITION

PubMed was searched for English-language studies of a minimum duration of 24 weeks that evaluated ≥10 patients with acromegaly treated with octreotide LAR or lanreotide Autogel from 1990 to March 2015 and reported GH and/or IGF-1 data as the primary objective of the study.

EVIDENCE SYNTHESIS

Of the 190 clinical trials found, 18 octreotide LAR and 15 lanreotide Autogel studies fulfilled the criteria for analysis. It is evident from the protocols of these studies that multiple factors are capable of impacting on reported response rates. Prospective studies reporting an intention-to-treat analysis that evaluated medically naïve patients and used the composite endpoint of both GH and IGF-1 control were associated with lower response rates. The use of non-composite biochemical control endpoints, heterogeneous patient populations, analyses that exclude treatment non-responders, assay variability and prior responsiveness to medical therapy are just a few of the factors identified that likely contribute to higher success rates.

CONCLUSIONS

The wide range of reported response rates with somatostatin analogues may be confusing and could lead to misinterpretation by both the patient and the physician in certain situations. Understanding the factors that potentially drive the variation in response rates should allow clinicians to better gauge treatment expectations in specific patients.

Evaluation of growth hormone stimulation testing in children

OBJECTIVE

To evaluate the use and interpretation of growth hormone (GH) stimulation tests used across the UK for diagnosing GH deficiency.

BACKGROUND

Previous studies show poor consensus on the use of GH stimulation tests. Sex steroid priming and retesting in the transition period are areas not previously surveyed.

DESIGN

Data were collected from tertiary paediatric endocrinologists, paediatricians with a specialist interest in endocrinology and biochemists across the UK over 6 months through distributing electronic surveys.

RESULTS

At least three different GH stimulation tests were used by 33% of departments. Glucagon and insulin doses varied most, and sampling frequency varied most using insulin. All laboratories use a recommended chemiluminescence immunoassay with an acceptable coefficient of variability. The GH peak for diagnosing GH deficiency varied from 6 to 8 μg/l. A wide range of clinical scenarios prompted retesting in the transition period, suggesting nonstandardized current practice. Seventy-five per cent of departments use sex steroid priming, but follow criteria variously combining bone age, chronological age and pubertal stage, together with variations in steroid type and dose.

CONCLUSIONS

Although a contentious diagnostic test, GH stimulation tests remain the gold standard for diagnosing GH deficiency. Our data suggest that together with variation in indication, protocol and interpretation, there is considerable variation in current practices pertaining to priming and retesting in transition. Given the current financial climate and the need for careful resource management, this study emphasizes the considerable need for consensus in the investigation, diagnosis and long-term follow-up of these children, at least nationally if not internationally.

Evaluation of the GHRH-arginine retest for young adolescents with childhood-onset GH deficiency

OBJECTIVE

Retesting of adolescents with childhood-onset GH deficiency (GHD) is recommended, but age-related reference data are scarce. We aimed to establish a cut-off value for the GHRH-arginine test (GHRH+ARG) at the typical age of retesting at near-adult height.

DESIGNS

We retrospectively studied 149 patients (108 males) with childhood-onset GHD aged 16.8 ± 1.7 years (mean ± SD) with a BMI of 20.9 ± 3.5 kg/m(2) who had received GHRH+ARG in one single center during 8 consecutive years. Based on the IGF-I serum concentration falling below -2 SDS when off GH, 22 patients suffered from severe GHD of adulthood while 122 were GH sufficient. Five patients could not be determined definitively. GH and IGF-I were measured by in-house RIAs. IGF-I values were transformed into age-related SDS values. ROC-analysis was used to determine the cut-off value.

RESULTS

For GHRH+ARG, a cut-off limit of 15.9 ng/ml had the highest pair of sensitivity (91%) and specificity (88%). GH peaks of the patients with a normal BMI between -1 and 0 SDS were higher than those with a high BMI >1 SDS (p<0.01).

CONCLUSIONS

When retesting adolescents at near-adult height for severe GHD of adulthood, a GH value of <15.9 ng/ml in GHRH+ARG is discriminatory with good accuracy. Conversion factors for other GH assays in use are provided. A rational decision for or against the continuation of GH therapy into adulthood can be made based on the clinical history of the patient and the combination of the GHRH+ARG retest result and the IGF-I serum concentrations when off GH.

Modified Clonidine Testing for Growth Hormone Stimulation Reveals α2-Adrenoreceptor Sub Sensitivity in Children with Idiopathic Growth Hormone Deficiency

Introduction

The association between short stature and increased risk of ischemic heart disease has been subject to studies for decades. The recent discussion of cardiovascular risk during growth hormone therapy has given new importance to this question. We have hypothesized that the autonomic system is a crucial element relating to this subject.

Methods

Heart rate variability calculated from 24-hour electrocardiogram data is providing insight into the regulatory state of the autonomous nervous system and is an approved surrogate parameter for estimating cardiovascular risk. We have calculated heart rate variability during clonidine testing for growth hormone stimulation of 56 children. As clonidine is a well-known effector of the autonomous system, stimulating vagal tone and decreasing sympathetic activity, we compared the autonomous reactions of children with constitutional growth delay (CGD), growth hormone deficiency (GHD) and former small for gestational age (SGA).

Results

During clonidine testing children with CGD showed the expected α₂-adrenoreceptor mediated autonomous response of vagal stimulation for several hours. This vagal reaction was significantly reduced in the SGA group and nearly non- existent in the GHD group.

Discussion

Children with GHD show a reduced autonomous response to clonidine indicating α₂-adrenoreceptor sub sensitivity. This can be found prior to the start of growth hormone treatment. Since reduction of HRV is an approved surrogate parameter, increased cardiovascular risk has to be assumed for patients with GHD. In the SGA group a similar but less severe reduction of the autonomous response to clonidine was found. These findings may enrich the interpretation of the data on growth hormone therapy, which are being collected by the SAGhE study group.

Hormone replacement therapy in children: The use of growth hormone and IGF-I

Recombinant human GH (rhGH) has been available since 1985. This article gives an overview, what has been achieved over the past 30 years in respect to optimization of rhGH treatment for the individual child with GH deficiency and what are the safety issues concerned with this treatment. In the last twenty years significant scientific progress has been made in the diagnosis of GH deficiency, the genetic disorders that are associated with pituitary GH deficiency and the genetics that influence growth in general. On the other hand rhGH is not only used in states of GH deficiency but also various conditions without a proven GH deficiency by classical standards. Clinical studies that investigated both the genetics of growth and the individual responses to rhGH therapy in these patient populations were able to refine our concept about the physiology of normal growth. In most patients under rhGH treatment there is a considerable short-term effect, however the overall gain in growth obtained by a long-term treatment until final height still remains a matter of debate in some of the conditions treated. Also first studies on the long-term safety risks of rhGH treatment have raised the question whether this treatment is similarly safe for all the patient groups eligible for such a treatment. Therefore even in the face of a longstanding safety record of this drug replacement therapy the discussion about the right cost and risk to benefit ratio is continuing. Consequently there is still a need for carefully conducted long-term studies that use modern anthropometric, genetic, and laboratory techniques in order to provide the necessary information for clinicians to select the patients that will benefit best from this valuable treatment without any long term risk.

Clinical evidence-based cutoff limits for GH stimulation tests in children with a backup of results with reference to mass spectrometry

CONTEXT

Cutoff limits of GH stimulation tests to diagnose GH deficiency (GHD) in children and adolescents are not sufficiently validated by clinical studies due to discrepancies in the performance of GH immunoassays and lack of available study populations.

OBJECTIVE

We aimed to establish new cutoff limits for GH stimulation tests based on clinical evidence and compared these immunoassay-based values with an antibody-independent mass spectrometric method.

DESIGN AND SETTING

In a retrospective study, GH cutoff limits for eight different immunoassays and isotope dilution mass spectrometry (ID-MS) were calculated from hGH peak concentrations of short-statured children with and without GHD.

PATIENTS

We compared the serum GH peak concentrations at GH stimulation test of 52 short-statured children and adolescents, who have normal GH secretion at initial workup and normal growth in the follow-up, with the serum GH peak concentrations of 44 GHD patients in the same age range, in order to optimize the cutoff limit calculation.

RESULTS

Discriminant analysis of re-measured GH led to a new cutoff limit of 7.09 μg/l using the iSYS assay (IDS) and the limits for the other seven hGH assays varied between 4.32 and 7.77 μg/l. For ID-MS, cutoffs of 5.48 μg/l (22k GH) and 7.43 μg/l (total GH) were ascertained.

CONCLUSION

The establishment of method-specific clinical evidence-based GH cutoff limits is of importance to ensure adequate clinical diagnosis and treatment of children and adolescents with GHD. ID-MS may become an important tool for providing both reliable and sustainable SI traceability of GH measurements in the future.

Isolated growth hormone deficiency (GHD) in childhood and adolescence: recent advances

The diagnosis of GH deficiency (GHD) in childhood is a multistep process involving clinical history, examination with detailed auxology, biochemical testing, and pituitary imaging, with an increasing contribution from genetics in patients with congenital GHD. Our increasing understanding of the factors involved in the development of somatotropes and the dynamic function of the somatotrope network may explain, at least in part, the development and progression of childhood GHD in different age groups. With respect to the genetic etiology of isolated GHD (IGHD), mutations in known genes such as those encoding GH (GH1), GHRH receptor (GHRHR), or transcription factors involved in pituitary development, are identified in a relatively small percentage of patients suggesting the involvement of other, yet unidentified, factors. Genome-wide association studies point toward an increasing number of genes involved in the control of growth, but their role in the etiology of IGHD remains unknown. Despite the many years of research in the area of GHD, there are still controversies on the etiology, diagnosis, and management of IGHD in children. Recent data suggest that childhood IGHD may have a wider impact on the health and neurodevelopment of children, but it is yet unknown to what extent treatment with recombinant human GH can reverse this effect. Finally, the safety of recombinant human GH is currently the subject of much debate and research, and it is clear that long-term controlled studies are needed to clarify the consequences of childhood IGHD and the long-term safety of its treatment.

The harmonisation of growth hormone measurements: taking the next steps

For over 20 years differences in results of growth hormone (GH) measurement have been recognised as being significant enough to lead to misdiagnosis and inappropriate management of patients with GH-related disorders. Whilst issues of method standardisation, variable antibody specificity, use of different reporting units with different conversion factors, and interference from GH binding protein have been acknowledged as contributing to the discrepancies, inconsistent approaches to method harmonisation have hampered opportunities to enhance the evidence base for GH measurements. Amongst the first steps to be taken, international collaboratives recommended the universal adoption of the International Standard 98/547 and the reporting of results in mass units. Whilst inter-method variability may have improved over the last 10 years, clinically significant differences remain. A more recently recognised issue contributing to the discrepancies may be the differences in the matrix materials used by kit manufacturers to assign values to their calibrants. The establishment of an international harmonisation oversight group is recommended: its key roles to include identification of a commutable matrix reference material, assessing the clinical significance of assay interferents, the evaluation of liquid chromatography-mass spectrometry as a reference measurement procedure and the provision of acceptance criteria for the clinical application of GH methods.

Growth hormone values after an oral glucose load do not add clinically useful information in patients with acromegaly on long-term somatostatin receptor ligand treatment

The optimal method of assessing GH status in acromegalic patients receiving medical therapy with somatostatin analogs (SSA) has been matter of debate. The aim of the study has been to investigate whether OGTT may add information in patients with discordant random GH (GHr) and IGF values. Moreover, we evaluated the association of GH nadir with the prevalence of co-morbidities observed in acromegalic patients on SSA therapy. We evaluated 130 patients with proven diagnosis of acromegaly on SSA. The patients were subdivided in three groups: patients with controlled disease (both safe random GH and normal IGF-I, group A, 20.0 %), patients with uncontrolled disease (both high random GH and IGF-I, group B, 34.6 %), and patients with discordant random GH and IGF-I values (group C, 35.4 %). A high concordance rate for GH nadir with random GH and IGF-I was observed in group B, while a significant reduced concordance rate has been observed in group A (100 % sensitivity, 64.5 % specificity). By contrast, in group C, we observed concordant results between GH nadir and IGF-I only in 14/59 patients. In group A, the prevalence of diabetes was lower than in group B or C. Safe random GH was the only single criteria associated with a lower prevalence of diabetes. Discrepant IGF-I and either GH nadir or random GH values are frequently observed in acromegalic patients treated with SSA. Concordant IGF-I and random GH may influence the prevalence of metabolic complications. GH nadir measurement may help to interpret discrepancies between random GH and IGF-I data only in few cases.

Reevaluation of Acromegalic Patients in Long-Term Remission according to Newly Proposed Consensus Criteria for Control of Disease

Acromegaly guidelines updated in 2010 revisited criteria of disease control: if applied, it is likely that a percentage of patients previously considered as cured might present postglucose GH nadir levels not adequately suppressed, with potential implications on management. This study explored GH secretion, as well as hormonal, clinical, neuroradiological, metabolic, and comorbid profile in a cohort of 40 acromegalic patients considered cured on the basis of the previous guidelines after a mean follow-up period of 17.2 years from remission, in order to assess the impact of the current criteria. At the last follow-up visit, in the presence of normal IGF-I concentrations, postglucose GH nadir was over 0.4 μg/L in 11 patients (Group A) and below 0.4 μg/L in 29 patients (Group B); moreover, Group A showed higher basal GH levels than Group B, whereas a significant decline of both GH and postglucose GH nadir levels during the follow-up was observed in Group B only. No differences in other evaluated parameters were found. These results seem to suggest that acromegalic patients considered cured on the basis of previous guidelines do not need a more intensive monitoring than patients who met the current criteria of disease control, supporting instead that the cut-off of 0.4 mcg/L might be too low for the currently used GH assay.

Gaps in the Traceability Chain of Human Growth Hormone Measurements

BACKGROUND

Human growth hormone (hGH) is measured for the diagnosis of secretion disorders. These measurements fall under the EU Directive 98/79/EC on in vitro diagnostic medical devices requiring traceability of commercial calibrator values to higher-order reference materials or procedures (Off J Eur Communities 1998 Dec 7;L 331:1–37). External quality assessment schemes show large discrepancies between results from different methods, even though most methods provide results traceable to the recommended International Standard (IS 98/574). The aim of this study was to investigate possible causes for these discrepancies.

METHODS

We investigated the commutability and recovery of hGH in reconstituted IS 98/574. We tested different reconstitution protocols and used 4 different serum matrices for spiking. These IS preparations were measured together with serum samples. We quantified hGH by 5 different methods in 4 different laboratories.

RESULTS

Results from the different methods correlated well for the serum samples. Mean discrepancies between results from different methods were ≤20%. None of the IS preparations was commutable for all the method comparisons. The recovery of hGH in preparations of IS 98/574 depended on the reconstitution protocol (&gt;10-fold differences) and BACKGROUND matrix (relative differences ≤17% for different serum matrices).

CONCLUSIONS

The use of different protocols for reconstitution and spiking of hGH reference preparations affects quantification by immunoassays, potentially leading to a bias between commercial methods, despite the use of calibrators with values claimed to be traceable to the same higher-order reference material.

Biomarker monitoring in sports doping control

Biomarker monitoring can be considered a new era in the effort against doping. Opposed to the old concept in doping control of direct detection of a prohibited substance in a biological sample such as urine or blood, the new paradigm allows a personalized longitudinal monitoring of biomarkers that indicate non-physiological responses independently of the used doping technique or substance, and may cause sanctioning of illicit practices. This review presents the development of biomarker monitoring in sports doping control and focuses on the implementation of the Athlete Biological Passport as the current concept of the World Anti Doping Agency for the detection of blood doping (hematological module). The scope of the article extends to the description of novel biomarkers and future concepts of application.

Diagnosis of growth hormone deficiency in childhood

PURPOSE OF REVIEW

The diagnosis of growth hormone deficiency (GHD) in childhood is challenging, in large part because of the lack of a true gold standard and the relatively poor performance of available diagnostic testing. This review discusses the recent literature on this topic.

RECENT FINDINGS

Auxology and clinical judgment remain the foundation for the diagnosis of GHD. Provocative growth hormone testing is poorly reproducible, dependent on factors such as body composition and pubertal status, and further limited by significant variability among commercially available growth hormone assays. Measurement of insulin-like growth factor I and insulin-like growth factor-binding protein 3 is not diagnostically useful in isolation but is helpful in combination with other diagnostic measures. Neuroimaging is also useful to inform diagnosis, as pituitary abnormalities suggest a higher likelihood of GHD persisting into adulthood. Although genetic testing is not routinely performed in the diagnosis of GHD at the present time, multiple recent reports raise the possibility that it may play a more important role in diagnosing GHD in the future.

SUMMARY

Beyond physicians' integrated assessment of auxology, clinical presentation, and bone age, current tools to diagnose GHD are suboptimal. Recent literature emphasizes the need to reappraise our current practice and to consider new tools for diagnosis.

Auxology-based cut-off values for biochemical testing of GH secretion in childhood

OBJECTIVE

The diagnosis of GH deficiency (GHD) in childhood requires GH tests with arbitrary cut-offs. We aimed to define GH cut-offs based on auxology.

DESIGN

From a total of 349 children diagnosed with GHD between 1985 and 2005 at our hospital, we excluded all children who had additional characteristics likely to interfere with growth velocity. Age at start of therapy was defined as 4 to 8/9 years (girls/boys). Auxological inclusion criteria were pathological growth velocity, height at start of therapy >1.5 SD below the target, and efficient catch-up growth during GH therapy. Basal IGF-I/IGFBP-3, GH response to arginine and spontaneous GH secretion at night had been measured by the same polyclonal RIA. The reference was a group of 108 normally growing age-matched children with Turner syndrome or born small for gestational age tested during the same time period.

RESULTS

We identified 52 children with GHD who fulfilled the inclusion criteria. ROC analysis showed the best diagnostic accuracy at a peak GH cut-off for arginine of 6.6 μg/L (sensitivity, 84.3%; specificity, 75.5%; AUC=0.83) and at a peak GH cut-off during spontaneous secretion at night of 7.3 μg/L (sensitivity, 96.8%; specificity, 82.4%; AUC=0.93). Our arbitrarily defined GH cut-offs had been higher. Children diagnosed with GHD in the past with GH test values above the new cut-offs were less responsive to GH therapy (P=0.007).

CONCLUSIONS

Here we provide a new rational approach which allows the substitution of arbitrarily defined GH cut-offs by those based on auxology.