Growth hormone stimulation testing in both short and normal statured children: use of an immunofunctional assay

Idiopathic Short Stature: What to Expect from Genomic Investigations

Short stature is a common concern for physicians caring for children. In traditional investigations, about 70% of children are healthy, without producing clinical and laboratory findings that justify their growth disorder, being classified as having constitutional short stature or idiopathic short stature (ISS). In such scenarios, the genetic approach has emerged as a great potential method to understand ISS. Over the last 30 years, several genes have been identified as being responsible for isolated short stature, with almost all of them being inherited in an autosomal-dominant pattern. Most of these defects are in genes related to the growth plate, followed by genes related to the growth hormone (GH)–insulin-like growth factor 1 (IGF1) axis and RAS-MAPK pathway. These patients usually do not have a specific phenotype, which hinders the use of a candidate gene approach. Through multigene sequencing analyses, it has been possible to provide an answer for short stature in 10–30% of these cases, with great impacts on treatment and follow-up, allowing the application of the concept of precision medicine in patients with ISS. This review highlights the historic aspects and provides an update on the monogenic causes of idiopathic short stature and suggests what to expect from genomic investigations in this field.

Investigating whether serum IGF-1 and IGFBP-3 levels reflect the height outcome in prepubertal children upon rhGH therapy: LG growth study database

Serum insulin-like growth factor-1 (IGF-I) and IGF binding protein-3 (IGFBP-3) levels can be used to monitor the safety of recombinant human growth hormone (rhGH) therapy. In this study, we evaluated the changes in serum IGF-I and IGFBP-3 levels during rhGH therapy as a marker of height outcome in prepubertal children. Totally, 705 prepubertal children with short stature were enrolled from the LG Growth Study Database. Data for three groups of subjects were obtained as follows: Idiopathic GH deficiency (IGHD; n = 486); idiopathic short stature (n = 66); small for gestational age (n = 153). Serum IGF-I and IGFBP-3 levels at the baseline and after the 1^st and 2^nd year of rhGH therapy, as well as the Δheight standard deviation score (SDS), were obtained. Δheight SDS after the 1^st and 2^nd year of rhGH therapy had notably increased compared to that at the baseline for all three groups. IGF-I and IGFBP-3 levels in all three groups were significantly increased compared to those at the baseline (p <0.001). Δheight SDS was positively correlated with ΔIGF-1 SDS after the 1^st year of therapy, ΔIGFBP-3 SDS after the 2^nd year of therapy in the IGHD group, and ΔIGF-I SDS and ΔIGFBP-3 SDS after the 2^nd year of therapy (p < 0.05), regardless of whether the height at the baseline was a covariate. The increase in IGF-I and IGFBP-3 levels during rhGH therapy was related to the growth response in children with IGHD. Therefore, it may be valuable to measure the change in serum IGF-I and IGFBP-3 levels, especially the latter, during rhGH treatment to predict the growth response upon long-term treatment.

Brain MRIs may be of low value in most children diagnosed with isolated growth hormone deficiency

OBJECTIVES

Brain MRIs are considered essential in the evaluation of children diagnosed with growth hormone deficiency (GHD), but there is uncertainty about the appropriate cut-off for diagnosis of GHD and little data about the yield of significant abnormal findings in patients with peak growth hormone (GH) of 7-10 ng/mL. We aimed to assess the frequency of pathogenic MRIs and associated risk factors in relation to peak GH concentrations.

METHODS

In this retrospective multicenter study, charts of patients diagnosed with GHD who subsequently had a brain MRI were reviewed. MRIs findings were categorized as normal, incidental, of uncertain significance, or pathogenic (pituitary hypoplasia, small stalk and/or ectopic posterior pituitary and tumors). Charges for brain MRIs and sedation were collected.

RESULTS

In 499 patients, 68.1% had normal MRIs, 18.2% had incidental findings, 6.6% had uncertain findings, and 7.0% had pathogenic MRIs. Those with peak GH<3 ng/mL had the highest frequency of pathogenic MRIs (23%). Only three of 194 patients (1.5%) with peak GH 7-10 ng/mL had pathogenic MRIs, none of which altered management. Two patients (0.4%) with central hypothyroidism and peak GH<4 ng/mL had craniopharyngioma.

CONCLUSIONS

Pathogenic MRIs were uncommon in patients diagnosed with GHD except in the group with peak GH<3 ng/mL. There was a high frequency of incidental findings which often resulted in referrals to neurosurgery and repeat MRIs. Given the high cost of brain MRIs, their routine use in patients diagnosed with isolated GHD, especially patients with peak GH of 7-10 ng/mL, should be reconsidered.

Growth Hormone Stimulation Testing Patterns Contribute to Sex Differences in Pediatric Growth Hormone Treatment

INTRODUCTION

Males are twice as likely as females to receive pediatric growth hormone (GH) treatment in the USA, despite similar distributions of height z (HtZ)-scores in both sexes. Male predominance in evaluation and subspecialty referral for short stature contributes to this observation. This study investigates whether sex differences in GH stimulation testing and subsequent GH prescription further contribute to male predominance in GH treatment.

METHODS

Retrospective chart review was conducted of all individuals, aged 2-16 years, evaluated for short stature or poor growth at a single large tertiary referral center between 2012 and 2019. Multiple logistic regression models were constructed to analyze sex differences.

RESULTS

Of 10,125 children referred for evaluation, a smaller proportion were female (35%). More males (13.1%) than females (10.6%) underwent GH stimulation testing (p < 0.001) and did so at heights closer to average (median HtZ-score -2.2 [interquartile range, IQR -2.6, -1.8] vs. -2.5 [IQR -3.0, -2.0], respectively; p < 0.001). The proportion of GH prescriptions by sex was similar by stimulated peak GH level. Predictor variables in regression modeling differed by sex: commercial insurance predicted GH stimulation testing and GH prescription for males only, whereas lower HtZ-score predicted GH prescription for females only.

CONCLUSIONS

Sex differences in rates of GH stimulation testing but not subsequent GH prescription based on response to GH stimulation testing seem to contribute to male predominance in pediatric GH treatment. That HtZ-score predicted GH prescription in females but not males raises questions about the extent to which sex bias - from children, parents, and/or physicians - as opposed to objective growth data, influence medical decision-making in the evaluation and treatment of short stature.

Should We Assess Pituitary Function in Children After a Mild Traumatic Brain Injury? A Prospective Study

Objective: The aim of this study was to evaluate the frequency of hypopituitarism following TBI in a cohort of children who had been hospitalized for mild TBI and to identify the predictive factors for this deficiency. Design: A prospective study was conducted on children between 2 and 16 years of age who had been hospitalized for mild TBI according to the Glasgow Coma Scale between September 2009 and June 2013. Clinical parameters, basal pituitary hormone assessment at 0, 6, and 12 months, as well as a dynamic testing (insulin tolerance test) 12 months after TBI were performed. Results: The study included 109 children, the median age was 8.5 years. Patients were examined 6 months (n = 99) and 12 months (n = 96) after TBI. Somatotropic deficiency (defined by a GH peak <20 mUI/l in two tests, an IGF-1 <-1SDS and a delta height <0SDS) were confirmed in 2 cases. One case of gonadotrophic deficiency occurred 1 year after TBI among 13 pubertal children. No cases of precocious puberty, 5 cases of low prolactin level, no cases of corticotropic insufficiency (cortisol peak <500 nmol/l) and no cases diabetes insipidus were recorded. Conclusion: Pituitary insufficiency was present 1year after mild TBI in about 7% of children. Based on our results, we suggest testing children after mild TBI in case of clinical abnormalities. i.e., for GH axis, IGF-1, which should be assessed in children with a delta height <0 SDS, 6 to 12 months after TBI, and a dynamic GH testing (preferentially by an ITT) should be performed in case of IGF-1 <-1SDS, with a GH threshold at 20 mUI/L. However, if a systematic pituitary assessment is not required for mild TBI, physicians should monitor children 1 year after mild TBI with particular attention to growth and weight gain.

Serum α-klotho levels are not informative for the evaluation of growth hormone secretion in short children

BACKGROUND

α-Klotho is a transmembrane protein that can be cleaved and act as a circulating hormone (s-klotho). s-Klotho serum levels seem to reflect growth hormone (GH) secretory status. We investigated the role of s-klotho as a reliable marker of GH secretion in short children and the factors influencing its secretion.

METHODS

We enrolled 40 short Egyptian children (20 GH deficiency [GHD] and 20 idiopathic short stature [ISS]). They underwent a pegvisomant-primed insulin tolerance test (ITT) and were accordingly reclassified as 16 GHD and 24 ISS. The samples obtained before and 3 days after pegvisomant administration, prior to the ITT, were used for assaying insulin-like growth factor (IGF)-I and s-klotho.

RESULTS

IGF-I and s-klotho serum levels were not significantly different (p=0.059 and p=0.212, respectively) between GHD and ISS. After pegvisomant, a significant reduction in IGF-I and s-klotho levels was found in both groups. s-Klotho significantly correlated only with IGF-I levels in both groups.

CONCLUSIONS

s-Klotho mainly reflects the IGF-I status and cannot be considered a reliable biomarker for GH secretion in children.

The role of insulin like growth factor (IGF)-1 and IGF-binding protein-3 in diagnosis of Growth Hormone Deficiency in short stature children

OBJECTIVE

The purpose of this study was to evaluate the role of IGF-1 and IGFBP-3 in diagnosis of short stature children and adolescents in whom Growth Hormone Deficiency (GHD) was found.

METHODS

In this cross sectional study the referred short stature children and adolescents to Namazi Hospital in Shiraz- Iran, in 2003-2005 were studied. The inclusion criteria were proved short stature based on the physical examination, weight, height, standard deviation score (SDS) of height < -2, with considering stage of puberty and predicted height in children without any genetic or chronic disorders. The exclusion criteria were any positive physical or laboratory data suggesting hypothyroidism, rickets or liver disorders. For all patients a provocative growth hormone test was performed with propranolol and L-dopa and serum IGF-1 and IGFBP-3 were measured. GHD defined as peak(cutoff) serum GH level under 10 ìg/L and low IGF-1 and IGFBP-3 considered as cutoff serum level under -2 standard deviation.

RESULTS

Eighty one short stature patients (39 boys and 42 girls) with mean age of 10.6 +/- 3.5 years completed the study. Seventeen patients with GHD were found and in 18 patients IGF-1 level were low. Only in 6 patients both GH and IGF-1 were low and 2 of them had low IGFBP-3. There were no correlations between the levels of GH,IGF-1 and IGFBP-3 in children with short stature due to GHD. The sensitivity and specifity of IGF-1 and IGFBP-3 in assessment of GHD were 35% and 81% for IGF-1 and 12% and 94% for IGFBP-3, respectively.

CONCLUSION

No correlations were found between GH level and serum levels of IGF-1 and IGFBP-3 in short patients and the sensitivity of those tests in assessment of GHD were poor.

Influence of oral contraceptive use on growth hormone in vivo bioactivity following resistance exercise: responses of molecular mass variants

The purpose was to examine effects of oral contraceptive (OC) use on plasma growth hormone (GH) responses to heavy resistance exercise. Sixty untrained women were placed into one of two groups: currently using OC (Ortho Tri-Cyclen) (n=25; mean+/-SD: 24.5+/-4.2y, 160.4+/-7.1cm, 64.1+/-11.3kg) or not currently using OC (NOC) (n=35; 23.6+/-4.6y, 165.9+/-6.0cm, 65.7+/-10.3kg). Participants performed an acute heavy resistance exercise test (AHRET; six sets of 10 repetition squats; 2min rest between sets) during days 2-4 of the follicular phase (NOC group) or of inactive oral contraceptive intake (OC group). Plasma was obtained before and immediately after AHRET and subsequently fractionated based on apparent molecular weight (>60kD, 30-60kD, and <30kD). GH was determined in unfractionated plasma and each plasma fraction using 4 methods: (1) Nichols Institute Diagnostics immunoradiometric assay (Nichols), (2) National Institute of Diabetes and Digestive Kidney Diseases (NIDDK) competitive radioimmunoassay, (3) DSL immunofunctional enzyme-linked immunoabsorbent assay (IFA) and (4) rat tibial line bioassay. GH increased (P<0.05) in all fractions post-AHRET for the Nichols, NIDDK, and IFA. The OC group displayed higher resting GH for the NIDDK, and higher exercise-induced GH for the IFA, Nichols, and NIDDK in unfractionated plasma and >60kD subfraction compared to NOC group. No differences were observed for the tibial line bioassay. OC use augmented immunological GH response to AHRET in unfractionated plasma and >60kD molecular weight subfraction. However, OC use only increased biological activity of GH in one of two bioassays. These data demonstrated that GH concentrations at rest and following exercise are assay-dependent.

Pegvisomant-primed GH stimulation test

OBJECTIVE

Provocative stimulation tests for GH assessment have poor reproducibility and can often elicit false positive results in normal children. The aim of our study was to evaluate the capability of pegvisomant, as an enhancer of GH secretion, in unmasking false-positive results in short children undergoing GH testing.

DESIGN

A prospective study was conducted between March 2005 and April 2006.

PATIENTS

Twenty-one short children (8 males and 13 females), aged 1.0-14.5 years, with a height of < 2 SD scores below the mean were included in the study.

METHODS

All subjects underwent an L-DOPA stimulation test with evaluation of GH. At the end of the test, 1 mg/kg of pegvisomant was given subcutaneously and 3 days later an L-DOPA stimulation test was repeated.

RESULTS

There was a significant decrease of IGF-I SDS following pegvisomant (-1.75 +/- 0.24 vs.-2.65 +/- 0.23; P < 0.0001) and a significant increase of the GH-peak (6.2 +/- 0.91 vs. 15.3 +/- 2.30 microg/l; P < 0.0001). Among the 21 patients examined, 18 (85.7%) had an insufficient response (< 10 microg/l) at the first stimulation. Ten of them (55.5%) showed normal secretion after priming with pegvisomant, while insufficient secretory reserve was confirmed in the remaining eight.

CONCLUSIONS

Pegvisomant priming before GH stimulation tests can be used to improve the reliability of the diagnostic work up in GH deficiency. Further studies are required, however, to clarify whether this procedure should be recommended in the routine evaluation of GH status.

Idiopathic short stature: definition, epidemiology, and diagnostic evaluation

Idiopathic short stature is a condition in which the height of the individual is more than 2 SD below the corresponding mean height for a given age, sex and population, in whom no identifiable disorder is present. It can be subcategorized into familial and non-familial ISS, and according to pubertal delay. It should be differentiated from dysmorphic syndromes, skeletal dysplasias, short stature secondary to a small birth size (small for gestational age, SGA), and systemic and endocrine diseases. ISS is the diagnostic group that remains after excluding known conditions in short children.

Growth hormone deficiency in children

The foundation for the diagnosis of growth hormone (GH) deficiency in childhood must be auxology, that is, the comparison of the child's growth pattern to that of established norms for gender and ethnicity. It is only in those growing considerably more slowly than average that testing for GHD makes sense. Assessment of laboratory tests, whether static, for example, the measurement of growth factors or their binding proteins, or dynamic, for example, secretagogue-stimulated GH secretion is confirmatory. One must be cognizant of the assay used to determine GH, for there may be a 3-fold difference in the concentration of GH among commercially-available assays. Controversy still exists concerning the measurement of spontaneous GH release and whether sex-steroid priming is appropriate in prepubertal children. Imaging analysis may prove helpful in some children with congenital GHD or to detect a space-occupying lesion in the area of the hypothalamus and pituitary. The final diagnosis is based on multiple parameters and occasionally on a therapeutic trial of GH therapy to determine if there is a significant acceleration of growth velocity.

Growth hormone action in puberty: effects by gender

OBJECTIVE

Adult females receiving GH may be less sensitive to the metabolic effects of GH than males, however these differences are less well studied in adolescence. We aimed to investigate if metabolic effects of GH vary by gender during puberty.

DESIGN

Sixteen adolescents (8 M/8 F, mean age (SE): 13.1+/-0.2 yr) with significant short stature due to either GH insufficiency or idiopathic short stature were studied before and after 8 w of daily GH therapy. Differences in rates of protein and glycerol turnover ((13)C leucine and d5-glycerol infusions), substrate oxidation rates (indirect calorimetry), hormones, growth factors, lipid concentrations, body composition (DEXA) and 1 yr growth velocity were measured.

RESULTS

Protein synthesis rates per kg FFM were similar in boys and girls before and after GH and increased similarly on treatment in both genders. Rates of whole body lipolysis were similar at baseline and increased after GH in both genders comparably. Plasma lipids were similar between boys and girls before and after GH, and triglycerides increased post-GH in both. Insulin increased after GH comparably in both genders, yet no significant difference in glucose or adiponectin concentrations during treatment or between genders was observed. IGF-I concentrations were similar between boys and girls at baseline, but with a more robust increase in males after 8 w of GH (boys: +629+/-65 ng/ml, girls: +331+/-67, p=0.007). Body composition changes and bone mineral density were similar between genders after GH. HT SDS increased comparably after 1 yr (boys -2.2+/-0.09 to -1.77+/-0.11, p=0.0002; girls -2.49+/-0.24 to -2.02+/-0.25, p=0.04). There were no gender differences on the linear growth responses after 12 mo.

CONCLUSIONS

As compared to girls, boys had: (1) similar sensitivity to GH for protein synthesis, lipolysis, lipid concentrations and body composition changes as well as comparable glucose and adiponectin concentrations; (2) higher IGF-I responses to 8 w of GH. Differences in IGF-I during GH treatment may account in part for the gender differences in physique and strength that develop during human puberty; however, using conventional doses of GH, these differences do not translate into differences in linear growth after 12 mo. Contrary to adults, these data do not support the need for different GH dosing depending on gender during puberty.

Growth Hormone Determination in Children Using an Immunofunctional Assay in Comparison to Conventional Assays

Conventional assays for determination of growth hormone (GH) in serum measure immunoreactive molecules of a blood sample. The immunofunctional assay (IFA), on the other hand, is able to determine biologically active molecules. In our study, we evaluated GH determination in children with IFA to compare these data with clinical reliable data of conventional assay systems, since there is only insufficient data concerning the clinical use of IFA in children. The comparison of GH determinations by IFA and two immunoradiometric assays showed different results for the same serum sample. Peak and trough concentration levels determined by these three different assays were always measured at the same time, but absolute GH concentration levels varied. Statistic analysis verified a linear regression of our data and allowed a conversion of data measured by IFA to predict values of the other assays used and vice versa. The traditional cut-off level for the diagnosis of GH deficiency of 10 ng/ml was based originally on results of polyclonal radioimmunoassays. This internationally applied cut-off level has been converted based on the regression analysis for prediction of this study and we found the 95% confidence interval on the mean measurements by IFA to be between 3.11 and 3.28 ng/ml.

Growth hormone treatment of non-growth hormone-deficient growth disorders

Although a large body of data on efficacy and safety of growth hormone (GH) treatment for various non-growth hormone-deficient (GHD) growth disorders has accumulated from a combination of clinical trial and postmarketing sources in the last 20 years or more, there remain limitations. Clinical trial data have the advantage of direct comparison of well-matched, randomized patient groups receiving treatment (or not) under comparable conditions and, as such, provide the highest quality evidence of efficacy. Clinical trials, however, are typically too small for any statistically valid assessment for safety, which is more comprehensively addressed using postmarketing data. Consequently, while the efficacy of GH treatment in children with non-GHD growth disorders has been solidly established and, based on the combination of the rigor of the clinical trial data and numerical power of the postmarketing data, no major concerns exist regarding safety, additional long-term data are required.

Assessment of serum IGF-I concentrations in the diagnosis of isolated childhood-onset GH deficiency: a proposal of the Italian Society for Pediatric Endocrinology and Diabetes (SIEDP/ISPED)

The diagnosis of GH deficiency (GHD) is based on the measurement of peak GH responses to pharmacological stimuli. Pharmacological stimuli, however, lack precision, accuracy, are not reproducible, are invasive, non-physiological and some may even be hazardous. Furthermore, different GH commercial assays used to measure GH in serum yield results that may differ considerably. In contrast to GH, IGF-I can be measured on a single, randomly-obtained blood sample. A review of the available data indicates that IGF-I measurement in the diagnosis of childhood-onset isolated GHD has a specificity of up to 100%, with a sensitivity ranging from about 70 to 90%. We suggest an algorithm in which circulating levels of IGF-I together with the evaluation of auxological data, such as growth rate and growth, may be used to assess the likelihood of GHD in pre-pubertal children.

Transdermal estradiol priming during clonidine stimulation test in non-growth hormone deficient children with short stature: a pilot study

The diagnosis of growth hormone (GH) deficiency is strongly influenced by age, body mass index and presence of gonadal steroids. Priming with oral estradiol (E2) is one possible way to overcome the impact of variable levels of sex steroids. We describe the effects of transdermal estradiol (E2-t) priming on GH response after clonidine stimulation in prepubertal children with familial short stature (group 1, n = 12) or constitutional growth delay (group 2, n = 22). All patients underwent a clonidine test (0.1 mg/m2, p.o.) followed by a clonidine plus E2-t test (50 microg/day) with a 7-day interval. Before E2-t, basal GH and insulin-like growth factor-I (IGF-I) values were similar in the two groups. After E2-t priming, basal GH was significantly higher only in group 2. When compared with group 1, patients from group 2 had a significant increase of GH peak response when submitted to E2-t. The number of patients in both groups with adequate GH peak response was higher after E2-t priming. We conclude that E2-t priming is able to increase GH peak response after clonidine stimulation and also improves the accuracy of the clonidine test in the diagnosis of GH deficiency. Compared to oral administration, E2-t delivery can prevent liver toxicity, providing a more physiological mechanism of GH secretion.

A brief review of the use and utility of growth hormone stimulation testing in the NCGS: do we need to do provocative GH testing?

True growth hormone deficiency (GHD) in childhood, while rare, has major clinical consequences. GHD is often associated with other pituitary hormone deficiencies, so these children may require multiple hormonal replacement and close clinical follow-up to optimize their outcome. Growth hormone stimulation testing (GHST), as currently conducted, is not a reliable diagnostic tool. Both changes in growth hormone assay methodologies and increases in the diagnostic threshold contribute to the incorrect labeling of a substantial proportion of normal children as having idiopathic GHD. Fortunately, newer imaging technologies and laboratory tests form a more rational basis to diagnose true GHD. The use of GHST among GH-naive subjects (<20 years of age) enrolled in the National Cooperative Growth Study has declined over the past two decades, from a high of 89% between 1987 and 1989 to only 52% in 2002. Given that GH stimulation testing does not meaningfully aid in distinguishing those few children with true growth hormone deficiency from the much more common short normal child and that alternatives are now available, it is time to discontinue the routine use of GHST in children.

Human chorionic gonadotropin therapy in adolescent boys with constitutional delayed puberty vs those with beta-thalassemia major

We studied 12 adolescent boys with beta-thalassemia major and delayed puberty (age, 15.8 +/- 1 years) with Tanner I sexual development treated with a long-term low-transfusion regimen. Ten nonthalassemic adolescents (> 14 years) with constitutional delay of growth and puberty (CDGP) served as controls. Auxologic parameters and testicular size were measured, and bone age was determined. Measurement of basal gonadotropin (luteinizing hormone [LH] and follicle-stimulating hormone [FSH]) and testosterone (T) levels taken at 8 am revealed prepubertal levels in both groups of patients. Human chorionic gonadotropin (hCG, 2500 U/m(2)) was injected intramuscularly twice weekly for 6 months, and anthropometric data, testicular diameter, and serum T concentrations were remeasured after 1 and 6 months. The testicular diameter after 6 month of hCG therapy was significantly correlated with the testicular diameter and T level after 1 month of therapy (r = 0.93 and 0.39, respectively, P < .01). After 6 months of hCG therapy, the mean growth velocity (GV) increased from 4.1 to 8.6 cm/y in thalassemic patients and from 4.6 to 10.3 cm/y in those with CDGP during hCG therapy. In thalassemic boys, the mean T concentration increased from 0.93 to 2.7 nmol/L (mean increase = 1.8 nmol/L) vs an increase from 0.47 to 4.81 nmol/L (mean increase = 4.32 nmol/L) in those with CDGP. All adolescents with CDGP, but only 7 the 12 thalassemic adolescents, had T secretion above 2 nmol/L after 6 months of hCG therapy and maintained their growth and pubertal development for a year after stopping hCG. The 5 thalassemic patients with defective T secretion after hCG therapy had significantly higher ferritin level (1985 +/- 658 ng/mL) vs the other 7 patients (1100 +/- 425 ng/mL). These findings denoted significant testicular dysfunction in those patients with higher iron overload (testicular siderosis). Statural GV was significantly correlated with insulin-like growth factor 1 (IGF-1) concentrations and testicular diameter after hCG therapy (r = 0.5 and 0.43 respectively, P < .001). In summary, hCG therapy was effective in treating 7 of 12 (58%) of thalassemic adolescents with delayed puberty. In the rest of patients (5/12, 46%) with significantly higher iron overload, hCG therapy failed to stimulate testicular growth and adequate T. Proper iron chelation appears to protect against testicular dysfunction. In the first group of patients, hCG therapy can be used for the treatment of their hypogonadism, whereas T replacement remains the therapy of choice for the second group.

Is growth hormone stimulation testing in children still appropriate?

The diagnosis of growth hormone deficiency (GHD) historically has relied on measurement of growth hormone (GH) concentrations following stimulation, usually with a non-physiologic provocative agent. Despite the use of more specific GH assays, the peak concentration of GH below which a child is considered GH deficient has risen. We examine the pitfalls associated with GH stimulation tests, specifically, the lack of reliability and accuracy of these tests, and their inability to predict who will benefit from GH therapy. We recommend that GH stimulation tests no longer routinely be used for the diagnosis of GHD in children.

Growth hormone secretory pattern and response to treatment in children with short stature followed to adult height

OBJECTIVE

To compare the relative utility of GH stimulation tests and assays of spontaneous GH secretion as predictors of change in height standard deviation score at the end of GH treatment in children with short stature.

PATIENTS AND METHODS

We retrospectively studied 116 children (67 boys and 49 girls) with subnormal growth rates and short stature, defined as a height of more than 2SD below the mean for age and sex. The patients were classified according to their pattern of findings on baseline pharmacological GH stimulation tests and a 12-h assay of nocturnal spontaneous GH secretion. Twenty-eight patients (24%) had normal hormone levels by both methods (group I); 14 (12%) had normal levels by stimulation tests but subnormal levels by the physiological assay (group II); 48 (41%) had subnormal levels on pharmacological stimulation, with normal physiologic levels (group III); and 26 (22%) had subnormal levels by both methods (group IV). All children in groups II and IV, and 27 in group III, designated IIIb, were treated with recombinant GH at 0.7 U (0.23 mg/kg) of body weight per week. GH secretory patterns were related to final height SD scores and other growth parameters, after the patients had attained their adult stature 6.7 +/- 2.2 years (SD) after GH evaluation.

RESULTS

The five groups were similar with respect to mean baseline height SD scores for chronological as well as bone age. Whether assessed as absolute or parentally adjusted (relative) values, mean gains in height SD scores were significantly greater in treated patients with physiological hormone deficiency (groups II and IV) than in those with normal hormone levels (group I, untreated controls). Relative height gains were 1.03 +/- 1.45 cm (6.6 +/- 9.28 cm) and 1.85 +/- 1.21 cm (SDS; 11.8 +/- 7.74 cm) in groups II and IV respectively, compared with only 0.11 +/- 0.42 cm (0.7 +/- 2.68 cm) in group I (P < 0.01 and P < 0.001). GH treatment failed to improve either the absolute or parentally adjusted final height of patients with GH deficiency by stimulation tests but normal levels by physiological assay.

CONCLUSION

Long-term administration of GH to short children with normal spontaneous GH secretion is not associated with an appreciable increase in adult height.

Neuroendocrine facets of human puberty

The unfolding of pubertal growth and maturation entails multisystem collaboration. Most notably, the outflow of gonadotropins and growth hormone (GH) proceeds both independently and jointly. The current update highlights this unique dependency in the human.

Growth hormone therapy

Since 1958 growth hormone (GH) has been used as substitution treatment for children with GH deficiency. At present, it is clear that a dose of 0.23 mg/kg/week can lead to a final height close to target height, but in view of the wide inter-individual variation, alternative regimens based on invidualizing the dosage with the help of prediction models are being investigated. The best strategy during puberty (increase the dosage, delay puberty) is still uncertain. The value of GH in idiopathic short stature is still heavily debated, although the average final height gain on 0.33 mg/kg/week is 5-7 cm. GH is efficacious in short stature due to chronic renal failure and Prader-Willi syndrome. In other conditions insufficient data are available. There are few side-effects.

Results of early reevaluation of growth hormone secretion in short children with apparent growth hormone deficiency

OBJECTIVE

To test the hypothesis that normalization of the growth hormone (GH) response to stimulation in patients with GH deficiency (GHD) and normal magnetic resonance imaging (MRI) of the hypothalamic-pituitary area might occur earlier than at attainment of final height.

STUDY DESIGN

Prepubertal children with short stature (21 boys and 12 girls; age, 5.2-10 years), in whom a diagnosis of GHD was based on a GH response <10 microg/L after 2 pharmacologic tests (clonidine, arginine, or insulin hypoglycemia), and normal MRI of the hypothalamic-pituitary area were studied. After 1 to 6 months, all children underwent reevaluation of GH secretion by means of one of the provocative tests previously used. During that time, none of the children received GH therapy or entered puberty.

RESULTS

A GH response > or =10 microg/L after retesting was found in 28 patients, and a GH response <10 microg/L was found in 5. In 9 patients, the peak GH response at diagnosis was <7 microg/L to both tests used. In 8, the GH response at retesting was > or =10 microg/L and was 9.0 microg/L in the remaining child.

CONCLUSIONS

We suggest that patients with pathologic GH responses to provocative tests but normal MRI should be reevaluated and followed up before a diagnosis of GHD is firmly established.

Growth hormone and sex steroids. Interactions in puberty

Dynamic interactions among growth hormone, IGF-1, and sex steroidal hormones have a major role in the achievement of full height potential and the body composition changes in adolescence. Testosterone and estrogen affect the growth hormone neuroendocrine rhythms, and growth hormone, in turn, potentiates many of the metabolic actions of the sex steroids. Leptin is also thought to have a key regulatory role in the process of sexual development in the child, but the precise nature of these interactions is unclear. The targeted replacement of hormonal deficiencies in puberty and manipulation of the timing of pubertal maturation have resulted in better strategies to treat profoundly short children during this period; however, more research is needed to determine the consequences of such approaches in aspects of metabolism other than linear growth.