The use of a commercially available somatomedin-C radioimmunoassay in patients with disorders of growth

Use of the Growth Hormone Stimulation Test Result in the Management of Patients With a Short Stature

Introduction A proportionate short stature (SS) assessment involves the documentation of normal growth hormone secretion via a growth hormone (GH) stimulation test. All available GH stimulation tests have some disadvantages. The decision to initiate GH therapy is dependent on multiple factors, including the GH stimulation test result. However, many patients receive GH therapy, even if they have a normal GH stimulation test result, with the indication of a presumed idiopathic SS. Objective In this study, we investigated the use of the GH stimulation test result in initiating GH therapy. Method A cross-sectional study was conducted with patients diagnosed with proportionate SS. Age, gender, insulin-like growth factor 1 (IGF-1) level, and GH stimulation test results were collected retrospectively from the electronic medical records. The main outcome variable was the decision related to prescribing GH therapy. Results A total of 286 patient charts were reviewed, and the majority (n = 201, 64.6%) were male. For just less than half (n = 136, 47.6%), the result of the GH stimulation test was ≥ 10 ng/mL, in a small proportion (n = 53, 18.5%) the result was < 5 ng/mL, and for the rest of the cohort, the result was 5.0 - 9.9 ng/mL. The majority (n = 219, 70.4%) received GH therapy, irrespective of the GH stimulation test result. The odds ratio (OR) for GH treatment was 3.9 (CI: 1.79 - 8.49) and 3.0 (CI: 1.21 - 7.42) for patients with a result < 5 ng/mL and 5.0 - 9.9 ng/mL, respectively, compared to the group with a result of ≥ 10 ng/mL. Conclusion GH therapy is frequently prescribed for patients with SS, irrespective of the GH stimulation test result. However, the group with SS with a result of < 9.9 ng/mL was more likely to receive GH therapy. The question of whether a GH stimulation test is required, in the context of SS, is debatable.

Diagnostic value of serum IGF-1 and IGFBP-3 in growth hormone deficiency: a systematic review with meta-analysis

Serum insulin-like growth factor-1 (IGF-1) and insulin-like growth factor binding protein-3 (IGFBP-3) are conventionally considered available for the diagnosis of growth hormone deficiency (GHD), but the results about their diagnostic values are inconsistent among some recent epidemiological studies. The aim of this study is to assess the diagnostic values of serum IGF-1 and IGFBP-3 for GHD by conducting a systematic review and meta-analysis. Studies on serum IGF-1 and IGFBP-3 used in GHD diagnosis were systematically searched from databases PubMed, EMBASE, and CNKI (up to December 2013). Characteristics of the studies and data were independently collected according to the inclusion criteria by two authors. The quality of included studies was assessed using quality assessment of diagnostic accuracy studies (QUADAS). Both sensitivity (SEN) and specificity (SPE) of IGF-1 and IGFBP-3 in GHD diagnosis were estimated on statistical software Meta-DiSc and Stata. A total of 12 studies were included for the final analysis. IGF-1 had SEN of 0.66, SPE of 0.69, positive likelihood ratio (PLR) of 2.48, negative likelihood ratio (NLR) of 0.51, area under the summary receiver operating characteristic curve (SROC) of 0.78, and Q* value of 0.72. Serum IGFBP-3 had SEN of 0.50, SPE of 0.79, PLR of 2.69, NLR of 0.64, area under SROC of 0.80, and Q* value of 0.73.

CONCLUSION

Serum IGF-1 and IGFBP-3 are useful for the diagnosis of GHD and can be utilized as auxiliary diagnosis indexes for provocative test.

Does plasma IGF-BP3 measurement contribute to the diagnosis of growth hormone deficiency in children?

OBJECTIVE

To audit the contribution of plasma IGF-PB3 measurement to the diagnosis of growth hormone deficiency (GHD) in children.

POPULATION AND METHODS

Retrospective case study including boys and girls aged 0 to 18 years who attended our paediatric endocrinology clinic for short stature and/or post-irradiation follow-up, and had at least one GH provocative testing. Children with hypothyroidism, Laron or Kowarski syndromes, severe malnutrition, chronic renal failure and liver failure were excluded.

RESULTS

Fifty-eight children were enrolled and grouped as GHD [+] (19 cases) and GDH [-] (39 cases). IGF-I and IGF-BP3 assay was carried out in 88% and 62% cases respectively, both groups were comparable for age, sex, BMI, target height, pubertal stage and bone age. There was a significant difference in peak GH between GDH [-] and GHD [+] groups (41.8 mUI/L ± 21.7 versus 11.5 ± 5.9 mUI/L, P<0.00001, respectively). No difference was found between groups with regards to IGF-I Z-scores and IGF-BP3 Z-scores. There was, however, a positive correlation between IGF-I Z-scores and IGF-BP3 Z-scores (r=0.50; P<0.0016). IGF-BP3 measurement could not differentiate between GHD [+] and GHD [-] groups.

CONCLUSIONS

Measurement of plasma IGF-BP3 level contributes poorly to the diagnosis of GHD. We do not recommend it in routine use.

Are IGF-I and IGF-BP3 useful for diagnosing growth hormone deficiency in children of short stature?

BACKGROUND

The diagnosis of growth hormone deficiency (GHD) is based on clinical and auxological characteristics combined with the results of growth hormone provocation tests.

AIM

To evaluate the utility of IGF-I and IGF-BP3 serum levels in the diagnosis of GHD among children of short stature.

SUBJECTS/METHODS

We recruited 207 short pre-pubertal children and divided them into two groups. One group consisted of 70 children (mean age 7.93 +/- 2.35 SD) with a growth hormone (GH) response on two provocative tests of < or = 8 ng/ml, while the other group contained 137 children (mean age 7.92 +/- 2.11 SD) with a peak GH value of > 8 ng/ml. Serum IGF-1 and IGF-BP3 levels were determined in the two groups.

RESULTS

The difference in serum IGF-I between the two groups was not significant (p= 0.26), while the difference in IGF-BP3 between the two groups was statistically significant (p= 0.004). The performance of serum IGF-1 and IGF-BP3 as a diagnostic tool, expressed as AUC by ROC analyses, was quite low.

CONCLUSION

Neither IGF-I nor IGF-BP3 are an adequate substitute for the stimulus test in the diagnosis of growth hormone deficiency among children of short stature.

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.

The use of insulin-like growth factor 1 reference values for the diagnosis of growth hormone deficiency in prepubertal children

OBJECTIVE

This study was done to determine whether the use of reference values obtained in children with idiopathic short stature (ISS) improved the clinical value of serum insulin-like growth factor I (IGF-1) as a tool for diagnosing GH deficiency (GHD) in prepubertal children.

PATIENTS AND METHODS

Serum IGF-1 was measured with a new IRMA kit (IGFI-RIA CT, Cis Bio, Gif sur Yvette, France) in 168 prepubertal normal children and in prepubertal children with ISS (n = 68), organic GHD due to a craniopharyngioma (oGHD, n = 15) and permanent idiopathic GHD (iGHD, n = 28).

RESULTS

IGF-1 was lower (P < 0.001) in iGHD than in either ISS or oGHD and was below the fifth percentile of the normal range in 29/68 ISS (43%), 8/15 oGHD (53%) and 28/28 (100%) iGHD patients. Three oGHD (20%) and two iGHD (7%) patients had a serum IGF-1 below the fifth percentile of the normal group but above the fifth percentile of the ISS group. Thus, a serum IGF-1 below the fifth percentile of the normal group distinguished between normal children and iGHD with 100% sensitivity, between normal and oGHD with 53% sensitivity and between normal and all GHD (idiopathic + organic) with 84% sensitivity; the overall specificity was only 57%. Conversely, a serum IGF-1 below the fifth percentile of the ISS population distinguished between ISS and iGHD with 93% sensitivity, between ISS and oGHD with 33% sensitivity and between ISS and all GHD with 72% sensitivity; the overall specificity was then 95%.

CONCLUSIONS

A serum IGF-1 within the normal range virtually excludes idiopathic GHD but does not rule out organic GHD, whereas an IGF-1 below the ISS range is strongly in favour of GHD, after exclusion of poor nutritional status and/or liver disease. An IGF-1 below the normal range but in the idiopathic short stature range gives no definitive conclusion even when it is associated with a low GH peak. Thus, whereas reference values obtained in normal children must be used to interpret serum IGF-1 in short prepubertal children, reference data obtained in idiopathic short stature children should also be taken into account.

Biochemical tests in the diagnosis of childhood growth hormone deficiency

GH stimulation tests are widely used in the diagnosis of GH deficiency (GHD), although they are associated with a high false positive rate. We have examined, therefore, the performance of other tests of the GH axis [urinary GH excretion, serum insulin-like growth factor I(IGF-I), and IGF-binding protein-3 (IGFBP-3) levels] compared with GH stimulation tests in identifying children defined clinically as GH deficient. Group I comprised 60 children (mean age, 10.3 +/- 4.8 yr) whose diagnosis of GHD was based on a medical history indicative of pituitary dysfunction (n = 43) or on the typical phenotypic features and appropriate auxological characteristics of isolated GHD (n = 17). Group II comprised 110 short children (mean age, 9.8 +/- 4 yr) in whom GHD was not suspected, but needed exclusion. The best sensitivity for a single GH test was 85% at a peak GH cut-off level of 10 ng/mL, whereas the best specificity was 92% at 5 ng/mL. The sensitivities of IGF-I, IGFBP-3, and urinary GH, using a cut-off of -2 SD score were poor at 34%, 22%, and 25%, respectively, with specificities of 72%, 92%, and 76% respectively. Only 2 of 21 pubertal children in group I and none of the 27 subjects with radiation-induced GHD had an IGFBP-3 SD score less than -1.5. We devised a scoring system based on the positive predictive value of each test, incorporating data from the GH test and the IGF-I and IGFBP-3 levels. A specificity of 94% could be achieved with a score of 10 or more (maximum 17) (sensitivity 34%). The latter could not be improved above 81% with a score of 5 points or more (specificity, 69%). A high score was, therefore, highly indicative of GHD, but was achieved by few patients. A normal IGFBP-3 level, however, did not exclude GHD, particularly in patients with radiation-induced GHD and those in puberty. A GH test with a peak level more than 10 ng/mL was the most useful single investigation to exclude a diagnosis of GHD.

Prediction of the outcome of growth hormone provocative testing in short children by measurement of serum levels of insulin-like growth factor I and insulin-like growth factor binding protein 3

Serum levels of insulin-like growth factor I (IGF-I) and insulin-like growth factor binding protein 3 (IGFBP-3) reflect the secretion of endogenous growth hormone (GH) in healthy children and exhibit little diurnal variation, which makes them potential candidates for screening of GH deficiency (GHD). We evaluated serum IGF-I and IGFBP-3 levels in relation to the outcome of GH provocative testing in 203 children and adolescents (111 boys and 92 girls) in whom GHD was suspected. A total of 1030 children served as control subjects. In children less than 10 years of age, IGF-I levels were below the cutoff limit in 8 of 15 children with GHD (sensitivity 53.3%) and above the cutoff limit in 47 of 48 children with a normal GH response (specificity 97.9%). Similarly, IGFBP-3 levels were below the cutoff limit in 9 of 15 children with GHD (sensitivity 60%) and above the cutoff limit in 47 of 48 children with a normal GH response (specificity 97.9%). Consequently the predictive value of a positive test result in prepubertal children was 88.8% for IGF-I and 90% for IGFBP-3. In children and adolescents between 10 and 20 years of age, IGF-I levels were below the cutoff limit in 34 of 46 children with GHD (sensitivity 73.9%) and above the cutoff limit in 63 of 94 children with normal GH response (specificity 67%). IGFBP-3 levels were below the cutoff limit in 26 of 46 children with GHD (sensitivity 56.5%) and above the cutoff limit in 74 of 94 children with a normal GH response (specificity 78.7%). Accordingly the positive predictive value and in 10- to 20-year-old children was 52.3% for IGF-I and 56.5% for IGFBP-3. Combination use of IGF-I and IGFBP-3 gave additional diagnostic information. We conclude that a subnormal IGF-I level, and especially a subnormal IGFBP-3 level, are highly predictive of a subnormal GH response to a provocative test in prepubertal children in whom GHD is suspected. On the other hand, a normal IGF-I or IGFBP-3 level does not exclude GHD. The predictive value of IGF-I and IGFBP-3 in pubertal children is diminished in comparison with that in prepubertal children. We believe that IGF-I and IGFBP-3 are valuable tools in the evaluation of childhood GHD.

Evaluating the child with short stature

Short stature is a common pediatric problem that requires us to decide whether a child's small size represents only normal variation or indicates the presence of an underlying disease. In a population of children two standard deviations (SD) below the mean for height (below the third percentile), about 20 per cent may be expected to have pathologic short stature with the remaining 80 per cent about equally divided between familial short stature and constitutional growth delay. In contrast, most children three SD below the mean for height have pathologic short stature. Set forth in this article is an orderly approach to identify normal variants of short stature and to investigate the causes of pathologic short stature.

An attempt to assess the replacement dose of human growth hormone in the treatment of growth hormone deficient children

In 25 patients with hGH deficiency, who had been treated long-term with hGH, the mode of hGH administration was switched from the conventional method (0.3-0.5 IU/kg/week, in two or three divided doses, intramuscularly) to daily subcutaneous injection at 1900-2100 hours with a dose of 0.46 +/- 0.07 IU/kg/week (equivalent to 14.7 +/- 2.0 IU/m2/week). After 1-3 months of this new mode of hGH administration, blood and urine were sampled at 0900 hours after overnight fasting. Blood glucose, plasma insulin, plasma IGF-1 and plasma total IGF (after extraction) were analysed in blood samples. IGF-1 and hGH were measured in urine samples. These measurements indicated that the dose studied was close to a replacement one, but might be slightly higher than the exact replacement dose.

Testing with growth hormone-releasing factor (GRF(1-29)NH2) and somatomedin C measurements for the evaluation of growth hormone deficiency

Growth hormone (GH) responses to GRF (1 microgram/kg BW i.v.) were investigated. Comparison between GRF(1-40) and GRF(1-29)NH2 in 11 young adult volunteers gave identical results. One hundred and thirty-one children and adolescents (45 with idiopathic GHD) were tested with GRF (1-29)NH2. The maximal GH levels (max GH) in response to GRF during the 120 min test period were found suitable to characterize the response. In cases without GHD no correlation to age, sex and pubertal development was observed. A maximal GH level of above 10 ng/ml was found to be normal. In 3 out of 86 children without GHD (one with Turner syndrome; two with simple obesity) max GH fell short of 10 ng/ml, while 11 of 45 cases with GHD exceeded this margin. In GHD, max GH was inversely correlated with age. There was no difference in max GH between groups with or without perinatal pathology as a presumed cause of GHD. GH levels to GRF were positively correlated with maximal GH level during sleep in GHD, but not correlated with responses seen to insulin or arginine. The value of GRF testing for the confirmation of GHD is discussed in the light of other GH stimulatory tests and basal somatomedin C measurements. It is suggested that the combination of testing with GRF and the determination of a basal SmC level offers a safe and convenient way to diagnose GHD in clinically suspected cases, though in some cases further diagnostic tests may be needed.

Insulin-like growth factors I and II in evaluation of growth retardation

Plasma samples from 68 growth hormone (GH)-deficient children (provocative serum GH level less than 7 ng/ml), 44 normal short children, and 197 children with normal height were assayed by specific radioimmunoassays for the somatomedin peptides, insulin-like growth factors (IGF)-I and -II. Eighteen percent of the GH-deficient children had IGF-I levels within the normal range for age, whereas 32% of normal short children had low IGF-I levels. Low IGF-II levels were found in 52% of GH-deficient children, but also in 35% of normal short children. However, only 4% of GH-deficient children had normal plasma levels of both IGF-I and IGF-II. Furthermore, only 0.5% of normal children and 11% of normal short children had low plasma levels of both IGF-I and IGF-II. We conclude that plasma levels of either IGF-I or IGF-II overlap in GH-deficient and normal short children, but that the combination of radioimmunoassays may permit better discrimination among normal, normal short, and GH-deficient children.

Growth hormone neurosecretory dysfunction

The basis for understanding clinical disorders in the neuroregulation of GH secretion is derived from the complexity of the CNS-hypothalamic-pituitary axis. Studies in animals and humans demonstrate an anatomic, physiological and pharmacological evidence for neurosecretory control over GH secretion including neurohormones (GRH, somatostatin), neurotransmitters (dopaminergic, adrenergic, cholinergic, serotonergic, histaminergic, GABAergic), and neuropeptides (gut hormones, opioids, CRH, TRH, etc). The observation of a defect in the neuroregulatory control of GH secretion in CNS-irradiated humans and animals led to the hypothesis of a disorder in neurosecretion, GHND, as a cause for short stature. We speculate that in this heterogeneous group of children a disruption in the neurotransmitter-neurohormonal functional pathway could modify secretion ultimately expressed as poor growth velocity and short stature.

Stepwise evaluation of the short child. With comments on the status of growth hormone therapy

The role of the primary care physician in evaluating short children is to select those children with true growth failure by careful documentation of height measurements. A directed history and physical examination and limited laboratory testing should identify children with nutritional, structural, or inflammatory causes of poor growth and suggest specific therapy. In those few children with growth hormone deficiency, more complicated and expensive testing and therapy are necessary.

Investigation of hypothalamic-pituitary disease

It can be readily appreciated from the preceding discussion that many endocrine and non-endocrine tests are available for the evaluation of patients with suspected hypothalamic-pituitary disease. The endocrine evaluation of these subjects should be tailored according to the type and extent of pathology suspected (see Tables 2 and 3). For patients with pituitary adenomas and clinical features of hyperpituitarism, such as hyperprolactinaemia, Cushing's disease or acromegaly, the initial tests should be directed at the hormone whose excess is suspected. For example, a glucose suppression test for acromegaly or dexamethasone suppression test for Cushing's disease should be performed early in the evaluation. The possibility of deficiencies of the other pituitary hormones should then be addressed in patients with secretory tumours, but initially in those with apparent non-functioning adenomas. In patients with large macroadenomas pituitary hormone deficiencies are almost invariable with GH and FSH/LH being the most commonly affected, followed by TSH and ACTH in that order (Snyder et al, 1979a; Valenta et al, 1982). Basal thyroid function tests, serum oestradiol or testosterone, and basal gonodotrophins should be routinely obtained in patients with macroadenomas. Additionally, the integrity of the pituitary-adrenal axis should be determined and an overnight water deprivation test for assessment of neurohypophyseal function is also recommended. GH stimulation testing is valuable as a test of pituitary function in patients with suspected pituitary tumours since GH reserve is lost very early in the development of hypopituitarism. Evaluation of the pituitary-thyroid axis with TRH or the pituitary gonadal axis with LHRH generally provides limited additional information of diagnostic value in individual patients with macroadenomas. However, the 'paradoxical' responses to TRH and LHRH may be useful as a biological marker following therapy in patients with GH- or ACTH-secreting tumours. In patients with microadenomas, pituitary hormone deficiencies are uncommon (Valenta et al, 1982). Despite this observation, it may be beneficial to determine basal thyroid levels, gonadotrophin levels, serum testosterone or oestradiol levels, and the response to an overnight metyrapone test in such patients to provide a baseline for future care.(ABSTRACT TRUNCATED AT 400 WORDS)

Short stature and celiac disease: a relationship to consider even in patients with no gastrointestinal tract symptoms

To determine the incidence of celiac disease in a group of nonselected children with short stature, duodenal biopsy was performed in 60 unselected children with short stature (below third centile) and absence of gastrointestinal tract symptoms. Examination revealed probable celiac disease in five children (8.3%). Analysis of the results of other tests that might possibly be considered as alternatives to biopsy (e.g., xylose test, antireticulin antibodies, gastrointestinal tract symptoms in the first two years of life, bone age, serum iron, iron load, triglyceride load) led us to conclude that no test or clinical measurement could have allowed us 100% certainty in making the correct diagnosis. None of the children with celiac disease had growth hormone deficiency. We conclude that asymptomatic celiac disease represents a cause of short stature that cannot be ignored, and that only by intestinal biopsy can all such patients be identified.

Growth hormone treatment for short stature

Fifteen short but otherwise normal children, 4.3 to 15.5 years old, with heights greater than 3 S.D. below the mean value for age, growth rates less than or equal to 5.0 cm per year, and normal serum levels of immunoreactive growth hormone in response to provocative stimuli (peak greater than or equal to 10 ng per milliliter) were treated with intramuscular injections of pituitary growth hormone (0.1 U per kilogram) three times weekly for six months, as were 14 children with documented growth hormone deficiency. In all the latter children growth rate increased by more tan 2.0 cm per year during treatment. In 6 of the 14 short normal children who remained prepubertal, growth rate also increased, by 2.2 to 4.2 cm per year during treatment; four of these children had normal base-line serum somatomedin C concentrations. In both short normal children and children with growth hormone deficiency, the increment in serum somatomedin C concentrations after 4 or 10 daily injections of growth hormone correlated with bone age but not with later growth or growth hormone levels. Among the short normal children, those who responded to growth hormone were younger and had a greater delay in bone age and a slower pretreatment growth rate than the nonresponders. These observations suggest that a dose of growth hormone comparable to that used for the treatment of hypopituitarism increases growth rate in some short normal children.