Interpretative difficulties with growth hormone provocative retesting in childhood-onset growth hormone deficiency

The landscape of retesting in childhood-onset idiopathic growth hormone deficiency and its reversibility: a systematic review and meta-analysis

OBJECTIVE

Children diagnosed with idiopathic isolated growth hormone deficiency (IGHD) are frequently observed to no longer be GH-deficient at a later stage of growth as a result of 'GHD reversal'. Reevaluation of GH status by stimulation test is currently incorporated into management guidelines at attainment of final height (FH). Over the past three decades, numerous studies have evaluated reversal rates using different methodologies including crucial parameters like GHD aetiology, GH cut-off and retesting time point, with heterogeneous results. We aimed to systematically analyse the reversibility of childhood-onset IGHD dependent on retesting GH cut-offs and retesting time points.

METHODS

PubMed, Cochrane Library, TRIP database and NHS Evidence were searched for publications investigating the reversibility of IGHD from database initiation to 30 June 2020 following PRISMA recommendations. Study cohorts were pooled according to retesting GH cut-off and time point. Reversal rates were calculated using random-effects models.

RESULTS

Of the 29 studies initially identified, 25 provided sufficient detail for IGHD analysis, resulting in 2030 IGHD patient data. Reversal rates decreased significantly as the retesting GH cut-off increased (P = 0.0013). Pooled (95% CI) reversal rates were 80% (59-92%, n = 227), 73% (62-81%, n = 516) and 55% (41-68%, n = 1287) for cohorts using retesting GH cut-offs of 3-4 ng/mL, 5-6 ng/mL and 7.7-10 ng/mL, respectively. Individuals retested at FH (n = 674) showed a pooled reversal rate of 74% (64-82%) compared to 48% (25-71%) when retested before FH (n = 653).

CONCLUSION

Provided evidence supports reevaluation of current IGHD management guidelines. The high reversal rates should instigate consideration of early retesting.

Response to growth hormone according to provocation test results in idiopathic short stature and idiopathic growth hormone deficiency

PURPOSE

To investigate growth response in children with either idiopathic short stature (ISS) or growth hormone (GH) deficiency (GHD).

METHODS

The data of prepubertal GHD or ISS children treated using recombinant human GH were obtained from the LG Growth Study database. GHD children were further divided into partial and complete GHD groups. Growth response and factors predicting growth response after 1 and 2 years of GH treatment were investigated.

RESULTS

This study included 692 children (98 with ISS, 443 partial GHD, and 151 complete GHD). After 1 year, changes in height standard deviation score (ΔHt-SDS) were 0.78, 0.83, and 0.96 in ISS, partial GHD, and complete GHD, respectively. Height velocity (HV) was 8.72, 9.04, and 9.52 cm/yr in ISS, partial GHD, and complete GHD, respectively. ΔHt-SDS and HV did not differ among the 3 groups. Higher initial body mass index standard deviation score (BMI-SDS) and midparental height standard deviation score (MPH-SDS) were predictors for better growth response after 1 year in ISS and the partial GHD group, respectively. In the complete GHD group, higher Ht-SDS and BMI-SDS predicted better growth response after 1 year. After 2 years of GH treatment, higher BMI-SDS and MPH-SDS predicted a better growth outcome in the partial GHD group, and higher MPH-SDS was a predictor of good growth response in complete GHD.

CONCLUSION

Clinical characteristics and growth response did not differ among groups. Predictors of growth response differed among the 3 groups, and even in the same group, a higher GH dose would be required when poor response is predicted.

The impact of long-term growth hormone treatment on metabolic parameters in Japanese patients with short stature born small for gestational age

BACKGROUND/AIMS

An examination of the effects of up to 260 weeks of growth hormone (GH) therapy on metabolic parameters in Japanese children born small for gestational age (SGA).

METHODS

Data were analysed from a 156-week extension of a 104-week multicentre, randomised, double-blind, parallel-group trial. Sixty-five children born SGA (age 3-<8 years) received 33 μg/kg/day (n = 31, 64.5% male) or 67 μg/kg/day (n = 34, 58.8% male) GH for 260 weeks. Changes in metabolic parameters - glucose, insulin, total cholesterol, low-density lipoprotein cholesterol and high-density lipoprotein cholesterol - were recorded. Alterations in weight, body mass index standard deviation score (BMI SDS) and vital signs were also evaluated.

RESULTS

Over 260 weeks of GH treatment, a positive correlation between Δheight SDS and Δinsulin-like growth factor-I SDS was observed. Insulin and glucose levels were generally unaffected. Favourable changes in lipid profiles were recorded, which were maintained for the study duration. No adverse alterations in weight, BMI SDS or vital signs were noted.

CONCLUSION

Long-term, continuous GH treatment in children born SGA appears to be efficacious, associated with potential benefits for several metabolic parameters and associated with no long-term safety concerns.

Structure and physiological actions of ghrelin

Ghrelin is a gastric peptide hormone, discovered as being the endogenous ligand of growth hormone secretagogue receptor. Ghrelin is a 28 amino acid peptide presenting a unique n-octanoylation modification on its serine in position 3, catalyzed by ghrelin O-acyl transferase. Ghrelin is mainly produced by a subset of stomach cells and also by the hypothalamus, the pituitary, and other tissues. Transcriptional, translational, and posttranslational processes generate ghrelin and ghrelin-related peptides. Homo- and heterodimers of growth hormone secretagogue receptor, and as yet unidentified receptors, are assumed to mediate the biological effects of acyl ghrelin and desacyl ghrelin, respectively. Ghrelin exerts wide physiological actions throughout the body, including growth hormone secretion, appetite and food intake, gastric secretion and gastrointestinal motility, glucose homeostasis, cardiovascular functions, anti-inflammatory functions, reproductive functions, and bone formation. This review focuses on presenting the current understanding of ghrelin and growth hormone secretagogue receptor biology, as well as the main physiological effects of ghrelin.

United States multicenter study of factors predicting the persistence of GH deficiency during the transition period between childhood and adulthood

Background

Many patients with childhood-onset growth hormone (GH) deficiency do not fulfill diagnostic criteria for GH deficiency (GHD) after attainment of adult height and may not require long-term GH treatment. Patients with history of idiopathic GHD (IGHD) pose the greatest management dilemma, as data regarding factors predictive of persistent GHD in this group are lacking.

Objectives

The objective of this study was to assess potential predictors of persistent GHD in a US patient cohort during transition from childhood to adulthood, particularly in patients with history of IGHD.

Methods

We studied 73 US patients with history of childhood-onset GHD screened at 21 US pediatric endocrine centers for a randomized clinical trial of GH replacement after attainment of adult height. The cohort comprised 42 boys/men and 31 girls/women aged14–22 years, who had received ≥1 year of GH treatment and had completed linear growth. The main outcome measures were sensitivity, specificity, positive and negative predictive values (PPV, NPV) of clinical and hormonal factors for persistent GHD (defined a priori in this study as peak GH < 5 μg/L).

Results

For the cohort as a whole, the best predictors of persistent GHD (100% PPV) were history of organic hypothalamic-pituitary disorder or ≥2 additional pituitary hormone deficiencies (PHD). Best predictors of persistent GHD in patients with childhood history of IGHD were standard deviation scores (SDS) for serum insulin-like growth factor binding protein-3 (IGFBP-3) below -2.0, and for insulin-like growth factor-I (IGF-I) below -5.3 (measured ≥6 weeks after completion of GH treatment; PPV 100% for both), and age <4 years at original diagnosis (PPV 89%). IGF-I above -1.6 SDS had 100% NPV.

Conclusions

US patients with an organic cause of childhood-onset GHD or ≥2 additional PHDs may not require GH stimulation testing to reconfirm GHD after completion of childhood treatment. In contrast, patients with idiopathic childhood-onset GHD almost invariably require retesting, as GHD persists in only a minority (those who were very young at initial diagnosis and those who have subnormal IGFBP-3 or extremely low IGF-I after completion of childhood treatment). Subnormal posttreatment IGF-I (<-2.0 SDS) lacked predictive power for persistent GHD, whereas IGF-I > -1.6 SDS was 100% predictive of GH sufficiency.

An approach to constitutional delay of growth and puberty

Constitutional delay of growth and puberty is a transient state of hypogonadotropic hypogonadism associated with prolongation of childhood phase of growth, delayed skeletal maturation, delayed and attenuated pubertal growth spurt, and relatively low insulin-like growth factor-1 secretion. In a considerable number of cases, the final adult height (Ht) does not reach the mid-parental or the predicted adult Ht for the individual, with some degree of disproportionately short trunk. In the pre-pubertal male, testosterone (T) replacement therapy can be used to induce pubertal development, accelerate growth and relieve the psychosocial complaints of the adolescents. However, some issues in the management are still unresolved. These include type, optimal timing, dose and duration of sex steroid treatment and the possible use of adjunctive or alternate therapy including: oxandrolone, aromatase inhibitors and human growth hormone.

Usefulness of magnetic resonance findings of the hypothalamic-pituitary region in the management of short children with growth hormone deficiency: evidence from a longitudinal study

PURPOSE

The purpose of this study is to assess the relationship between magnetic resonance images (MRI) of the hypothalamic-pituitary (H-P) region and response to recombinant human growth hormone (rhGH) treatment in short children with growth hormone deficiency, basing on changes of auxologic parameters, as well as to answer the question if MRI may serve for selecting and monitoring the rhGH responders.

PATIENTS AND METHODS

The study group comprised 85 children treated with rhGH, aged 7.3-18.7 years, followed for the mean period of 3.2 years (range, 2.1-9.5 years). Auxologic parameters (height deficit hSDS, deviation from the mid-parental height hSDS-mpSDS, bone delay index bone age/chronological age ratio (BA/CA)) were assessed before, during and at the end of rhGH treatment; growth velocity was calculated before and during rhGH therapy. Parameters were correlated with the MRI of the H-P region.

RESULTS

Structural anomalies of the H-P region were found in 22 (25.9%) children: empty sella syndrome (ESS) in 12 (14.1%) patients, ectopic posterior pituitary (EPP) in ten (11.8%). Patients' height deficit and their deviation from parental height before rhGH therapy was significantly greater in the EPP group (median hSDS = -3.8; hSDS-mpSDS = -2.5), bone age delay was the greatest in the ESS group (median BA/CA = 0.69), after therapy - in the EPP group (median BA/CA = 0.82). Growth velocity improved in the first year of the rhGH therapy in all groups; however, the most significant acceleration was observed in the EPP group (median delta hSDS = 0.9), then stabilised and was comparable in all groups.

CONCLUSIONS

MRI may be helpful in predicting response to the rhGH treatment, providing midline abnormalities are taken into account.

Pros of priming in the diagnosis of growth hormone deficiency

Priming with sex steroids in stimulation tests for the diagnosis of GHD is still under debate. Most of the data on utility of priming during GH stimulation so far seem to support its use in the diagnosis of GHD in childhood. There is a propensity to treat growth retarded children who test subnormally to stimulation tests with GH. However, some studies analyzing the final height or height gain during GH treatment in such children failed to show any improvement in height. This paper summarizes previous studies on priming to analyze the utility of priming as a valid method to better the diagnostic capacity of the test.

Pharmacological and physiological growth hormone stimulation tests to predict successful GH therapy in children

Although the current use of growth hormone (GH) stimulation tests (GHSTs) is still subject to debate, the tests are widely used to diagnose GH deficiency. This literature review evaluates primarily the sensitivity, specificity and reliability of GHSTs and secondarily their convenience. Single pharmacological tests typically address only a single pathway in the complex physiological regulation of GH secretion and are therefore characterized by lower sensitivity, specificity and reliability than combined pharmacological tests or physiological tests. In spite of the high levels of sensitivity, specificity and reliability, physiological tests require considerably more effort to perform, from the physician as well as from the child. Therefore, a need for an alternative, convenient, physiological GHST still remains. Oral ingestion of dietary protein is convenient in practice and may induce more physiological stimulation of GH secretion, hence may be a promising valuable addition to the existing GHSTs in GH deficiency.

Reevaluation of growth hormone deficiency during and after growth hormone (GH) treatment: diagnostic value of GH tests and IGF-I and IGFBP-3 measurements

Retesting of patients with growth hormone (GH) deficiency (GHD), especially those with idiopathic GHD, has yielded normalization of the results in several studies. The aim of this study was to reevaluate patients diagnosed as GHD at completion or reconfirm the diagnosis before completion of GH treatment by retesting with provocative tests, and to evaluate the value of IGF-I and IGFBP-3 levels in the diagnosis of GHD. Fifty (33 M, 17 F) patients with GHD (peak GH level <0.46 pmol/l (10 ng/ml]) in two pharmacological tests were retested and IGF-I and IGFBP-3 levels measured. The age of the patients at retest was 15.2+/-5.0 yr. Thirteen of 50 patients (26%) normalized their GH secretion. According to the initial diagnosis, 69% of those with partial GHD (peak GH level 0.32-0.46 pmol/l [7-10 ng/ml]), 43% with isolated GHD, 33% idiopathic and 11% of those with complete GHD (peak GH level <0.32 pmol/l [7 ng/ml]) normalized their GH level at retesting. None of the patients with multiple hormone deficiency and none with small pituitary on MRI normalized GH levels at retest. The sensitivities of IGF-I and of IGFBP-3 were 70% and 67%, respectively, and the specificities were 100%, when peak GH cutoff is taken as 0.46 pmol/l (10 ng/ml) for the diagnosis of GHD. The sensitivities of IGF-I and IGFBP-3 increased to 76.5% and 73.5% when the cutoff level for GHD is taken as 0.32 pmol/l (7 ng/ml). Those patients who normalized their GH levels at retest showed a satisfactory height velocity when GH therapy was discontinued. In conclusion, reevaluation of GH status may also be undertaken while patients are still on treatment as well as at completion of treatment, especially in patients with idiopathic, partial and isolated GHD, by retesting and by IGF-I and IGFBP-3 measurements. Lowering the cutoff level of GH peak at pharmacological tests to 0.32 pmol/l (7 ng/ml) will lower the number of false positive results in the diagnosis of GHD.

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.

Short-term growth response to GH treatment and considerations upon the limits of short-term growth predictions

OBJECTIVES

To investigate the impact of short-term growth measurements on predicting the individual growth response to GH treatment, and to elucidate the possible reasons for the limited accuracy of current growth prediction models for GH-treated children.

METHODS

Short-term growth measurements by knemometry and stadiometer in 99 short, GH-treated children (27 girls, 72 boys), aged 10.3 +/- 2.3 years, from the Children's University Hospital, Leipzig, Germany.

RESULTS

GH treatment significantly accelerated the mean height velocity (HV) from 4.3 +/- 1.0 to 8.1 +/- 1.8 cm/year during the first year of treatment, the average height standard deviation score (SDS) shifted by +0.52 SD. The variation in HV also increased, from S(2) = 1.0 before to S(2) = 3.4 cm(2)/year(2) during treatment. Lower leg length (LLL) velocity accelerated from 1.6 +/- 0.7 before treatment to 3.4 +/- 1.0 cm/year during the first 8 weeks of treatment. Four coefficients of correlation appeared clinically meaningful: (1) LLL velocity vs. body HV during the first year of GH treatment (r = 0.87), indicating that GH acts simultaneously on leg and rump growth; (2) early (first 8 weeks) LLL velocity vs. 1-year body HV during treatment, with r = 0.61 (R(2) = 0.38), indicating that 38% of the variation in HV during the first year of treatment is already predictable by an initial 8-week period of knemometry; (3) early (first 8 weeks) LLL velocity vs. 1-year LLL velocity during treatment, with r = 0.63 (R(2) = 0.39), and (4) early (first 8 weeks) LLL velocity vs. later LLL velocity, up to the end of the first year, with r = 0.53 (R(2) = 0.28) indicating that the early response on lower leg growth persists for at least 1 year of GH treatment.

CONCLUSIONS

(1) Thirty-eight percent of the variation in HV during the first year of GH treatment is predictable by an initial 8-week period of knemometry. This parallels early changes in biochemical markers of bone turnover after GH treatment. (2) There is evidence for a baseline variability in HV both in healthy children and in children with growth disorders that make growth prediction difficult.

Growth response to recombinant human growth hormone (GH) in children with idiopathic growth retardation by level of maximum GH peak during GH stimulation tests

Due to their lack of reproducibility, it is unlikely that GH stimulation tests can provide reliable diagnostic information to distinguish partial isolated GH deficiency (GHD) from idiopathic short stature (ISS). We hypothesized that the classical distinction between these groups, essentially based on stimulatory GH peaks, is artificial and that, as a consequence, the average response to GH treatment will not be different between them. The hypothesized lack of prognostic validity of stimulatory GH peaks was studied in 435 prepubertal children with nonorganic growth retardation. Children were categorized as 'severe GHD', 'partial GHD' or 'ISS', if the maximum rise in their serum GH during two GH stimulation tests was 0--10 mU/l, 10--20 mU/l, or >20 mU/l, respectively. Children with 'partial GHD' had short-term (1- and 2-year) and long-term (till final adult height) growth responses similar to those of children with ISS, significantly lower than the response seen in children with 'severe GHD'. In children with stimulatory GH peaks >10 mU/l, including those currently considered partially GH deficient, the maximum GH peak was not a significant determinant of growth response in the short or the long term. In conclusion, 'partial GHD' is ill defined and cannot be distinguished from ISS based on the currently applied auxological or GH stimulation test criteria alone. More research is required for better identification of (all) children who will respond to GH treatment, whether or not GH deficient.

Growth hormone therapy for hypopituitary adults: time for re-appraisal

The advent of the production of large quantities of recombinant growth hormone (GH) has made it possible to have sufficient material to assess its efficacy in adult growth hormone deficiency (GHD). Although some studies have shown that patients who are severely deficient benefit from GH therapy, the spectrum of GHD is broad, and the degree of deficiency at times is very difficult to define. In some cases, benefit is not easily quantified, and some studies have claimed benefits that, although statistically significant, are either not clinically important or are so marginal as to be questionable in terms of cost, difficulty of administration and potential risks. The purpose here is to identify the current problems in the diagnosis of GHD, to discuss the rationale for GH therapy and to assess the potential effects of GHD as well as the benefits of GH therapy in GHD adults. We will include a commentary as to which effects appear more robust than others and which are likely to result in the greatest patient benefit. Finally, some attention will be paid to long-term safety issues that should be monitored to ensure that this medication is safe even for the patients with the greatest need.