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

Impact of body mass index on growth hormone stimulation tests in children and adolescents: a systematic review and meta-analysis

Peak stimulated growth hormone (GH) levels are known to decrease with increasing body mass index (BMI), possibly leading to overdiagnosis of GH deficiency (GHD) in children with overweight and obesity. However, current guidelines do not guide how to interpret the peak GH values of these children. This systematic review and meta-analysis aimed to study the effect of the BMI standard deviation score (SDS) on stimulated peak GH values in children, to identify potential moderators of this association, and to quantify the extent to which peak GH values in children with obesity are decreased. This systematic review was performed by the PRISMA guidelines. Medline, Embase, Cochrane, Web of Science, and Google Scholar databases were searched for studies reporting the impact of weight status on peak GH in children. Where possible, individual participant data was extracted and/or obtained from authors. Quality and risk of bias were evaluated using the Scottish Intercollegiate Guidelines Network (SIGN) checklists. The primary outcome was the association between peak GH values and BMI SDS. The pooled correlation coefficient r, 95% confidence interval (CI), and heterogeneity statistic I² were calculated under a multilevel, random-effects model. In addition, exploratory moderator analyses and meta-regressions were performed to investigate the effects of sex, pubertal status, presence of syndromic obesity, mean age and mean BMI SDS on the study level. For the individual participant dataset, linear mixed-models regression analysis was performed with BMI SDS as the predictor and ln(peak GH) as the outcome, accounting for the different studies and GH stimulation agents used. In total, 58 studies were included, providing data on n = 5135 children (576 with individual participant data). Thirty-six (62%) studies had high, 19 (33%) medium, and 3 (5%) low risks of bias. Across all studies, a pooled r of -0.32 (95% CI -0.41 to -0.23, n = 2434 patients from k = 29 subcohorts, I² = 75.2%) was found. In meta-regressions, larger proportions of males included were associated with weaker negative correlations (p = 0.04). Pubertal status, presence of syndromic obesity, mean age, and mean BMI SDS did not moderate the pooled r (all p > 0.05). Individual participant data analysis revealed a beta of -0.123 (95% CI -0.160 to -0.086, p < 0.0001), i.e. per one-point increase in BMI SDS, peak GH decreases by 11.6% (95% CI 8.3-14.8%). To our knowledge, this is the first systematic review and meta-analysis to investigate the impact of BMI SDS on peak GH values in children. It showed a significant negative relationship. Importantly, this relationship was already present in the normal range of BMI SDS and could lead to overdiagnosis of GHD in children with overweight and obesity. With the ever-rising prevalence of pediatric obesity, there is a need for BMI (SDS)-specific cutoff values for GH stimulation tests in children. Based on the evidence from this meta-analysis, we suggest the following weight status-adjusted cutoffs for GH stimulation tests that have cutoffs for children with normal weight of 5, 7, 10, and 20 µg/L: for overweight children: 4.6, 6.5, 9.3, and 18.6 µg/L; and for children with obesity: 4.3, 6.0, 8.6, and 17.3 µg/L.

Functional amyloids in the human body

Amyloids have long been associated with a variety of human degenerative diseases. Discoveries indicate, however, that there are several amyloids that serve functional roles in the human body. These amyloids are involved in a variety of biological processes ranging from storage of peptide hormones to necroptosis of cells. Additionally, there are distinct differences between toxic amyloids and their functional counterparts including kinetics of assembly/disassembly and structural features. This digest article surveys the biological roles of functional amyloids found in the human body, key differences between functional and toxic amyloids, and potential therapeutic applications.

Protein therapeutics: a summary and pharmacological classification

Once a rarely used subset of medical treatments, protein therapeutics have increased dramatically in number and frequency of use since the introduction of the first recombinant protein therapeutic--human insulin--25 years ago. Protein therapeutics already have a significant role in almost every field of medicine, but this role is still only in its infancy. This article overviews some of the key characteristics of protein therapeutics, summarizes the more than 130 protein therapeutics used currently and suggests a new classification of these proteins according to their pharmacological action.

Circulating immunoreactive growth hormone releasing hormone concentrations and growth hormone response to growth hormone releasing hormone in short children

To study the role of peripheral immunoreactive growth hormone releasing hormone (ir-GHRH) concentrations and the GHRH test in the evaluation of growth hormone (GH) secretion in short stature, 46 children with a mean age of 9.4 years (range 1.6-16.3 years) and a mean relative height score of -3.2 SD (range -5.0-2.1 SD) were investigated. The children were divided into prepubertal (n = 35) and pubertal (n = 11) and the prepubertal children further into three groups based on their maximal GH responses to insulin-induced hypoglycaemia (IIH) and clonidine: (1) GH deficient subjects (maximal GH < 10 micrograms/l in both tests); (2) discordant responders (maximal GH < 10 micrograms/l in one test and > or = 10 micrograms/l in the other); and (3) normal responders (maximal GH > or = 10 micrograms/l in both tests). Peripheral ir-GHRH concentrations were measured during the IIH test by radioimmunoassay after purification of plasma samples on Sep-pak cartridges. Among the prepubertal children 10 fell into group 1, 16 into group 2 and 9 into group 3. Children in group 1 were older than those in group 3. There were no significant differences in relative heights and weights or absolute and relative growth velocities between the groups. Subjects in groups 1 and 2 had lower maximal GH responses to GHRH than those in group 3. There were no significant differences in the basal plasma ir-GHRH concentrations between the groups. Nine children (19.6%) had somatotrophs with a poor response to a single dose of exogenous GHRH (maximal GH < 10 micrograms/l).(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of growth hormone secretion and treatment

The secretion of growth hormone (GH) is regulated by a complex system that includes both neurotransmitters and feedback by hormonal and metabolic substrates. Over the last few years it has been recognized that GH release varies over a wide spectrum from deficient to excessive secretion. The diagnosis of GH deficiency is based on a combination of anthropometric and clinical signs on the one hand and an inadequate stimulated and/or spontaneous GH secretion on the other. There is no distinct boundary between deficient and sufficient GH secretion. The cut-off limit for normal GH release is accordingly relative and has increased over the past decade from 5 to 10 micrograms/l. The effect of GH therapy on growth can be evaluated only after treatment for at least 6 months. There is, therefore, an indisputable need for methods that would reflect growth response soon after the start of treatment. There are several promising biochemical candidates, e.g. the aminoterminal propeptide of type III procollagen, the carboxyterminal propeptide of procollagen I and the bone Gla-protein, which may turn out to be useful early indicators of the growth response to long-term GH therapy.

Diagnosis of growth hormone deficiency

Many ways of evaluating the physiological state of hGH secretion exist, some of which have been touched upon and none of which has as yet proven infallible. Apart from important clinical features like history, physical data and growth rate, the diagnosis of altered pituitary function is based on tests and their interpretation. The physician responsible has to be informed on their effectiveness and pitfalls. Results should be interpreted in relation to developmental age (bone age) rather than chronological age. Research is under way to try to facilitate the diagnosis of varying degrees of alterations of hGH secretion. Reliability in predicting the effect of therapy with hGH is the ultimate aim in order to prevent unnecessary cost and disappointment for the patients. With the help of doctors involved in child care, such as physicians at kindergarten or school, it should be possible to start the slow process of investigating growth disorders at an early age.

Diagnostic value of growth hormone-releasing hormone test in children and adolescents with idiopathic growth hormone deficiency

Average growth hormone (GH) peaks following an i.v. growth hormone releasing hormone (GHRH) 1-29 stimulation test were significantly lower in 48 children and adolescents with GH deficiency (GHD) than in 20 age-matched controls (15.2 + 12.7 vs 37.5 + 28.1 ng/ml, 2 P less than 0.001). Twelve patients exhibited a low GH peak (less than 5 ng/ml), 27 demonstrated a normal response (greater than 10 ng/ml) and 9 showed an intermediate rise in plasma GH (5-10 ng/ml). Six of the 12 patients with low GH response to the first GHRH stimulation failed to respond to two other tests immediately before and after a 1 week priming with s.c. GHRH. These subjects with subnormal GH increase at repeat testing had total GHD (TGHD) and multiple pituitary hormone deficiency (MPHD) and had suffered from perinatal distress. On the contrary, 26 of 27 patients with normal GH response to the first test had isolated GHD and only a minority (8/27) had signs of perinatal distress. It is concluded that perinatal injuries primarily damage pituitary structures and that a pituitary defect more probably underlies more severe forms (TGHD and MPHD) of GHD.

Rapid effect of intravenous growth hormone (GH)-releasing hormone 1-44 on plasma GH levels in children

Growth hormone releasing hormone (GHRH)-testing was performed in 24 short normal children (16 male, 8 female). Before and after administration of GHRH1-44 (1 microgram/kg body weight i.v.) blood samples for growth hormone (GH) determination were drawn at -30, 0, 1, 2, 3, 4, 6, 8, 10, 15, 30, 45, 60, and 90 min. Plasma GH increase was apparent 1 min after injection and in 12 patients (7 female) peak plasma GH values were reached within 15 min. In all patients plasma GH levels were greater than 10 ng/ml within the first 8 min following GHRH injection, but in 4 patients this level was not attained when considering only GH values obtained after 15 min. These results demonstrate the capability of the pituitary to rapidly secrete GH in response to GHRH1-44 in children. Therefore, in this age group blood samples for GH determination should be taken earlier when testing with GHRH1-44.