Differences in somatomedin-C between short-normal subjects and those of normal height

Biomarkers of GH action in children and adults

Growth hormone (GH) and IGF-I levels in serum are used as biomarkers in the diagnosis and management of GH-related disorders but have not been subject to structured validation. Auxological parameters in children and changes in body composition in adults, as well as metabolic parameters and patient related outcomes are used as clinical and surrogate endpoints. New treatment options, such as long acting GH and GH antagonists, require reevaluation of the currently used biochemical biomarkers. This article will review biomarkers, surrogate endpoints and clinical endpoints related to GH treatment in children and adults as well as in acromegaly.

Insulin-like growth factor-1 as an indicator of nutrition during treatment of adolescent girls with eating disorders

AIM

The use of serum insulin-like growth factor-1 (IGF-1) concentrations as an index of nutrition has been analysed in teenage girls with eating disorders and weight loss.

METHOD

Blood samples for analysis of IGF-1 were obtained at 349 assessments of 302 patients and biweekly during 56 treatment periods in 46 patients. IGF-1 was related to body size, weight loss, degree of leanness (BMI standard deviation score) and rate of weight loss.

RESULTS

At assessment, when most of the girls were on a weight-losing course, serum IGF-1 concentrations were low. Weight loss immediately prior to assessment was the most important predictor of IGF-1. Together with measurements of weight, height, weight loss and BMI standard deviation score the rate of weight loss predicted IGF-1 to 32-55%. During treatment when there was net weight gain, IGF-1 increased in parallel with the BMI standard deviation score, a measure of leanness, and was also influenced by the short-term weight trend.

CONCLUSION

The serum IGF-1 concentration is an indicator of nutritional status in adolescents with eating disorders. It is sensitive to short-term weight changes measured in a clinical setting and could be used at assessment and to monitor nutritional rehabilitation.

Estrogen priming effect on growth hormone (GH) provocative test: a useful tool for the diagnosis of GH deficiency

We have studied the effect of estradiol (E2) on the GH-insulin-like growth factor (GH-IGF) axis in 15 prepubertal GH deficiency (GHD) children and 44 prepubertal or early pubertal children with idiopathic short stature (SS). All of them received a daily dose of micronized E2 (1 or 2 mg) or placebo, for 3 days, before a sequential arginine-clonidine test. In SS children, GH maximal responses were 17.8+/-10.9 on placebo and 27.9+/-14.5 microg/L on estrogen (P < 0.0001). The lower 95% confidence limits for GH maximal response changed from 3.7 microg/L (without E2) to 8.3 microg/L (on E2). In GHD children, no significant stimulatory effect of estrogen on GH levels was observed. After placebo, a cut-off limit of 3.7 microg/L (the lower 95% confidence interval limit) resulted in 73% sensitivity, 95% specificity, and an overall 90% diagnostic efficiency. After E2, a cut-off limit of 8.3 microg/L resulted in a sensitivity of 87%, a specificity of 98%, and a diagnostic efficiency of 95%. After placebo, 68% of SS showed normal IGF-I levels, and the mean did not change on E2 (13.7+/-6.3 vs. 14.3+/-6.8 nmol/L, not significant). In 93% of SS, IGF binding protein (IGFBP)-3 levels were normal during placebo. On E2, mean IGFBP-3 did not change (2.63+/-0.70 vs. 2.70+/-0.70 mg/L, not significant). In 14 of 15 GHD patients, IGF-I values were below normal on placebo, and the mean of the group did not change after E2. During placebo, 13 of 15 GHD children presented low IGFBP-3 values. During E2, there was a small significant increase in IGFBP-3 values (1.06+/-0.58 vs. 1.20+/-0.69 mg/L, P < 0.02). The highest diagnostic efficiencies for IGF-I and IGFBP-3 were observed during placebo (75% and 91%, respectively). We conclude that GH stimulation tests after E2 priming had the highest diagnostic efficiency. Our findings suggest that the effect of estrogen priming on GH stimulated levels, by reducing the number of false nonresponders, might be useful to better discriminate between normal and abnormal GH status in SS children.

Normal plasma levels of IGF binding protein in Perthes' disease. Follow-up of previous report

Plasma levels of insulin-like growth factor binding protein-3 (IGFBP-3) were measured in 55 children with Perthes' disease and 55 age- and sex-matched controls. IGFBP-3 values did not differ between the 2 groups and corresponded well to normal values found by others. The IGF I/IGFBP-3 ratio was reduced during the first 2 years of Perthes' disease. Our findings indicate that low levels of circulating IGF I in Perthes' disease, as we have reported previously, are caused neither by altered concentrations of the principal IGF-binding protein, IGFBP-3, nor by an underlying growth hormone deficiency.

Decreased serum levels of nutritional biochemical indices in healthy children with marginally delayed physical growth

Biochemical markers of nutritional status (albumin, transthyretin, insulin-like growth factor-I and zinc) were measured in slowly growing two- to five-year-old, low-income Parisian children whose weight-for-height or height-for-age z scores (WHZ or HAZ) were between -1 and -2 SD of the NCHS median. The results were compared to controls who were matched for age, sex, and ethnic origin with WHZ and HAZ between -1 and +2 SD. Mean serum levels of transthyretin, albumin and insulin-like growth factor-I and mean plasma zinc concentrations were significantly lower in the growth-impaired children than in the controls (p = 0.002, p = 0.006, p = 0.015, and p = 0.035, respectively). While the height-retarded children had low mean serum insulin-like growth factor-I values, the weight-retarded subjects had decreased levels of albumin, transthyretin and zinc when compared to controls. Lower mean levels of nutritional markers in healthy, slowly growing children suggest that inadequate dietary intakes of zinc, protein and/or energy may result in marginal delays in weight and height gains.

Urinary excretion of human growth hormone in children with short stature: correlation with pituitary secretion of human growth hormone

Thirty-five children with short-stature underwent insulin-loading and sleep tests for assessment of secretion of human growth hormone. Correlations between the levels of human growth hormone in the serum and urine during the tests were examined to elucidate the clinical significance of urinary human growth hormone levels in short children. The concentration and total amount of human growth hormone in the urine correlated significantly with the peak concentration of serum human growth hormone (r = 0.81, p less than 0.001 and r = 0.80, p less than 0.001, respectively) and the integrated concentration of human growth hormone (r = 0.85, p less than 0.001 and r = 0.85, p less than 0.001, respectively) in the insulin-loading test. The concentration and total amount of human growth hormone in the morning urine also correlated significantly with the peak concentration of serum human growth hormone (r = 0.80, p less than 0.001 and r = 0.70, p less than 0.001, respectively) and the integrated concentration of serum human growth hormone (r = 0.80, p less than 0.001 and r = 0.72, p less than 0.001, respectively) in the sleep test. The concentration or total amount of human growth hormone in the urine differed significantly among children with human growth hormone deficiency, those with nonendocrine short stature, and those with normal stature (p less than 0.05). These data suggest that measurement of human growth hormone in the urine may be used to assess secretion of human growth hormone, serving as a screening test for human growth hormone deficiency in children.

Growth hormone evaluation in Duchenne muscular dystrophy

Growth hormone (GH) release with pharmacological tests and sleep test, somatomedin C and auxological features were studied in 10 patients affected by Duchenne Muscular Dystrophy. GH release in these patients seems to be lower than normal; moreover some of them are of short stature without an evident relationship with GH deficit. The possible significance of the data obtained is discussed, particularly in relation to the clinical course of the disease, and to current therapeutic trials with a GH release inhibitor (mazindol).

The advantage of measuring stimulated as compared with spontaneous growth hormone levels in the diagnosis of growth hormone deficiency

To clarify the relative usefulness of measuring stimulated as compared with spontaneous growth hormone levels in the diagnosis of growth hormone deficiency, we studied 54 short prepubertal children--23 with growth hormone deficiency identified by stimulation tests and 31 with idiopathic short stature who had normal responses to growth hormone stimulation. Growth hormone levels were measured in plasma samples obtained every 20 minutes for either 12 or 24 hours. The results were compared with those in 46 normal prepubertal children. Children with growth hormone deficiency had significantly lower mean 24-hour growth hormone levels (1.0 microgram per liter; range, 0.5 to 1.8) than normal children (2.8 micrograms per liter; range, 0.8 to 5.8; P less than 0.001). However, the diagnostic usefulness of the spontaneous growth hormone test was inferior to that of the stimulation tests, since it identified only 57 percent of the children with growth hormone deficiency identified by the stimulation tests. In the remaining children with growth hormone deficiency, spontaneous growth hormone levels were within the normal range. Children with idiopathic short stature had a normal mean 24-hour level of growth hormone (3.0 micrograms per liter; range, 1.1 to 6.7). No child in this group had low levels of spontaneous growth hormone secretion. We conclude that the measurement of the spontaneous secretion of growth hormone in prepubertal short children had lower sensitivity and offered no diagnostic advantage over stimulation tests. Our data do not support the routine measurement of spontaneous growth hormone secretion in the diagnosis of growth hormone deficiency.

Treatment of short stature and delayed adolescence

The treatment of growth failure in children with documented GH deficiency remains the only noncontroversial indication for GH therapy. There are increasing data suggesting that GH may be useful in treating some children with Turner's syndrome and with NVSS. Further studies, however, are necessary to evaluate the long-term efficacy and safety of GH therapy in these children. The treatment of non-GH deficient children whose heights are within two standard deviations of the mean height for age is clearly inappropriate and should be avoided, despite parental protests.

Growth and growth factors in diabetes mellitus

Growth of 79 children with diabetes was analysed at diagnosis and again after one to 10.7 years of treatment with insulin. Both sexes were tall at onset, whereas at the last observation boys alone showed significant growth retardation. Height standard deviation score (SDS), however, showed no significant fall either in 32 subjects reassessed after five years of disease or in 18 subjects examined at full stature. Skeletal maturity was not significantly impaired after treatment. Pubertal growth spurt was reduced, especially in girls and in subjects with onset of disease at or around puberty. We found no significant correlation between height and height velocity SDS and glycosylated haemoglobin values or secretion of growth hormone during the arginine test. Somatomedin C values were correlated with height velocity SDS in prepubertal boys. The results of this study suggest that there are interferences in the growth of children with diabetes but that they do not seem to have a significant influence on adult height.

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.

Growth hormone therapy of short stature

Considerable progress has been made in the diagnosis and treatment of growth hormone-related short stature. Knowledge about growth hormone releasing factor (GRF) and somatomedin C has provided the possibility of distinguishing between hypothalamic and pituitary growth hormone deficiency and growth hormone resistance. It has been shown that treatment with GRF may stimulate growth in certain cases of growth hormone deficiency. Recombinant DNA techniques may, in the near future, provide sufficient amounts of GRF, growth hormone and possibly somatomedin C for clinical use. At present, many countries have prohibited the use of human pituitary growth hormone due to a possible risk of transmission of Creutzfeldt-Jakob disease. It has become increasingly clear that several short children without classical growth hormone deficiency, may increase their growth velocity during growth hormone treatment. There are many medical, psychological, ethical and economical implications involved in the extended treatment of children with short stature. It is necessary to maintain a restricted approach towards the treatment of children with short stature, and such treatment should be prescribed and controlled by a limited number of well-trained paediatric endocrinologists. This article reviews some of the present knowledge in this rapid developing field of paediatric endocrinology.