Growth hormone secretory patterns in children with short stature

To assess whether growth-retarded children with a stimulated growth hormone (GH) level greater than 10 ng/mL have an abnormality in spontaneous GH secretion, we measured GH levels every half hour for 24 hours in 50 children 2.7 to 17 years of age. Growth rate was subnormal in all. Mean 24-hour GH concentration ranged from 1.2 to 7.7 ng/mL, and was significantly greater in pubertal than in prepubertal children (P less than 0.01). In both groups, GH concentration during sleep was significantly greater than during wakeful hours (P less than 0.0005); 24-hour GH concentration correlated significantly with sleep-induced GH peak. A decrease in 24-hour GH concentration and sleep-induced GH peak were noted in four pubertal children with stimulated GH less than 15 ng/mL. A progressive and significant increase in somatomedin C (SmC) level was noted with increasing age and sexual development. No correlations were found between 24-hour GH concentration and rate of growth, age, or bone age. Serum SmC values correlated significantly with age and bone age (P less than 0.01), and with 24-hour GH concentration only in prepubertal children (P less than 0.05). A strong correlation between SmC and growth rate was noted only in pubertal children (P less than 0.01). Growth velocity increased significantly during GH therapy regardless of the 24-hour GH concentration. Our results indicate that in children with growth retardation there is a wide variation in 24-hour GH concentration and a significant increase in GH concentration during puberty; the GH concentration during nocturnal sleep, rather than an entire 24-hour GH concentration, can be used for evaluation; during puberty the SmC level reflects sexual development more than GH reserve; and GH therapy appears to increase growth velocity in both non-GH-deficient and partially GH-deficient short children.     

Growth hormone secretory dynamics in children with precocious puberty

We investigated whether an increase in growth hormone secretion contributed to the growth spurt in children with precocious puberty by measuring the 24-hour profile of serum growth hormone in 51 patients with central precocious puberty. Girls with central precocious puberty had significantly greater mean 24-hour levels of growth hormone in comparison with normal prepubertal girls (5.1 +/- 0.5 SEM vs 3.4 +/- 0.3 ng/mL, P less than 0.005). Mean 24-hour growth hormone levels did not differ significantly between boys with central precocious puberty and normal prepubertal boys (4.4 +/- 1.2 vs 3.0 +/- 0.4 ng/mL). Serum somatomedin C levels were significantly correlated with mean 24-hour growth hormone levels in the girls only. Height age advancement (expressed as height age/chronologic age) was significantly correlated with mean 24-hour growth hormone levels in both boys and girls with central precocious puberty. We conclude that spontaneous 24-hour growth hormone secretion in girls with precocious puberty is greater than that of normal prepubertal girls and may mediate at least in part the increased growth rate in this disorder.     

Growth hormone secretory dynamics in Turner syndrome

We investigated whether a decrease in serum growth hormone contributes to the short stature of adults with Turner syndrome by measuring the 24-hour profile of serum growth hormone in 30 patients aged 2 to 20 years. Growth hormone pulses were defined as a rise from nadir to peak that exceeded three times the intraassay coefficient of variation. Girls with Turner syndrome aged 2 to 8 years did not have statistically different growth hormone levels, peak amplitudes, and peak frequencies compared with those in age-matched controls. By contrast, girls with Turner syndrome aged 9 to 20 years had significantly decreased mean 24-hour growth hormone levels, peak amplitudes, and peak frequencies compared with those in age-matched normal girls. Patients with Turner syndrome of all ages had decreased serum somatomedin-C concentrations and delayed bone ages. We conclude that a relative deficiency of growth hormone in pubertal patients with Turner syndrome may contribute to their adult short stature.     

Growth hormone therapy in short stature

Unlimited availability of growth hormone (GH), and the demonstration of increased growth velocity (GV) during GH treatment in non-GH-deficient children have suggested new indications for GH therapy in short stature. There are two principle conditions with GH-related short stature: classical growth hormone deficiency (CGHD) and growth hormone neurosecretory dysfunction (GHND). Present knowledge about the effects of GH treatment in these and other disorders of short stature are reviewed. In non-CGHD, it is not possible to predict the short-term effect on growth during GH therapy, and even if GV increases, the effect on final adult height remains to be documented. This, together with potential side effects and the high expense of GH treatment, exhort to a restricted attitude towards routine GH treatment of short children without GH deficiency.     

Growth hormone-releasing hormone: studies in normal subjects and patients with disorders of growth hormone secretion

Growth hormone-releasing hormone (GHRH) has been characterised as a 40-44 residue peptide with full biological activity residing in the first 29 residues. In normal subjects GHRH selectively promotes the release of growth hormone (GH) with little change in responsiveness throughout childhood and young adult life. The majority of 'GH-deficient patients' show a GH response to GHRH, suggesting that they have a hypothalamic defect in GH release. GHRH given subcutaneously promotes growth in 50% of GH-deficient children, and it is likely that depot-preparations of GHRH will provide a practical alternative treatment for GH deficiency. GHRH has provided an important method to evaluate pituitary GH reserve and has greatly improved our understanding of both normal and abnormal GH secretion.     

Short stature with normal growth hormone and elevated IGF-I

We report on a Japanese girl with short stature, malar hypoplasia, up-slanting palpebral fissures, blue sclerae and thin, stiff and slightly brownish hair. Short stature started in utero and her psychomotor development was normal. Menarche appeared at 13 years 8 months. Height at 14 years 5 months was 132 cm (–4.6 SD). Her growth hormone (GH) sleep pattern and responses to insulin,l-dopa, arginine, propranolol-glucagon and growth hormone-releasing hormone were normal. Plasma insulin-like growth factor I (IGF-I) was high (2170–4860 units/l) and increased from 4860 to 7080 units/l 20 h after biosynthetic GH injection. Gel infiltration patterns of the free and protein-bound IGF-I in plasma from the patient were not different from the controls; IGF-I fraction of the high and low molecular weight binding protein and the non-protein bound fraction were 75.5%, 15.8% and 8.7%, respectively. IGF-I from the patient showed normal bioactivities when determined by [³⁵S]sulphate and [³H]thymidine uptake into cultured rat chondrocytes, and by [³H]thymidine and [³H]-aminoisobutyric acid uptake into the patient's skin fibroblasts. IGF-I binding to cultured skin fibroblasts from the patient was comparable to that of controls. These results suggest that tissue specific defects of IGF-I receptors may be the cause of increased IGF-I levels in the patient.     

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.     

Growth hormone secretion in children and adolescents with familial tall stature

Sixty-five patients (22 boys and 43 girls) presenting with familial tall stature were investigated with regard to growth hormone (GH) secretion, both physiological and after stimulation with thyrotropin releasing hormone (TRH) and growth hormone relasing hormone (GHRH). Plasma insulin-like growth factor-I (IGF-I) was also measured. Two groups of patients were distinguished according to their physiological secretion of GH: a high secretory group (n=49) with a mean 24 h integrated concentration of GH (IC-GH) of 5.4±2.3 g/l per minute and a large number of peaks (5.1±1.6 in 24 h), and a low secretory group (n=16) with a mean 24 h IC-GH of 2.1±0.5 g/l per minute and few peaks (3.3±1.3 in 24h). Plasma IGF-I levels and GH peak values after the TRH test were significantly higher in the high secretory group. These results indicate that familial tall stature is the consequence either of hypersecretion of GH or of hypersensivity to this hormone (IGF-I levels being normal in spite of low GH levels).     

Long-term treatment with growth hormone of children with short stature and normal growth hormone secretion.

Children with short stature but normal growth rate and/or normal growth hormone response to sleep and secretagogues were treated with recombinant methionyl human growth hormone, 0.3 mg/kg per week. In each year of treatment, about 80% of the subjects maintained an increase in growth rate greater than the defined limit (greater than 1 cm/yr above pretreatment growth rate) for continuation of human growth hormone treatment. Comparison of the group that continued to respond to human growth hormone with the group that did not maintain an accelerated growth rate did not reveal differences in bone age delay, sleep or secretagogue-stimulated human growth hormone secretion, degree of short stature either absolute or relative to target height, and somatomedin C concentration before or after initiation of therapy. The group that failed to respond to the human growth hormone treatment in the first year of treatment was younger and had a higher pretreatment growth rate. Review of the longitudinal growth curves revealed five patterns of response to human growth hormone treatment: (1) failure to increase growth rate in two subjects with height SD scores within 1 SD of target height, (2) failure to increase growth rate in five subjects with height SD scores greater than 1 SD less than the target height, (3) acceleration in growth rate in three subjects that was not maintained until achievement of a height within 1 SD of the target height, (4) acceleration of growth rate in five subjects that was maintained until achievement of a height within 1 SD of the target height, and (5) acceleration in growth rate that was maintained during the 3 years of treatment in 15 subjects who had not attained a height within 1 SD of the target height. We conclude that human growth hormone treatment of some but not all short children with "normal" growth hormone secretion will result in sustained acceleration of growth rate and attainment of prepubertal heights that are closer to but do not exceed their genetic height potential. A clinical trial of human growth hormone may be necessary to determine which subjects will benefit from the treatment.     

Growth hormone therapy for short stature in Diamond Blackfan anemia

BACKGROUND: We report a 13-year-old male with Diamond Blackfan anemia and short stature. He had a normal biochemical response to growth hormone (GH) stimulation, but his bone age was delayed, his insulin-like growth factor 1 (IGF-1) was low, and he had a poor growth velocity. He was started on daily GH injections. METHODS: From the patient's medical record the following data were collected: serial heights, serial weights, hemoglobin, hematocrit, bone age, IGF-1, and steroid dose. RESULTS: This patient had an increase in growth velocity up to 8.2 cm/year. CONCLUSIONS: Growth hormone therapy should be considered in children with DBA, short stature and poor growth velocity.     

Growth hormone for short stature not due to classic growth hormone deficiency

The advent of recombinant DNA technology has resulted in potentially unlimited supplies of growth hormone. Sufficient quantities are now available not only for the long-term, uninterrupted treatment of GH-deficient children but potentially for the treatment of non-GH-deficient patients with other short stature or growth attenuating disorders. Short-term studies have demonstrated an improvement in the growth rates of subjects with isolated short stature, Turner syndrome, and chronic renal failure; and additional studies are under way to assess the efficacy of GH therapy of other short stature syndromes. However, the long-term efficacy and possible adverse effects of GH treatment in these situations is not known. Until there has been more experience, GH deficiency should remain the primary indication for GH treatment. Growth hormone should not be considered routine therapy for other conditions associated with or resulting in short stature. However, research should continue in these areas to define which children may benefit from GH treatment.     

Growth hormone secretory pattern in non-obese children and adolescents with Prader-Willi syndrome

The aetiology of impaired growth hormone (GH) secretion in Prader-Willi syndrome (PWS) remains controversial due to the common occurrence of obesity. To further clarify whether suboptimal GH secretion in PWS is an artefact of excess weight, we evaluated both GH immunological activity and GH bioactivity after arginine administration in 23 non-obese PWS patients [seven females, aged 6.9 +/- 0.9 years, body mass index (BMI) SDS 0.63 +/- 0.26], in comparison with a control group of 32 healthy subjects, matched for age, gender and BMI (10 females, aged 7.9 +/- 0.3 years, BMI SDS 0.21 +/- 0.20). Serum GH concentration was measured with a time-resolved immunofluorometric assay (IFMA), while GH bioactivity was evaluated by the Nb2 cell bioassay. Serum IGF-I concentrations were measured by double-antibody RIA. GH mean peak after pharmacological stimulation was significantly lower in PWS individuals compared with controls when measured either by IFMA (6.05 +/- 1.23 microg/L vs. 23.7 +/- 1.06 microg/L, p < 0.0001) or by Nb2 (6.87 +/- 0.55 microg/L vs. 12.88 +/- 0.19 microg/L, p < 0.0001). Analysis of integrated GH secretion (AUC) confirmed that the PWS group differed significantly from the control subjects (387.9 +/- 76.1 microg/L/h vs. 1498.1 +/- 56.2 microg/L/h, p < 0.0001); the same result was obtained when the GH rise after arginine administration was expressed as nAUC (278.2 +/- 53.3 microg/L/h vs. 1443.6 +/- 52.5 microg/L/h, p < 0.0001). PWS patients had an IGF-I SDS significantly lower than those found in control subjects (p < 0.0001). Subnormal IGF-I values were present in 19 PWS individuals (82.6%) and two healthy controls (6.2%). These findings are in agreement with the hypothesis that a complex derangement of hypothalamus-pituitary axis occurs in PWS.     

Short stature associated with normal growth hormone and decreased somatomedin-C concentrations: response to exogenous growth hormone

Two prepubertal males with low somatomedin-C concentrations in their sera, but normal growth hormone concentrations, had positive metabolic responses when human growth hormone was administered. An accelerated velocity of growth accompanied the long-term administration of growth hormone. This response was dependent upon the administration of exogenous hormone inasmuch as linear growth was subnormal both before and after administration of growth hormone. The extreme short stature in these individuals may be secondary to a biologically inactive growth hormone molecule that is immunologically reactive or to a decreased dose responsiveness of the cells that produce somatomedin when exposed to the usual concentrations of endogenous growth hormone.     

Growth hormone secretion following administration of growth hormone releasing hormone in constitutional short stature and idiopathic growth hormone deficiency

A stimulation test using 1 microgram growth-hormone-releasing factor (GRF 1-29 X NH2)/kg bodyweight was performed in children with familial short stature and in children with constitutional delay of growth and development. The GH secretion induced by this means was not different in these groups, but there was a difference in the response between normal children and children with idiopathic growth hormone deficiency (GHD). GH secretion after GRF administration was significantly lower in the GHD group than in the other groups. However, 6 of 24 patients with GHD responded to the test with a normal increase in GH (greater than 10 ng/ml), and 11 with an intermediate response (2-10 ng/ml). Thus, the test does not differentiate individual patients with defective growth hormone secretion from normal short children.