Selective impairment of growth hormone response to physiological stimuli

Constitutional delay of growth and adolescence

Constitutional delay of growth and adolescence (CDGA) is characterized by simultaneous retardation of growth, skeletal maturation and sexual development. Primarily longitudinal growth is impaired. The late occurrence of puberty is a secondary phenomenon brought about by the retarded physical development. Plasma levels of sex hormones and gonadotrophin correlate with bone age, not with chronological age. The provocation tests for growth hormone (GH) show normal results. In contrast, the spontaneous secretion of GH, measured half-hourly through the night or over 24 hours, is markedly reduced. Plasma somatomedin C is diminished. According to these data, CDGA is not a genuine GH deficiency but represents a cybernetic disorder coinciding with a false threshold for GH. As shown by large series of investigations, the final height of the patients lies on average 1.85 SD below the mean of healthy adults, with large individual variations. The decision as to whether treatment by growth promoting hormones should be performed should be made with regard to the individual height prognosis. With GH in physiological doses growth velocity can be considerably increased. Bigger doses of the hormone appear to be necessary in order to enhance final height. Treatment by anabolics and testosterone increases height velocity only, not adult height.

Growth hormone therapy for short stature: panacea or Pandora's box?

Increased availability of growth hormone (GH) because of increased production using recombinant DNA technology has led to increased demand. Many children who do not have classic GH deficiency may respond to GH therapy. These observations require rethinking of the medical indications for GH therapy, and raise two central ethical questions: (1) Is it justified to discriminate on the basis of GH deficiency? (2) Whatever the indication for GH treatment, at what height should GH therapy be considered an entitlement? We argue, first, that GH responsiveness, not GH deficiency, should be the criterion for GH treatment, and that prior arguments emphasizing GH deficiency are based on vague or faulty notions of disease, handicap, or potential. Second, we argue that children who are handicapped (arbitrarily defined as including those whose height is below the 1st percentile) and GH responsive are entitled to treatment. Children above that height, whether GH deficient or not, may permissibly be treated, but there is no societal obligation to do so. Such an approach would reduce, though not eliminate, some of the more severe burdens of short stature without aggravating the pernicious effects of "heightism" in American society.

Twelve-hour spontaneous nocturnal growth hormone secretion in growth retarded patients

Twelve-hour nocturnal GH secretion was studied in 30 children with familial short stature (FSS), constitutional growth delay (CGD), total growth hormone deficiency (TGHD), partial growth hormone deficiency (PGHD), or idiopathic short stature (ISS). No difference was observed between subjects with FSS and children with CGD. The mean 12-hour serum GH concentration was significantly lower in patients with TGHD (p less than 0.001), children with PGHD (p less than 0.01), and subjects with ISS (p less than 0.01) than in subjects with FSS and CGD. No overlap was observed between the range of mean concentration values of children with TGHD and that of subjects with FSS. A significant correlation was found between growth velocity expressed as SD from the mean for bone age and GH concentration (p less than 0.001). All patients with a growth velocity less than 3rd percentile for bone age showed a mean nocturnal concentration less than 4 ng/ml. These data suggest that evaluation of 12-hour spontaneous nocturnal GH secretion with GH sampling every 30 minutes can be usefully employed in the diagnosis of GH deficiency.

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.

Comparison between a physiological and a pharmacological stimulus of growth hormone secretion: response to stage IV sleep and insulin-induced hypoglycaemia

Peak growth hormone (GH) response to insulin-induced hypoglycaemia was compared with peak GH concentration during the first cycle of stage IV sleep in 75 children. 65 children had concordant results: in 38 GH concentrations were greater than 15 mU/l and in 27 less than this value. Results were discordant in 10 children. Results of sleep sampling under electroencephalographic control of the assessment of GH secretion are comparable to conventional pharmacological studies in terms of efficiency, sensitivity, and percentage false-negatives. Sleep sampling has the advantage of being a physiological test of secretion.

Growth-hormone releasing factor and clonidine in children with constitutional growth delay. Evidence for defective pituitary growth hormone reserve

Six male prepubertal children with constitutional growth delay (CGD), and a subnormal growth hormone (GH) response to insulin hypoglycemia, and four normal prepubertal children were given in different occasions 1 microgram/Kg iv synthetic hpGRF-40 or a single oral dose of 0.15 mg/m2 clonidine (Clon), an effective growth hormone (GH) secretagogue. In the normal children brisk and clear-cut GH rises were detected in plasma after hpGRF-40 (peak GH levels at 15-30 min) or clonidine (peak GH levels 60-90 min). In CGD children hpGRF-40 induced a biphasic response, e.g. a slight increase in plasma GH at 15 min followed by a delayed and erratic GH rise occurring 45-120 min post-injection. Also the GH response to Clon was sluggish and delayed and peak plasma GH levels were attained only 90-180 min post-drug administration. These data indicate that the CGD children of our study have a defect in the pituitary GH reserve.

Evaluation of growth hormone release and human growth hormone treatment in children with cranial irradiation-associated short stature

We studied nine children who had received cranial irradiation for various malignancies and subsequently experienced decreased growth velocity. Their response to standard growth hormone stimulation and release tests were compared with that in seven children with classic GH deficiency and in 24 short normal control subjects. With arginine and L-dopa stimulation, six of nine patients who received radiation had a normal GH response (greater than 7 ng/ml), whereas by design none of the GH deficient and all of the normal children had a positive response. Only two of nine patients had a normal response to insulin hypoglycemia, with no significant differences in the mean maximal response of the radiation and the GH-deficient groups. Pulsatile secretion was not significantly different in the radiation and GH-deficient groups, but was different in the radiation and normal groups. All subjects in the GH-deficient and radiation groups were given human growth hormone for 1 year. Growth velocity increased in all, with no significant difference in the response of the two groups when comparing the z scores for growth velocity of each subject's bone age. We recommend a 6-month trial of hGH in children who have had cranial radiation and are in prolonged remission with a decreased growth velocity, as there is no completely reliable combination of GH stimulation or release tests to determine their response.

Sleep-induced growth hormone release--evaluation of a simple test for clinical use

Plasma growth hormone (GH) levels were measured during the first 2 hours of sleep without electroencephalogram monitoring and then after arginine infusion in 28 children investigated for short stature. Ten children considered GH deficient on clinical and biochemical grounds had concordantly low GH levels during sleep and after arginine stimulation. Of the 18 children without GH deficiency, 17 had GH levels greater than or equal to 15 mU/l during the sleep test (mean peak 39 mU/l) and 13 had GH levels greater than or equal to 15 mU/l after arginine infusion (mean peak 25 mU/l). A sleep test is safe, reliable, and practicable for routine clinical use.

Diagnosis and treatment of children with growth hormone deficiency

Growth hormone deficiency embraces a heterogeneous group of disorders with multiple aetiologies. The biggest single division is between those children whose growth hormone deficiency is due to a structural lesion and those where it is not. In both cases other pituitary hormones may, or may not, be affected, although when a structural lesion is present multiple pituitary hormone deficiency is the rule rather than the exception. In the absence of structural lesions the pathogenesis of the condition in still largely obscure, although some mechanisms, such as cranial irradiation, are now well recognized. Birth trauma is also now a strong candidate as a predisposing factor. The prevalence of growth hormone deficiency is still uncertain, but is probably about 1 in 4000 live births. The clinical features of growth hormone deficiency are usually fairly clear, with short stature, low growth velocity, excess subcutaneous fat and delayed skeletal maturation being the principal clinical features. Laboratory investigation still largely depends upon the assessment of pituitary growth hormone secretion in response to a variety of provocation tests and is still in many ways unsatisfactory. Treatment consists of parenteral growth hormone replacement using material of human cadaveric origin. Non-primate growth hormones are of no value. Other endocrine abnormalities, when present, are treated appropriately, and with early diagnosis and optimal therapy the height prognosis is reasonably good. The principal aims for the future must be to ensure supplies of therapeutic growth hormone, improve some of the diagnostic procedures and ensure early ascertainment.

Growth and somatomedin-C responses to growth hormone in dwarfed children

Nineteen children were studied because of short stature. They had in common abnormally low Sm-C values for age, and each received a ten-day course of exogenous GH therapy. Based on their endogenous GH concentrations and the response to GH therapy, in terms of Sm-C and height increments, they were classified into three groups. Group I included patients with GH insufficiency who had blunted GH responses to stimulation, but responded to therapy by normalizing the Sm-C concentration and velocity of growth. Group II patients all had normal GH responses to stimulation, but their responses to exogenous GH were similar to those observed in the GH deficient subjects. In the two children in Group III who had normal release of endogenous GH, Sm-C values and growth rate did not increase in response to GH. Group II patients may represent children with biologically inactive but immunoreactive GH, whereas the children in Group III are examples of the Laron type of dwarfism. Thus, rather than the plasma GH response to provocative stimuli, the Sm-C and growth increment responses to short-term exogenous GH therapy may more precisely identify children that will benefit from long-term GH therapy.

Growth hormone release during sleep in growth-retarded children with normal response to pharmacological tests

Twenty-one prepubertal children of small stature, 10 boys and 11 girls, aged from 4-3 to 12-8 years, were studied. Their height was less than 3rd centile, and during the preceding year all had a growth rate less than 4-5 cm/year. Arginine and L-dopa tests were given, and the release of growth hormone (GH) during monitored sleep was investigated. On the basis of the electroencephalogram and horizontal electro-oculogram, sleep was divided into stages 1-2-3-4 and rapid-eye-movement. All the children had a GH response greater than 8 ng/ml in at least one of the two pharmacological tests, and were therefore accepted as not suffering from GH deficiency. In all 21 children during sleep there was at least one secretory peak with GH greater than 8 ng/ml. Of a total of 46 secretory peaks recorded, 22 (48%) took place during deep, slow sleep (stages 3-4), 10 (22%) during light sleep (stage 2), 10 (22%) during REM sleep, and 4 (8%) during wakening. In 4 patients (19%) no secretory peak was observed during stages 3-4, even though there were peaks at other times. The data (a) show that it is essential to monitor GH throughout the night to ascertain with certainty the presence or absence of physiological secretory peaks of GH; (b) emphasise the rare disagreement between pharmacological and physiological tests; (c) suggest the use of this physiological test for GH secretion in those cases where the insulin test may be hazardous.

Prevalence of severe growth hormone deficiency

Four hundred and forty-nine short children, who were all over 2-5 standard deviations below the mean height for age, were identified by screening the heights of 48 221 6- to 9-year-old children in three Scottish cities. Most were screened for growth hormone deficiency (GHD). The prevalence of severe GHD in this sample may have been as high as 1 in 4018, much higher than reported. The findings suggest that present referral patterns may account for the delayed or missed diagnosis of the condition in girls or children with less severe short stature.

Nyctohemeral secretion of growth hormone in normal children of short stature and in children with hypopituitarism and intrauterine growth retardation

A continuous blood sampling technique has been used to monitor human growth hormone (GH) during sleep in fourteen normal short children (age range 6.5-15.0 years), twelve hypopituitary children (2.8-17.3 years), three children with psychosocial GH deficiency (4.0-13.0 years), and three children with intrauterine growth retardation (9.5-11.3 years). The mean GH level of a 5 h sleep period (22.30-03.30 hours) was used to represent the GH response to sleep. The GH response to insulin induced hypoglycaemia (IST) was also determined. In normal short children there was a significant relationship between 5 h mean GH levels and chronological age. The curve defining this relationship was similar to the third centile linear growth velocity curve. The 5 h mean GH levels of the hypopituitary and psychosocial GH deficiency children were more than 2 SD below the age related mean established for normal short children. The children with intrauterine growth retardation demonstrated values which were more than 2 SD above the age related mean.