Growth hormone release during sleep in growth retarded children

Acute Sleep Disruption Does Not Diminish Pulsatile Growth Hormone Secretion in Pubertal Children

Context

In children, growth hormone (GH) pulses occur after sleep onset in association with slow-wave sleep (SWS). There have been no studies in children to quantify the effect of disrupted sleep on GH secretion.

Objective

This study aimed to investigate the effect of acute sleep disruption on GH secretion in pubertal children.

Methods

Fourteen healthy individuals (aged 11.3-14.1 years) were randomly assigned to 2 overnight polysomnographic studies, 1 with and 1 without SWS disruption via auditory stimuli, with frequent blood sampling to measure GH.

Results

Auditory stimuli delivered during the disrupted sleep night caused a 40.0 ± 7.8% decrease in SWS. On SWS-disrupted sleep nights, the rate of GH pulses during N2 sleep was significantly lower than during SWS (IRR = 0.56; 95% CI, 0.32-0.97). There were no differences in GH pulse rates during the various sleep stages or wakefulness in disrupted compared with undisrupted sleep nights. SWS disruption had no effect on GH pulse amplitude and frequency or basal GH secretion.

Conclusion

In pubertal children, GH pulses were temporally associated with episodes of SWS. Acute disruption of sleep via auditory tones during SWS did not alter GH secretion. These results indicate that SWS may not be a direct stimulus of GH secretion.

Sleep and Puberty

In the 1970's, Boyar and colleagues made the seminal observation that during the early stages of puberty, there is a sleep-specific augmentation of pulsatile luteinizing hormone (LH) secretion. Building on this tantalizing association between sleep and the re-awakening of the neuro-reproductive axis, a number of investigators have since mapped the dynamic relationship between sleep and reproductive hormones across the pubertal transition. In this review, we focus on the complex, reciprocal relationship between sleep and reproductive hormones during adolescence as well as the potential effects of melatonin and orexin on gonadotropin-releasing hormone (GnRH) activity in children with chronic insomnia and narcolepsy, respectively. Given the important interaction between the reproductive and somatotropic axes during puberty, we end with a discussion of sleep and growth hormone (GH) secretion in children.

Characterizing pediatric inpatient sleep duration and disruptions

OBJECTIVE

To contextualize inpatient sleep duration and disruptions in a general pediatric hospital ward by comparing in-hospital and at-home sleep durations to recommended guidelines and to objectively measure nighttime room entries.

METHODS

Caregivers of patients four weeks - 18 years of age reported patient sleep duration and disruptions in anonymous surveys. Average at-home and in-hospital sleep durations were compared to National Sleep Foundation recommendations. Objective nighttime traffic was evaluated as the average number of room entries between 11:00pm and 7:00am using GOJO brand hand-hygiene room entry data.

RESULTS

Among 246 patients, patients slept less in the hospital than at home with newborn and infant cohorts experiencing 7- and 4-h sleep deficits respectively (Newborn: 787 ± 318 min at home vs. 354 ± 211 min in hospital, p < 0.001; Infants: 703 ± 203 min at home vs. 412 ± 152 min in hospital, p < 0.01). Newborn children also experienced >2 h sleep deficits at home when compared to NSF recommendations (Newborns: 787 ± 318 min at home vs. 930 min recommended, p < 0.05). Objective nighttime traffic measures revealed that hospitalized children experienced 7.3 room entries/night (7.3 ± 0.25 entries). Nighttime traffic was significantly correlated with caregiver-reported nighttime awakenings (Spearman Rank Correlation Coefficient: 0.83, p < 0.001).

CONCLUSION

Hospitalization is a missed opportunity to improve sleep both in the hospital and at home.

Auxological and biochemical assessment of short stature

Measurements of height and calculation of height velocity are highly accurate and sensitive to changes in a child's health. Definition of normality must be based on height velocity, and it is not acceptable to label a child as short and normal purely on the basis of a biochemical test unless this is substantiated with the demonstration of a normal height velocity. Response to therapy is dependent on the child's pretreatment growth rate and also on the amount of GH administered and the frequency of administration.

Neuroendocrine control of growth hormone secretion

The secretion of growth hormone (GH) is regulated through a complex neuroendocrine control system, especially by the functional interplay of two hypothalamic hypophysiotropic hormones, GH-releasing hormone (GHRH) and somatostatin (SS), exerting stimulatory and inhibitory influences, respectively, on the somatotrope. The two hypothalamic neurohormones are subject to modulation by a host of neurotransmitters, especially the noradrenergic and cholinergic ones and other hypothalamic neuropeptides, and are the final mediators of metabolic, endocrine, neural, and immune influences for the secretion of GH. Since the identification of the GHRH peptide, recombinant DNA procedures have been used to characterize the corresponding cDNA and to clone GHRH receptor isoforms in rodent and human pituitaries. Parallel to research into the effects of SS and its analogs on endocrine and exocrine secretions, investigations into their mechanism of action have led to the discovery of five separate SS receptor genes encoding a family of G protein-coupled SS receptors, which are widely expressed in the pituitary, brain, and the periphery, and to the synthesis of analogs with subtype specificity. Better understanding of the function of GHRH, SS, and their receptors and, hence, of neural regulation of GH secretion in health and disease has been achieved with the discovery of a new class of fairly specific, orally active, small peptides and their congeners, the GH-releasing peptides, acting on specific, ubiquitous seven-transmembrane domain receptors, whose natural ligands are not yet known.

[Evaluation of dietary vitamin A intake in children with and without growth retardation]

BACKGROUND

A possible involvement of vitamin A in regulating physiological nocturnal growth hormone secretion has been recently suggested leading us to evaluate the daily vitamin A supply in prepubertal school children.

POPULATION AND METHODS

A questionnaire including a list of foods containing vitamin A and/or beta-carotene was answered with the aid of the parents. Vitamin A supply was expressed in retinol-Equivalent and estimated as mean daily intake over a one-year period. Following this methodology, a study was conducted in 104 control school children with normal stature and 110 children with short stature.

RESULTS

The total daily vitamin A intake (mean +/- SD: 1.197 micrograms +/- 799), retinol (675 micrograms +/- 628) and beta carotene (525 micrograms +/- 355) was above or equal to the recommended intake in more than 75% of the control children. In contrast, the total daily vitamin A intake (mean +/- SD: 787 micrograms +/- 850, P < 0.0002) retinol (436 micrograms +/- 670, P < 0.0004) and beta carotene (353 micrograms +/- 466, P < 0.002) was significantly decreased in those children with short stature, more than 35% of them having daily intake below the recommended one. The dietary vitamin A intake was also deficient when expressed as ER/1,000 calories (mean SD = 444 +/- 262) in the 46 children with short stature in whom the calorie intake had been evaluated for three days.

CONCLUSIONS

This study confirms that annual dietary vitamin A intake can easily be measured in school children. Its results suggest that this intake, relatively deficient in children with short stature, could be correlated with deficient secretion of growth-hormone.

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.

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.

The relationship between height velocity and growth hormone secretion in short prepubertal children

We have performed 24 h growth hormone (GH) profiles in 50 short prepubertal children aged between 5.2 and 12.9 years, growing with height velocity standard deviation scores (SDS) between 0.4 and -3.9. There was an asymptotic relationship between height velocity and spontaneous GH secretion described by the equation: height velocity SDS = A-B(e-cx), where A, B and C are constants and x is a measure of spontaneous GH secretion. We considered GH pulse amplitude to be the better description of spontaneous GH secretion as duration of the GH pulse (the time component of area under the curve) contributed little to the relationship between height velocity and area under the pulse. The distribution of GH secretion was continuous and there was no dividing point between GH insufficiency and sufficiency. Similar overlap was observed when the results of GH responses to insulin induced hypoglycaemia were considered; 14% of slowly growing children (height velocity SDS less than -0.8), had a response greater than 15 mU/l. Likewise serum IGF-I concentrations could not clearly separate slowly growing children from normal individuals. We conclude that height velocity, which ultimately determines height achieved, is controlled predominantly by GH pulse amplitude. The findings suggest that short normal children growing along or parallel to the third height centile could be made to grow faster by the administration of exogenous GH.

Physiological growth hormone secretion during slow-wave sleep in short prepubertal children

The usefulness of a limited nocturnal GH profile has been evaluated for the assessment of physiological GH secretion. We have analysed the complete overnight GH and sleep profiles of 20 short prepubertal children, sampled at 15-min intervals. The mean age was 9.1 years (range 4.3-11.7 years) and mean height velocity standard deviation score (SDS)-1.0 (range -2.4 to +0.4). The sleep stage in which the maximal GH value was reached varied considerably between the patients. Only 55% achieved the maximal GH value during the first slow-wave sleep period, and 65% in the first 2 h of sleep. The maximal values during the first slow-wave period correlated weakly with the sum of the nocturnal peak values and the total area under the curve of the complete GH profile. None of these parameters correlated with height velocity. We conclude that at present there is no substitute for complete overnight or 24 h GH profiles for the assessment of physiological GH secretion, but the clinical significance of the variations seen remains unclear.

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.

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.

Use of growth hormone-gel

We evaluated the efficacy of a depot preparation of growth hormone (GH) in a 15% gelatin solution (GH-gel) in the treatment of 15 growth hormone-deficient children. The studies were designed to see if prolonging absorption of GH to achieve lower more physiological concentrations of GH in plasma would decrease the frequency of injection, reduce the amount of GH needed for effective therapeutic response, and improve the response to long-term treatment. We found that after a single dose of GH-gel the plasma concentrations of GH were lower than those achieved after the standard aqueous preparation. The preparation was efficacious in promoting growth and our 1st study of 6 patients suggested that GH-gel given twice a week had a growth response equal to that of the three-times a week aqueous schedule. However both schedules resulted in the frequently observed decreased growth rate during the second treatment year. Our 2nd study, attempting to ameliorate this waning effect by using the GH-gel preparation twice a week in a weight-adjusted dose during the entire second year did not resolve the problem. Thus, GH in depot gel results in more physiological plasma concentrations of GH and may be beneficial in reducing the quantity of hormone needed and the injection frequency but it does not offer a solution to the waning response to the long-term administration of GH.

Multiple pituitary hormone deficiencies in eight siblings of one Jewish Moroccan family

In a Jewish Moroccan inbred family, 8 of 12 siblings were found to have multiple deficiencies of pituitary hormones, including GH, TSH and gonadotrophins. The parents showed no deficiency and are in good health, as are the other 4 siblings. The investigations carried out indicate that in this family the etiology is hereditary in nature, probably being autosomal recessive, with the defect located in the pituitary gland.

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.

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.

X-linked mental retardation associated with macro-orchidism

Two families are described with an X-linked form of mental retardation in whom the affected males were found to have bilateral enlargement of the testes. No conclusive evidence of any endocrinological disturbance was found.

Selective impairment of growth hormone response to physiological stimuli

In a consecutive group of 25 children with defective growth being evaluated for growth hormone deficiency, EEG-monitored slow-wave sleep provided discriminatory serum growth hormone responses equivalent to those obtained by arginine and insulin-hypoglycaemia provocation. Exercise was less effective but was able to provide a useful screening test. In 2 subjects with abnormal physiological but normal pharmacological serum growth hormone responses, therapeutic administration of growth hormone in one resulted in a significant growth increment, whereas in the other, advanced epiphyseal maturity precluded adequate evaluation. A normal growth hormone response to a pharmacological stimulus does not exclude a therapeutic response to human growth hormone.

Fenfluramine and growth hormone release

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