Human growth hormone release during sleep: electroencephalographic correlation

Chrono-Endocrinology in Clinical Practice: A Journey from Pathophysiological to Therapeutic Aspects

This review was aimed at collecting the knowledge on the pathophysiological and clinical aspects of endocrine rhythms and their implications in clinical practice, derived from the published literature and from some personal experiences on this topic. We chose to review, according to the PRISMA guidelines, the results of original and observational studies, reviews, meta-analyses and case reports published up to March 2024. Thus, after summarizing the general aspects of biological rhythms, we will describe the characteristics of several endocrine rhythms and the consequences of their disruption, paying particular attention to the implications in clinical practice. Rhythmic endocrine secretions, like other physiological rhythms, are genetically determined and regulated by a central hypothalamic CLOCK located in the suprachiasmatic nucleus, which links the timing of the rhythms to independent clocks, in a hierarchical organization for the regulation of physiology and behavior. However, some environmental factors, such as daily cycles of light/darkness, sleep/wake, and timing of food intake, may influence the rhythm characteristics. Endocrine rhythms are involved in important physiological processes and their disruption may cause several disorders and also cancer. Thus, it is very important to prevent disruptions of endocrine rhythms and to restore a previously altered rhythm by an early corrective chronotherapy.

Chronotype and athletes’ performance in sports: A narrative review

The circadian system is managed by the suprachiasmatic nucleus, which is also called a master clock, and peripheral clocks spread all over the body. A complex system of neuronal, hormonal, and autonomous signals coordinates these clocks. However, this narrative review aimed to discuss the influence of circadian rhythms on the athlete’s performance, rate of perceived exertion, resynchronization, and aerobic and anaerobic exercise. An adequately timed wake-up is believed to play an essential role in an athlete’s performance. Based on the literature, chronotype appears to correlate with ratings of perceived exertion and fatigue scores, and morning types are less fatigued in the morning. When chronotype was evaluated, fatigue and vigor had time-by-group interactions. Swimmers with morning-type profiles showed lower fatigue scores before the (06:30 hour) time test than before the (18:30 hour) time test, while those with neither-type profiles had similar fatigue scores in both sessions. Vigor scores were also higher in the morning types than in the neither-types (17.9±7.1) before the morning test and (15.6±5.5) before the evening test. Studies have also shown that exercise enhances aerobic capacity based on the day. However, several reasons can lead to conflicting evidence regarding the chronotype effect on performance studies. Thus, more research is needed regarding the chronotype effect on athletes’ performance and the impact of time of day on muscle strength.

Important Hormones Regulating Lipid Metabolism

There is a wide variety of kinds of lipids, and complex structures which determine the diversity and complexity of their functions. With the basic characteristic of water insolubility, lipid molecules are independent of the genetic information composed by genes to proteins, which determine the particularity of lipids in the human body, with water as the basic environment and genes to proteins as the genetic system. In this review, we have summarized the current landscape on hormone regulation of lipid metabolism. After the well-studied PI3K-AKT pathway, insulin affects fat synthesis by controlling the activity and production of various transcription factors. New mechanisms of thyroid hormone regulation are discussed, receptor α and β may mediate different procedures, the effect of thyroid hormone on mitochondria provides a new insight for hormones regulating lipid metabolism. Physiological concentration of adrenaline induces the expression of extrapituitary prolactin in adipose tissue macrophages, which promotes fat weight loss. Manipulation of hormonal action has the potential to offer a new therapeutic horizon for the global burden of obesity and its associated complications such as morbidity and mortality.

The severity of obstructive sleep apnoea does not influence ambient IGF-I levels

OBJECTIVE

Obstructive sleep apnoea (OSA) is reported to have effects on a number of hormone systems including the hypothalamo-pituitary axis. We aimed to determine the impact of OSA severity on insulin-like growth factor-I (IGF-I) levels.

DESIGN AND METHODS

This is a prospective cohort study performed between November 2014 and May 2017. IGF-I was measured on serum samples, and data were collected on demographics, BMI and parameters of OSA.

RESULTS

611 participants were recruited (202 female, 53.5 ± 12.5 years; mean BMI 36.2 ± 8.0 kg/m² ). 26.2% had mild OSA; 27.3%, moderate OSA; and 44.5%, severe OSA. 15.2% of IGF-I values were below the age-related reference range. Increasing BMI correlated with greater AHI (r = .28, p < .001), ODI (r = .30, p < .001), severity of OSA (r = .17, p < .001), duration with oxygen saturation (SaO₂ ) <90% (r = .29, p = .001) and reduced median SaO₂ levels (r = .19, p < .001). IGF-I levels correlated negatively with age (r = -.13, p = .001), BMI (r = -.16, p < .001), diabetes (r = -.108, p = .009), AHI (r = -0.10, p = .043) and severity of OSA (r = -.10, p = .013). No association of IGF-I was observed with ODI, median SaO₂ levels or duration of SaO₂  < 90%. Regression analyses were used to examine determinants of IGF-I, all of which contained the independent variables of age, gender and BMI. All models showed IGF-I to be predicted by age and BMI (p < .05); however, none of the parameters of OSA were significant within these models.

CONCLUSION

Insulin-like growth factor-I levels in OSA are dependent on age and BMI; however, no additional effect of any OSA parameter was observed, supporting the hypothesis that OSA effects on IGF-I are indirect through concomitant body composition and metabolic parameters.

Endocrine rhythms and sport: it is time to take time into account

BACKGROUND

Studies of time-related biological phenomena have contributed to establishing a new scientific discipline, the chronobiology, which considers biological phenomena in relation to time. Sports activity profoundly affects the temporal organization of the organism and endocrine rhythms play a key role in the chronoorganization of individuals and are particularly important for correct physical activity. Correctly reading rhythmic hormonal variations of the human organism opens new horizons to sports medicine.

OBJECTIVE

This review is aimed at clarifying the relationship between endocrine rhythms and sports activities on the basis of the latest data in the literature.

METHOD

Data acquisition was obtained from three databases (PubMed, Scopus and SPORTDiscus), paying particular attention to reviews, meta-analysis, original and observational studies on this issue.

RESULTS

After the description of the general characteristics and parameters of biological rhythms, the main endocrine rhythms will be described, highlighting in particular the interrelationships with sports activity and focusing on the factors which can affect negatively their characteristics and consequently the psychophysical performances of the athletes.

CONCLUSION

Knowledge of this issue may allow establishing the best form of competitive or amateur activity, through the collaboration of an informed athlete and a sports physician attentive to biological rhythms. By taking into account that alteration of physiological rhythmic temporal organization can favour the onset of important diseases, including cancer, this will lead to the expected performances without impairing the correct chronoorganization of the athlete.

Molecular basis of growth hormone daily mRNA and protein synthesis in rats

AIMS

Daily and seasonal rhythms coordinate the endocrine and metabolic functions. The pituitary gland is the master regulator of several endocrine activities, and its function is classically regulated by endocrine signals from its target glands as well as from the hypothalamus. The growth hormone (GH) produced and secreted by the anterior pituitary presents a pulsatile secretion throughout the 24-hour cycle. However, the molecular mechanisms regulating the daily pattern of GH secretion are still unclear. Herein we investigated whether circadian GH mRNA and protein synthesis is modulated by acute adjustments in the stability and expression of GH mRNA.

MAIN METHODS

GH mRNA and protein content were evaluated by real-time PCR and Western blotting, respectively, in pituitary gland of rats euthanized every 3 h during a 24-h period at the Zeitgeber times (ZT3 to ZT24). The GH mRNA poly(A) tail length was determined by RACE-PAT assay.

KEY FINDINGS

We identified two main peaks of GH mRNA level in the pituitary gland of rats; one in the middle of the light-cycle and another in the middle of the dark-cycle. The latter was associated with an increase in pituitary GH protein content. Interestingly, an increment in the poly(A) tail length of the GH transcript was observed in association to reduced migration rate of the GH transcript and increased mRNA content in the dark-cycle period.

SIGNIFICANCE

Our findings provide evidence that changes in the GH mRNA poly(A) length may underlie the circadian pattern of GH mRNA and protein levels in the pituitary gland of rats.

Rhythmic control of activity and sleep by class B1 GPCRs

Members of the class B1 family of G-protein coupled receptors (GPCRs) whose ligands are neuropeptides have been implicated in regulation of circadian rhythms and sleep in diverse metazoan clades. This review discusses the cellular and molecular mechanisms by which class B1 GPCRs, especially the mammalian VPAC2 receptor and its functional homologue PDFR in Drosophila and C. elegans, regulate arousal and daily rhythms of sleep and wake. There are remarkable parallels in the cellular and molecular roles played by class B1 intercellular signaling pathways in coordinating arousal and circadian timekeeping across multiple cells and tissues in these very different genetic model organisms.

Exercise-Induced growth hormone during acute sleep deprivation

The effect of acute (24‐h) sleep deprivation on exercise‐induced growth hormone (GH) and insulin‐like growth factor‐1 (IGF‐1) was examined. Ten men (20.6 ± 1.4 years) completed two randomized 24‐h sessions including a brief, high‐intensity exercise bout following either a night of sleep (SLEEP) or (24‐h) sleep deprivation (SLD). Anaerobic performance (mean power [MP], peak power [PP], minimum power [MinP], time to peak power [TTPP], fatigue index, [FI]) and total work per sprint [TWPS]) was determined from four maximal 30‐sec Wingate sprints on a cycle ergometer. Self‐reported sleep 7 days prior to each session was similar between SLEEP and SLD sessions (7.92 ± 0.33 vs. 7.98 ± 0.39 h, P =0.656, respectively) and during the actual SLEEP session in the lab, the total amount of sleep was similar to the 7 days leading up to the lab session (7.72 ± 0.14 h vs. 7.92 ± 0.33 h, respectively) (P =0.166). No differences existed in MP, PP, MinP, TTPP, FI, TWPS, resting GH concentrations, time to reach exercise‐induced peak GH concentration (TTP), or free IGF‐1 between sessions. GH area under the curve (AUC) (825.0 ± 199.8 vs. 2212.9 ± 441.9 μg/L*min, P <0.01), exercise‐induced peak GH concentration (17.8 ± 3.7 vs. 39.6 ± 7.1 μg/L, P <0.01) and ΔGH (peak GH – resting GH) (17.2 ± 3.7 vs. 38.2 ± 7.3 μg/L, P <0.01) were significantly lower during the SLEEP versus SLD session. Our results indicate that the exercise‐induced GH response was significantly augmented in sleep‐deprived individuals.

Human growth hormone release is heavily influenced by sleep and exercise. Our study shows that sleep deprivation dramatically augments the exercise‐induced human growth hormone response.

Growth hormone/insulin-like growth factor-I axis in obstructive sleep apnea syndrome: an update

Obstructive sleep apnea syndrome (OSAS) is a serious, prevalent condition that has significant mortality and morbidity when untreated. It is strongly associated with obesity and is characterized by changes in the serum levels or secretory patterns of several hormones. In particular, obese patients with OSAS show a peculiar reduction of both spontaneous and stimulated GH secretion coupled with reduced IGF-I concentrations and impaired peripheral sensitivity to GH. These endocrine abnormalities are more marked than those observed in non-apneic obese subjects, and are likely to be due to the effects of hypoxia and sleep fragmentation on hormone secretory pattern. The GH/IGF-I axis activity disruption can be responsible, at least in part, for metabolic alterations, which are common in OSAS and increase the risk of cardiovascular events as well as mortality. Effective assessment and management of OSAS may correct endocrine changes, improve quality of life, and prevent associated morbidity or death.

Neuroendocrine alterations in obese patients with sleep apnea syndrome

Obstructive sleep apnea syndrome (OSAS) is a serious, prevalent condition that has significant morbidity and mortality when untreated. It is strongly associated with obesity and is characterized by changes in the serum levels or secretory patterns of several hormones. Obese patients with OSAS show a reduction of both spontaneous and stimulated growth hormone (GH) secretion coupled to reduced insulin-like growth factor-I (IGF-I) concentrations and impaired peripheral sensitivity to GH. Hypoxemia and chronic sleep fragmentation could affect the sleep-entrained prolactin (PRL) rhythm. A disrupted Hypothalamus-Pituitary-Adrenal (HPA) axis activity has been described in OSAS. Some derangement in Thyroid-Stimulating Hormone (TSH) secretion has been demonstrated by some authors, whereas a normal thyroid activity has been described by others. Changes of gonadal axis are common in patients with OSAS, who frequently show a hypogonadotropic hypogonadism. Altogether, hormonal abnormalities may be considered as adaptive changes which indicate how a local upper airway dysfunction induces systemic consequences. The understanding of the complex interactions between hormones and OSAS may allow a multi-disciplinary approach to obese patients with this disturbance and lead to an effective management that improves quality of life and prevents associated morbidity or death.

EFFECT OF MULTI-FUNCTIONAL FABRIC ON SLEEP STAGES AND GROWTH HORMONE LEVELS DURING SLEEP

Nine young girls participated in cross-over sessions, sleeping with either multi-functional fabric (experimental session) or cotton (control session). The relative duration of slow-wave sleep (SWS) was 1.89-fold higher in the experimental session than in the control session. The peak growth hormone (GH) secretion in the experimental session was more than 2.4-fold higher than during the control session (p <.001). The quality of sleep during the experimental session was significantly better than in the control session (p <.01). These results suggest that multi-functional fabric wear is effective in inducing deep sleep, increasing GH, and improving the quality of sleep.

Effects of growth hormone on glucose, lipid, and protein metabolism in human subjects

In evolutionary terms, GH and intracellular STAT 5 signaling is a very old regulatory system. Whereas insulin dominates periprandially, GH may be viewed as the primary anabolic hormone during stress and fasting. GH exerts anabolic effects directly and through stimulation of IGF-I, insulin, and free fatty acids (FFA). When subjects are well nourished, the GH-induced stimulation of IGF-I and insulin is important for anabolic storage and growth of lean body mass (LBM), adipose tissue, and glycogen reserves. During fasting and other catabolic states, GH predominantly stimulates the release and oxidation of FFA, which leads to decreased glucose and protein oxidation and preservation of LBM and glycogen stores. The most prominent metabolic effect of GH is a marked increase in lipolysis and FFA levels. In the basal state, the effects of GH on protein metabolism are modest and include increased protein synthesis and decreased breakdown at the whole body level and in muscle together with decreased amino acid degradation/oxidation and decreased hepatic urea formation. During fasting and stress, the effects of GH on protein metabolism become more pronounced; lack of GH during fasting increases protein loss and urea production rates by approximately 50%, with a similar increase in muscle protein breakdown. GH is a counterregulatory hormone that antagonizes the hepatic and peripheral effects of insulin on glucose metabolism via mechanisms involving the concomitant increase in FFA flux and uptake. This ability of GH to induce insulin resistance is significant for the defense against hypoglycemia, for the development of "stress" diabetes during fasting and inflammatory illness, and perhaps for the "Dawn" phenomenon (the increase in insulin requirements in the early morning hours). Adult patients with GH deficiency are insulin resistant-probably related to increased adiposity, reduced LBM, and impaired physical performance-which temporarily worsens when GH treatment is initiated. Conversely, despite increased LBM and decreased fat mass, patients with acromegaly are consistently insulin resistant and become more sensitive after appropriate treatment.

Sleep deprivation suppresses neurogenesis in the adult hippocampus of rats

We reported previously that 96 h of sleep deprivation (SD) reduced cell proliferation in the dentate gyrus (DG) of the hippocampus in adult rats. We now report that SD reduces the number of new cells expressing a mature neuronal marker, neuronal nuclear antigen (NeuN). Rats were sleep-deprived for 96 h, using an intermittent treadmill system. Total sleep time was reduced to 6.9% by this method in SD animals, but total treadmill movement was equated in SD and treadmill control (CT) groups. Rats were allowed to survive for 3 weeks after 5-bromo-2-deoxyuridine (BrdU) injection. The phenotype of BrdU-positive cells in the DG was assessed by immunofluorescence and confocal microscopy. After 3 weeks the number of BrdU-positive cells was reduced by 39.6% in the SD group compared with the CT. The percentage of cells that co-localized BrdU and NeuN was also lower in the SD group (SD: 46.6 +/- 1.8% vs. CT: 71.9 +/- 2.1, P < 0.001). The percentages of BrdU-labeled cells co-expressing markers of immature neuronal (DCX) or glial (S100-beta) cells were not different in SD and CT groups. Thus, SD reduces neurogenesis in the DG by affecting both total proliferation and the percentage of cells expressing a mature neuronal phenotype. We hypothesize that sleep provides anabolic or signaling support for proliferation and cell fate determination.

Light treatment and circadian adaptation to shift work

Work at unconventional hours can have both long and short term consequences. Shift workers are often required to perform their duties at times that are not favoured by the body's endogenous clock, or circadian pacemaker. A typical night shift worker, for example, may report reductions in alertness and performance during shifts, or significant difficulty attaining sleep of recuperative value in the day, all the while being more likely to develop health complications. The study of circadian physiology has significantly contributed to our current ability to aid the shift worker deal with atypical schedules. We discuss the usefulness of light treatment as a countermeasure for maladaptation to atypical work schedules.

GHRH and sleep

A significant portion of the total daily growth hormone (GH) secretion is associated with deep non-REM sleep (NREMS). GH secretion is stimulated by the hypothalamic neurohormone, GH-releasing hormone (GHRH). Exogenous GHRH promotes NREMS in various species. Suppression of endogenous GHRH (competitive antagonist, antibodies, somatostatinergic stimulation, high doses of GH or insulin-like growth factor) results in simultaneous inhibition of NREMS. Mutant and transgenic animals with a defect in GHRHergic activity display permanently reduced NREMS which cannot be reversed by means of GH supplementation. GHRH contents and mRNA levels in the hypothalamus correlate with sleep-wake activity during the diurnal cycle and sleep deprivation and recovery sleep. Stimulation of NREMS by GHRH is a hypothalamic action. GABAergic neurons in the anterior hypothalamus/preoptic region are candidates for mediating promotion of NREMS by GHRH. In contrast to NREMS, stimulation of REMS by GHRH is mediated by GH. Simultaneous stimulation of NREMS and GH secretion by GHRH may promote adjustment of tissue anabolism to sleep.

Reductions in circulating anabolic hormones induced by sustained sleep deprivation in rats

The main systemic disorders resulting from prolonged sleep deprivation in laboratory animals are a negative energy balance, low circulating thyroid hormones, and host defense impairments. Low thyroid hormones previously have been found caused by altered regulation at the level of the hypothalamus with possible pituitary involvement. The present studies investigated the effects of sleep deprivation on other major anabolic hormonal systems. Plasma growth hormone (GH) concentrations and major secretory bursts were characterized. Insulin-like growth factor I (IGF-I) was evaluated as an integrative marker of peripheral GH effector activity. Prolactin (PRL) was assessed by basal concentrations and by stimulating the pituitary with exogenous thyrotropin-releasing hormone. Leptin was studied for its linkage to metabolic signs of sleep loss and its correspondence to altered neuroendocrine regulation in other disease states. Last, plasma corticosterone was measured to investigate the degree of hypothalamic-pituitary-adrenal activation. Sleep deprivation was produced by the disk-over-water method, a well-established means of selective deprivation of sleep and noninterference with normal waking behaviors. Hormone concentrations were determined in sham comparisons and at intervals during baseline and experimental periods lasting at least 15 days in partially and totally sleep-deprived rats. The results indicate that high-amplitude pulses of GH were nearly abolished and that concentrations of GH, IGF-I, PRL, and leptin all were suppressed by sleep deprivation. Corticosterone concentration was relatively unaffected. Features of these results, such as low GH and low IGF-I, indicate failed negative feedback and point to hypothalamic mechanisms as containing the foci responsible for peripheral signs.

Ageing, growth hormone and physical performance

Human ageing is associated to a declining activity of the GH/IGF-I axis and to several changes in body composition, function and metabolism which show strict similarities with those of younger adults with pathological GH deficiency. The age-related changes of the GH/IGF-I axis activity are mainly dependent on age-related variations in the hypothalamic control of somatotroph function, which is also affected by changes in peripheral hormones and metabolic input. The term "somatopause" indicates the potential link between the age-related decline in GH and IGF-I levels and changes in body composition, structural functions and metabolism which characterise ageing. Physical exercise is an important environmental regulator of the GH/IGF-I axis activity. Increased physical fitness and regular training increase GH production in adults, while the GH response to aerobic or resistance exercise is reduced with age. In older subjects regular exercise has the potential to improve overall fitness and quality of life and is also associated to decreased morbidity and increased longevity. Similar effects are seen following GH therapy in adult deficiency. This assumption led to clinical trials focusing on rhGH and/or rhlGF-I as potential anabolic drug interventions in elderly subjects. To restore the activity of GH/IGF-I axis with anabolic, anti-ageing purposes, attention has been also paid to GH-releasing molecules such as GHRH, orally active synthetic GH-secretagogues (GHS) and, more recently, to the endogenous natural GHS, ghrelin, which exerts several important biological actions, including the regulation of metabolic balance and orexigenic effects. At present, however, there is no definite evidence that "frail" elderly subjects really benefit from restoring GH and IGF-I levels within the young adult range by treatment with rhGH, rhlGF-I, GHRH or GHS. In this article the alteration of the GH/IGF-I axis activity during ageing is revised taking into account the role of physical activity as a regulator of the axis function and considering the effects of the restoration of GH and IGF-I circulating levels on body composition and physical performance.

Polysomnographic findings in five adult patients with pituitary insufficiency before and after cessation of human growth hormone replacement therapy

OBJECTIVE

We observed the new onset of severe obstructive sleep apnoea syndrome (OSAS) in an adult male patient during human growth hormone (hGH) replacement therapy. This prompted us to evaluate the potential influence of hGH substitution therapy on sleep in middle-aged men.

DESIGN

A longitudinal study.

SUBJECTS

Five male patients (aged 44-56 years, median age 54 years) with postoperative pituitary insufficiency given hGH replacement therapy for 1-2 years (median dose 2.0 U/day; median IGF-I serum concentration 351 microg/l) and 6 months after cessation of hGH treatment (median IGF-I level 77 microg/l - 1 microg/l = 0.131 nmol/l).

MEASUREMENTS

Polysomnographic studies were performed, and the following parameters were determined: time in bed (TIB), sleep period time (SPT), total sleep time (TST), sleep efficiency (SE = TST/TIB), sleep stage 1 onset latency (SL), different sleep stages [W (wake), S1, S2, SWS (slow wave sleep = S3 + S4) and REM; % of SPT], stage shifts per hour of SPT (SS/h), stage shifts to W/h of SPT [A/h (awakening)], index of apnoea and hypopnoea events per hour of TST (AH/h), arousals from apnoea and hypopnoea per hour of TST (Ar/h), index of obstructive (OAH/h), central (CAH/h) and mixed (MAH/h) events of apnoea and hypopnoea per hour of TST and minimal desaturation (MD).

RESULTS

Median baseline results were: TIB, 479 min; SPT, 465 min; TST, 405 min; SE, 77%; SL, 8.5 min; W, 18.9%; S1, 8.2%; S2, 52.7%; REM, 13.5%; SS/h, 17.7; A/h, 2.8; AH/h, 11.9; Ar/h, 4.4; MD, 80%. These parameters did not change significantly after cessation of hGH treatment. In contrast, median SWS decreased significantly from 33 min (7.1%) to 7.5 min (1.8%; P = 0.03). Median OAH/h decreased significantly from 4.4 to 0.1 (P = 0.03) whereas CAH/h increased from 6.3 to 14.6 (P = 0.03) after cessation of hGH. Correspondingly, one patient with OSAS improved markedly whereas another patient developed new and asymptomatic central SAS after cessation of hGH.

CONCLUSION

This study showed that hGH replacement therapy influenced sleep reaction in a complex way in middle-aged men; cessation of treatment was associated with a significant decrease in slow wave sleep and a shift from obstructive to central apnoea and hypopnoea.

Growth hormone secretion during sleep in male depressed patients

1. Growth hormone (GH) secretion during sleep was studied in ten male patients with major depression according to DSM III and eight normal controls. 2. Samples were collected through a continuous blood withdrawal pump while sleep was recorded in the laboratory. 3. The results showed a marked decrease in the GH secretion mainly during the first three hours of sleep in depressed patients as compared to normal controls. DST and TRH tests were also administered to the same patients but no correlation was observed between a positive test and a blunted GH secretion, suggesting that the various neuroendocrinological disturbances do not coexist in all depressed patients. 4. This disturbance in GH secretion during sleep, along with reduced slow wave sleep (SWS), gives support to the theory that GHRH is the common stimulus of SWS and GH release and that the ratio of GHRH and its counterpart CRH plays a major role in the pathophysiology of disturbed endocrine activity during sleep in depression.

Effects of systemic GHRH on sleep in intact and hypophysectomized rats

The role of pituitary growth hormone (GH) in the mediation of enhanced sleep elicited by GH-releasing hormone (GHRH) was studied in the rat. Intact and hypophysectomized (HYPOX) rats received systemic injections of GHRH or physiological saline. GHRH (0.5, 5.0, or 50 micrograms/kg in the intact rats and 0.5 or 50 micrograms/kg in HYPOX rats) was injected 6 h after light onset (P.M. injection) or just before light onset (A.M. injection, 0.5 microgram/kg in both A.M. groups). Sleep-wake activity and brain cortical temperature were recorded for 23 h (12 h light + 11 h dark). A.M. injection of GHRH did not alter sleep in normal or HYPOX rats. Each dose of P.M. GHRH increased rapid-eye-movement sleep (REMS) during 6 h postinjection in the intact rats. Hypophysectomy abolished the REMS-promoting activity of GHRH. P.M. injection of 0.5 microgram/kg GHRH increased non-REM sleep (NREMS) and enhanced electroencephalogram slow-wave activity during NREMS in both the intact and the HYPOX rats. The NREMS-promoting activity disappeared when the dose of GHRH was increased in the intact rats, whereas a tendency to enhanced NREMS was still observed after 50 micrograms/kg GHRH in the HYPOX rats. GHRH stimulated GH secretion dose dependently in the intact rats. A.M. injection of 0.5 microgram/kg GHRH tended to be less effective in stimulating GH release than the same dose administered P.M. The results confirm the time-of-day variations in the GHRH effects on sleep previously reported in human subjects. It is likely that pituitary GH is involved in the mediation of the REMS-promoting activity of GHRH but not in the NREMS-promoting activity of GHRH. Nevertheless, the results do not exclude the possibility that GH may modulate NREMS.

Influence of partial sleep deprivation on the secretion of thyrotropin, thyroid hormones, growth hormone, prolactin, luteinizing hormone, follicle stimulating hormone, and estradiol in healthy young women

The influence of partial sleep deprivation during the second half of the night on the secretion of thyroid stimulating hormone (TSH), thyroxin (T4), free T4 (fT4), triiodothyronine (T3), prolactin (PRL), growth hormone (GH), luteinizing hormone (LH), follicle stimulating hormone (FSH), and estradiol (E2) was investigated in 10 healthy young women. Blood samples were drawn at hourly intervals over a 64-hour period (i.e., 3 consecutive days and nights). During night 2, all subjects were awakened at 1:30 a.m. During partial sleep deprivation, TSH concentrations increased significantly and remained elevated throughout the following day. Levels of T4, fT4, and T3 were enhanced during the partial sleep deprivation hours only, and changes in these hormones seemed to be independent of TSH. PRL levels decreased, LH and E2 concentrations increased, and GH and FSH secretion remained unchanged during partial sleep deprivation. This pattern of change of different endocrine axes during partial sleep deprivation resembles those seen after total sleep deprivation, suggesting that similar neurochemical changes are induced by both forms of antidepressant therapy. The late evening GH peak occurred almost exclusively before the onset of sleep. Partial sleep deprivation did not influence the chronobiological profiles of any of the hormones investigated. The chemical changes underlying these alterations are speculated to involve enhancement of central norepinephrine and dopamine activity with a concomitant increase in the activity of the sympathetic nervous system.

Delta sleep-inducing peptide administration does not influence growth hormone and prolactin secretion in normal women

The aim of this study was to analyze the effects of delta sleep-inducing peptide (DSIP) on growth hormone (GH) and prolactin (PRL) secretion in eight healthy women with normal cycles (aged 17-36 years). GH and PRL secretion was studied in five women after DSIP (25 micrograms/kg bw IV over 30 min), arginine chlorhydrate (0.5 g/kg bw IV over 30 min) and simultaneous DSIP plus arginine chlorhydrate administration. In three other women the circadian rhythm of GH and PRL was studied during DSIP (25 micrograms/kg bw from 2130h to 2230h) and placebo IV infusion. Serum GH and PRL levels were normal under basal conditions and no effects were noted after the infusion of DSIP. The GH and PRL circadian rhythm was not modified by DSIP administration. DSIP did not influence GH and PRL responsiveness to arginine chlorhydrate. We found that at dosages which are known to modify ECG patterns, DSIP is unable to modify spontaneous or arginine chlorhydrate-induced GH and PRL secretion.

The potential relevance of growth hormone to female reproductive physiology and pathophysiology

OBJECTIVE

To assess possible interfacing between the somatotrophic and reproductive axes.

DESIGN

Literature review.

MAIN OUTCOME MEASURES

Ovarian growth hormone reception and action.

RESULTS

The available literature strongly supports a permissive role for the somatotrophic axis in the reproductive process.

CONCLUSIONS

Although a role for growth hormone in reproductive biology appears highly likely, its relevance to the process of puberty and to the normal workings of the menstrual cycle, as well as its possible application in reproductive pathology must await further investigation.

Inhibition of growth hormone-releasing factor suppresses both sleep and growth hormone secretion in the rat

To study the possible involvement of hypothalamic growth hormone-releasing factor (GRF) in sleep regulation, a competitive GRF-antagonist, the peptide (N-Ac-Tyr1,D-Arg2)-GRF(1-29)-NH2, was intracerebroventricularly injected into rats (0.003, 0.3, and 14 nmol), and the EEG and brain temperature were recorded for 12 h during the light cycle of the day. Growth hormone (GH) concentrations were determined from plasma samples taken at 20-min intervals for 3 h after 14 nmol GRF-antagonist. The onset of non-rapid eye movement sleep (NREMS) was delayed in response to 0.3 and 14 nmol GRF-antagonist, the duration of NREMS was decreased for one or more hours and after 14 nmol EEG slow wave amplitudes were decreased during NREMS in postinjection hour 1. The high dose of GRF-antagonist also suppressed REMS for 4 h, inhibited GH secretion, and elicited a slight biphasic variation in brain temperature. These findings, together with previous observations indicating a sleep-promoting effect for GRF, support the hypothesis that hypothalamic GRF is involved in sleep regulation and might be responsible for the correlation between NREMS and GH secretion reported in various species.

Reproducibility of 24-hour serum growth hormone profiles in man

OBJECTIVE

To study the reproducibility of 24-h serum growth hormone (GH) concentration profiles in adults.

DESIGN

24-h serum GH concentrations were constructed by drawing blood samples at 20-min intervals. Four study occasions over a period of 1 year were chosen to assess the reproducibility.

SUBJECTS

Six healthy adult male volunteers of normal height and weight and aged between 20 and 22 years.

MEASURES

The resulting GH data arrays were analysed by Fourier transformation. Between and within individual variations were calculated and expressed in terms of coefficients of variation and data plotted to show variations between groups and individuals.

RESULTS

The frequency component of GH secretion occurred with a dominant periodicity of between 160 and 240 min. Precise estimates of spectral power (strength of oscillatory activity) and period were obtained for group data, but such estimates cannot be inferred from a single profile. There was no significant difference in 24-h mean serum GH concentration over the year of study: occasion 1 (February) mean 2.0 mU/l (SD 0.5); occasion 2 (March) mean 3.7 mU/l (SD 2.8); occasion 3 (July) mean 2.7 mU/l (SD 1.4); occasion 4 (February) 2.5 mU/l (SD 1.5) (mean within individual coefficient of variation 35%, range 9-58). The concentrations of factors known to influence GH synthesis and secretion, insulin-like growth factor I, thyroxine, testosterone and oestradiol, varied little over the year of study.

CONCLUSIONS

These data demonstrate that group data are reproducible in terms of oscillatory activity and the amount of GH secreted and that 24-h GH profiles should be used predominantly for analysing group data. The variability between individual profiles limits their value in the investigation of children with growth failure and suspected GH insufficiency.

Neuroendocrinological investigations during sleep deprivation in depression. I. Early morning levels of thyrotropin, TH, cortisol, prolactin, LH, FSH, estradiol, and testosterone

Measurements of 12 hormones were conducted in patients with major depressive disorder at 8 AM on the morning before and at 8 AM on the morning after total sleep deprivation (SD). Thyrotropin (TSH), thyroxine (T4), triiodothyronine (T3), and free T3 (fT3) were measured in 50 patients, free T4 in 39 patients, reverse T3, cortisol, prolactin, luteinizing hormone, and follicle-stimulating hormone in 21, estradiol in 20 (women), and testosterone in 14 (men). After SD, there was a significant rise in TSH, T4, T3, and fT3 concentrations and a significant fall in testosterone levels. The increases in TSH levels were significantly correlated to clinical response. Responders to SD had higher T4, fT4, rT3, and testosterone concentrations before SD. Neither age, gender, polarity, nor antidepressant medication had a clearly significant effect on the response to SD.

Neuroendocrinological investigations during sleep deprivation in depression. II. Longitudinal measurement of thyrotropin, TH, cortisol, prolactin, GH, and LH during sleep and sleep deprivation

Thyrotropin (TSH), thyroxin (T4), triiodothyronine (T3), free T3 (fT3), cortisol, prolactin, and human growth hormone (HGH) were measured every 2 hr during a night of sleep, the following day, and a night of sleep deprivation (SD) in 14 patients with major depressive disorder. In subgroups fT4 (n = 5), reverse T3 (rT3), and luteinizing hormone (LH) (n = 6) were also investigated. Significant increases in TSH, T4, fT4, T3, fT3, rT3, and cortisol and decreases in prolactin levels occurred during the night of SD, compared to the pattern during the night of sleep. The pre-SD T4 and T3 levels of the responders to SD were already higher than in the nonresponders, and increased less during SD. The cortisol and HGH concentrations of the responders rose higher during SD than those of the nonresponders. Changes in TSH and prolactin were not correlated to clinical response. Analysis of possible neurochemical mechanisms underlying this "pattern" of changes in different endocrine profiles suggests that enhanced noradrenergic activity might play a role in the changes in TSH, cortisol, thyroid hormones, and possibly HGH secretion during SD, and increased dopaminergic tone probably induced the decline in prolactin levels. Additional effects of the serotonergic system cannot be excluded at present. In conclusion, the data suggest that enhanced noradrenergic activity of the locus coeruleus stimulates alpha and/or beta adrenergic receptors in depressed patients during SD. This mechanism could well be involved in the antidepressant effect of this therapy.

Responsiveness of rats to interleukin-1: effects of monosodium glutamate treatment of neonates

Monosodium glutamate (MSG) treatment of neonatal rats results in degenerative lesions of the medial basal hypothalamus, particularly the arcuate nucleus (AN). The AN is rich in corticotropin-releasing hormone (CRF) and adrenocorticotrophic hormone/alpha-melanocyte-stimulating hormone (alpha-MSH). These substances are part of a negative feedback mechanism for the regulation of interleukin-1 (IL1), a cytokine with diverse biologic actions including a role in sleep regulation. The purpose of these experiments was to determine the effects of exposure of neonatal rats to MSG on their responsiveness as adults to IL1. Adult rats, treated as neonates with MSG or the saline, were injected intracerebroventricularly during the light phase with three doses of IL1 (2.5, 10.0, 25.0 ng) and sleep-wake activity determined and brain temperature recorded for the next 6 hr. IL1 administration induced fever in both treatment groups at each dose of IL1 tested, and the febrile response of the MSG rats to the 25.0 ng dose of IL1 was greater than that of the saline control rats. In saline-treated rats, the 2.5 ng dose of IL1 enhanced non-rapid-eye-movement sleep (NREMS) without affecting rapid-eye-movement sleep (REMS) or wakefulness, whereas the 25.0 ng dose of IL1 inhibited both NREMS and REMS. In contrast, only the 10.0 ng dose of IL1 altered NREMS in MSG-treated rats. These results support the hypothesis that CRF- and alpha-MSH-containing perikarya are involved in regulation of IL1 actions.

Nocturnal growth hormone surges in type 1 diabetes mellitus are both sleep- and glycemia-dependent: assessment under continuous sleep monitoring

Our work has studied the relationship between nocturnal growth hormone (GH) surges, sleep and glycemia in seven conventionally treated type 1 diabetic patients under continuous sleep monitoring and the results were compared to those found in five age-matched healthy controls. On the experimental day, sleep was monitored from 24.00 to 07.00. Blood glucose levels and GH were assayed in both groups. As a group the diabetics had nocturnal GH responses higher than those in controls. However, the sleep-related GH release is not abnormally high in patients who maintain strict normoglycemia. Early-night hypoglycemia and/or rapidly decreasing blood glucose concentrations enhance sleep-related GH secretion in diabetics, whereas hypoglycemia not associated with slow-wave sleep (SWS) causes a moderate increase in GH. Late-onset nocturnal hypoglycemia is not potent enough to stimulate GH. It is proposed that in diabetics sleep-related GH production is probably not abnormally elevated within a wide range of stable glucose levels, but when these thresholds are crossed or when there is a rapid decrease in blood glucose, then GH secretion is inversely related to the changing blood glucose. Therefore, our study supports the conclusion that sleep-related GH secretion is finely modulated by the actual glycemic fluctuations in diabetic patients.

Electroencephalographic sleep in schizophrenia: a critical review

Several polysomnographic abnormalities seem to occur consistently in schizophrenic patients: impaired sleep continuity and reduced total sleep, reduced amounts of slow wave sleep, and reduced rapid eye movement (REM) sleep latency and defective REM rebound following REM deprivation. None of these findings is specific for schizophrenia, and only a subgroup of schizophrenic patients seem to have these abnormalities. It appears that reduced slow wave sleep may be related to a neurodevelopmental disorder related to the defect state in schizophrenia. The pathophysiological significance of the defective REM rebound and the REM sleep abnormalities in schizophrenia remain uncertain. Carefully designed studies are needed to further characterize the sleep disturbance in schizophrenia and to study them in relation to other, known pathophysiological changes in this disorder.

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.

Sleep disorders in Tourette's syndrome

Sleep disorders have been reported in approximately 80% of Tourette's syndrome (TS) patients. Sleep studies in TS patients have demonstrated a 30% reduction in delta-sleep (slow-wave sleep) in nontreated subjects, decreased percentage of REM-sleep and the presence of tics during sleep. A subgroup of young TS patients was reported to have an increased percentage of delta sleep. Although these findings were initially thought to result from deranged dopaminergic and serotoninergic functions in TS, we suggest that abnormalities of hypothalamic-mediated control mechanisms involving the intrinsic opioids may also account for the observed derangements in sleep-wave patterns in TS patients. Evidence for impaired hypothalamic regulation in TS patients includes our preliminary observations of abnormal growth-hormone release to administration of the opiate antagonist naloxone in TS. These data further suggest an interrelationship of neurochemical mechanisms involving opioid-mediated hyperactivity, slow-wave sleep and growth hormone at the level of the hypothalamus.

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.

Delta sleep-inducing peptide (DSIP) stimulates growth hormone (GH) release in the rat by hypothalamic and pituitary actions

To evaluate possible effects of delta sleep-inducing peptide on GH release, the peptide was micro-injected into conscious animals with third ventricular cannulae and blood samples were drawn from indwelling external jugular vein cannulae. Ovariectomized animals were used in order to eliminate gonadal steroid feedback. In the initial experiment, intraventricular injection of 5 micrograms of the peptide induced an elevation of GH which became significant by 30 min and persisted for the 120 min duration of the experiment after the injection. Diluent-injected animals showed a slight initial drop in GH and then no increase. The increase in plasma GH induced by the peptide was dose-related with a minimal effective dose of 0.1 microgram and a linear log-dose increase to a dose of 10 micrograms. This effect is presumably mediated hypothalamically via a dopaminergic mechanism since it could be blocked by pre-treatment of the animals with pimozide, a dopamine receptor blocker. Dispersed overnight, cultured pituitary cells from ovariectomized rats exhibited a dose-related increase in GH release in static incubations with DSIP. A response occurred with the lowest dose tested (10(-12) M) which increased to a maximum at 10(-10) M DSIP. The responses then declined at higher doses such that they were no longer significant at doses of 10(-7) and 10(-5) M. The increase even at the most effective dose was approximately 50% above the basal values. The results are consistent with the hypothesis that DSIP may be involved in GH release via a dopaminergic mechanism.(ABSTRACT TRUNCATED AT 250 WORDS)

Temporal correlation of some endocrine circadian rhythms in elderly subjects

The aim of this chronobiological study was to investigate temporal correlations in the circadian patterns of 6 hormones, namely somatotrophic hormone (STH), prolactin (PRL), cortisol (F), aldosterone (ALD), insulin (IRI) and C-peptide (CP), assayed in systemic blood serum drawn at 07:00, 10:00, 13:00, 16:00, 19:00 and 22:00 h from an antecubital vein in 19 young subjects (aged 20-29 yr, comprising 10 males and 9 females; and 20 elderly subjects (aged 70-81 yr, comprising 10 males and 10 females). All subjects were sampled on a normal dietary sodium intake (120-140 mEq/24h) while following a social routine of diurnal activity (07:00-23:00) and nocturnal rest (23:00-07:00). Time-qualified data were analyzed by lead-lag correlation and by cosinor analysis. According to the lead-lag correlation findings, it would appear that the correlation which exists between several time-qualified series in young subjects is no longer present in elderly subjects. The circadian rhythms which were found to have lost their temporal correlations with advancing age were those between STH and IRI, STH and ALD, PRL and IRI, PRL and CP, and ALD and CP. It should be noted that the correlation between hormonal rhythms breaks down mainly on account of a peculiar age-related change in the magnitude of the circadian fluctuation. This chronological decline in amplitude led to the conclusion that the senescence of endocrine rhythmic functions is a biological phenomenon characterized by altered circadian variability.

Hypothalamic control of GH secretion: pathophysiology and clinical implications

GH is secreted episodically. Its pattern is regulated by the interplay of a releasing and a release-inhibiting hormone of hypothalamic origin. Modulation occurs by metabolic factors (glucose, free fatty acids, ketone bodies, amino acids). Altered GH secretion has been observed in states of metabolic derangement such as diabetes mellitus, malnutrition and obesity. Further modulation occurs by extrahypothalamic CNS structures. In man--but not in animals, including subhuman primates--sleep has an important effect on GH secretion. A defective GH secretory pattern has been found to occur in several states of sleep disturbance, such as sleep deprivation, narcolepsy, severe psychosocial derangement, the apallic syndrome. Other CNS influences on GH secretion are related to stress, emotional changes and psychiatric disturbances. The exact mechanisms by which most of these influences are relayed to the GH secretory apparatus of the hypothalamus remain yet to be investigated.