Effects of hormones on sleep

Causal relationship between insomnia and thyroid disease: A bidirectional Mendelian randomization study

OBJECTIVE

Some correlations between thyroid disorders and insomnia have been found in previous studies; however, the causal relationship between them is unclear. The aim of this study was to investigate the causal relationship between insomnia and five thyroid disorders (hyperthyroidism, hypothyroidism, thyroiditis, thyroid nodules, and thyroid cancer).

METHODS

We assessed the causal relationship between insomnia and thyroid disorders using inverse variance weighted, weighted median, and Mendelian randomization (MR)-Egger analyses in MR analyses and then used inverse MR analyses to assess the causal relationship between thyroid disorders and insomnia.

RESULTS

MR analysis showed that insomnia did not increase the risk of hyperthyroidism, hypothyroidism, thyroiditis, thyroid nodules, and thyroid cancer. However, reverse MR analysis showed that thyroid cancer increased the risk of insomnia (OR = 1.01, 95%CI: 1.00-1.02, p = .01), and the other four thyroid disorders had no direct causal relationship with insomnia. Sensitivity analyses indicated that the results were robust and no pleiotropy or heterogeneity was detected.

CONCLUSION

This study did not find evidence of a bidirectional causal relationship between genetically predicted insomnia and hyperthyroidism, hypothyroidism, thyroiditis, and thyroid nodules. However, we found that although insomnia does not increase the risk of thyroid cancer, thyroid cancer does increase the risk of insomnia.

Association between phthalates and sleep problems in the U.S. adult females from NHANES 2011-2014

There is little research on the relationship between phthalates exposure and sleep problems in adult females, with existing studies only assessing the association between exposure to individual phthalates with sleep problems.     We aimed to analyse the relationship between phthalates and sleep problems in 1366 US females aged 20 years and older from the 2011-2014 National Health and Nutrition Examination Survey (NHANES) by age stratification. Multivariate logistic regression showed that the fourth quartile of MECPP increased the risk of sleep problems in females aged 20-39 compared with the reference quartile (OR: 1.87, 95% CI: 1.14, 3.08). The WQS index was significantly associated with the sleep problems in females aged 20-39. In the BKMR, a positive overall trend between the mixture and sleep problems in females aged 20-39. In this study, we concluded that phthalates might increase the risk of sleep problems in females aged 20-39.

The relationship between sleep duration and thyroid function in the adult US population: NHANES 2007-2012

OBJECTIVE

Sleep disturbance is a common problem in the general population. Sleep deprivation or dysfunction can have profound health consequences. However, how sleep duration is associated with thyroid function remains unclear. This study was thus developed to examine the association between sleep duration and thyroid function in the US adult population.

METHODS

A total of 8102 participants from the NHANES 2007-2012 dataset were included in this study. Weighted data analyses were conducted, and the link between sleep duration and thyroid function was probed using linear regression models with smoothed curve fitting. Stratified analyses were also performed.

RESULTS

Weighted mean (standard deviation) values for study variables were as follows: sleep duration 6.85 (0.02) hours, thyroid-stimulating hormone (TSH) 1.86 (0.03) mIU/ml, serum free T3 3.20 (0. 01) pg/mL, serum free T4 0.80 (0.01) ng/dL, serum total T3 115.12 (0.64) ng/dL, serum total T4 7.81 (0.04) ug/dL, TPOAb 16.20 (1.53) IU/mL, TgAb 5.75 (0.73) IU/mL, and Tg 15.11 (0.46) ng/mL. In unadjusted analyses, increased sleep duration was associated with higher serum TSH levels and decreased FT3 levels. After adjustment for potential confounders, a significant negative relationship was detected between sleep duration and FT3 levels in participants with ≤7 hours of sleep. When sleep duration exceeded 7 hours, no significant changes in FT3 levels were observed after further increases in sleep duration.

CONCLUSION

Increased sleep duration was related to decreased FT3 levels, primarily at short sleep durations, and this correlation was no longer evident when participants reached the recommended healthy sleep duration.

Sleep disorders in dermatology - a comprehensive review

Sleep is a normal physiological process that accounts for approximately one third of a person's life. Disruption of the normal sleep cycle, which maintains physiological homeostasis, can lead to pathology. It is not known whether sleep disturbance causes skin disease or skin disease causes sleep impairment, but a bidirectional influence is suspected. We have compiled the data from published articles on "sleep disorders in dermatology" in PubMed Central from July 2010 to July 2022 (with the option "full text available") and provide an overview of sleep disorders associated with dermatological conditions and certain drugs used in dermatology as well as sleep disturbances for which some drugs used can cause itch or dermatological issues. Atopic dermatitis, eczema and psoriasis have been shown to be exacerbated by sleep problems and vice versa. Sleep deprivation, night-time pruritus and disrupted sleep cycles are often used to assess treatment response and quality of life in these conditions. Some medications used primarily for dermatological conditions have also been associated with alterations in the sleep-wake cycle. Addressing patients sleep disorders should be an integral part of the management of dermatological conditions. More studies are needed to further investigate the influence of sleep and skin disorders.

Urinary phthalates, phenols, and parabens in relation to sleep health markers among a cohort of Mexican adolescents

INTRODUCTION

Emerging research has shed light on the potential impact of environmental toxicants on sleep health, however, it remains unclear if these associations exist during adolescence and whether associations differ by sex. This study aimed to examine associations between phthalates, parabens, and phenols on adolescent sleep health using cross-sectional data from 470 participants from the Early Life Exposures in Mexico to Environmental Toxicants (ELEMENT) study.

MATERIAL AND METHODS

In 2015, spot urine samples were analyzed for exposure biomarkers of 14 phthalate metabolites, seven phenol, and four paraben analytes. Over seven consecutive days, sleep duration, midpoint, and fragmentation were assessed with wrist-actigraphy. We examined associations between summary phthalates, individual phthalate metabolites, and phenol and paraben analytes with mean weekday sleep duration, midpoint, and fragmentation using linear regression models adjusted for specific-gravity and sex, age, pubertal status, smoking and alcohol behavior, physical activity, and screen time.

RESULTS

Mean (SD) age was 13.8 (2.1) years; 53.5 % were female. Σ Plastic - summary measure for toxicants from plastic sources - and Σ DEHP and its metabolites, were associated with longer sleep duration in the unstratified sample. To illustrate, every 1-unit log increase in Σ DEHP was associated with 7.7 min (95 % CI: 0.32, 15.1; p < 0.05) longer duration. Summary measures of toxicants from plastic sources, personal care products, anti-androgenic toxicants, and multiple individual phthalates, phenols, and parabens were associated with later midpoint. The midpoint associations were largely female-specific. There were no associations with sleep fragmentation.

CONCLUSIONS

Higher EDC exposure may be related to longer sleep duration and later sleep timing during adolescence, and associations may vary by toxicant and according to sex.

The Hypothalamic Pituitary Thyroid Axis and Sleep

Sleep has a bidirectional relationship with the hypothalamic-pituitary-thyroid (HPT) axis, and both these homeostatic processes are inter-dependent for robust physiological functioning. The quality and quantity of sleep influence the circadian pattern of TSH and thyroid hormone secretion. Short term sleep restriction significantly reduces the amplitude of nocturnal TSH secretion and may modulate active thyroid hormone secretion, likely through an increased sympathetic tone. Conversely, TSH and active thyroid hormone affect the quantity and architecture of sleep. For instance, low TSH values are permissive for slow wave sleep and maintenance of normal sleep architecture, while the hypo- or hyper-secretion of active thyroid hormones adversely affects the quality and quantity of sleep. Structural thyroid disorders may also be associated with an altered circadian clock - a phenomenon warranting further investigation. In this review, we aim to provide readers a comprehensive review on the associations between the HPT axis and sleep patterns.

Unified Classification of Molecular, Network, and Endocrine Features of Hypothalamic Neurons

Peripheral endocrine output relies on either direct or feed-forward multi-order command from the hypothalamus. Efficient coding of endocrine responses is made possible by the many neuronal cell types that coexist in intercalated hypothalamic nuclei and communicate through extensive synaptic connectivity. Although general anatomical and neurochemical features of hypothalamic neurons were described during the past decades, they have yet to be reconciled with recently discovered molecular classifiers and neurogenetic function determination. By interrogating magnocellular as well as parvocellular dopamine, GABA, glutamate, and phenotypically mixed neurons, we integrate available information at the molecular, cellular, network, and endocrine output levels to propose a framework for the comprehensive classification of hypothalamic neurons. Simultaneously, we single out putative neuronal subclasses for which future research can fill in existing gaps of knowledge to rationalize cellular diversity through function-determinant molecular marks in the hypothalamus.

Impact of orthodontic appliances on sleep quality

INTRODUCTION

Many young patients are asked to wear headgear or functional appliances during sleep as part of their orthodontic treatment. The objective of this clinical study was to assess the impact of these appliances on sleep quality.

METHODS

Twenty-two subjects (8 boys, 14 girls) between 10 and 15 years of age wearing either a headgear or a removable appliance for 3 to 12 months were enrolled in a sleep study. Each subject participated in 2 overnight sleep studies with and without the appliance. There was a 1-week interval after an adaptation night. The studies were performed at the Sleep Research Laboratory at Toronto Western Hospital in Canada. Each subject served as his or her own control. Twelve subjects had an extraoral headgear appliance, and 10 had intraoral functional (5 Fränkel, 5 Twin-block) appliances. No subject reported any sleep or medical disorder. The primary outcome variable was sleep efficiency.

RESULTS

Sleep efficiencies were 90.7% (SD, 7.9) and 91.6% (SD, 4.3) with and without the appliances, respectively. When sleep quality was compared with and without appliances, analysis of variance (ANOVA) showed no significant difference in sleep efficiency or other sleep variables such as sleep onset latency, rapid eye movement onset latency, rapid eye movement percentage, short-wave sleep percentage, or respiratory disturbance index. Sex and body mass index were not confounding variables. In addition, the use of extraoral or intraoral appliances did not affect sleep quality.

CONCLUSIONS

In young orthodontic patients, there appears to be no difference in sleep quality with or without the overnight use of these appliances after they have been worn for a minimum of 3 months.

The effect of estrogen plus progestin treatment on sleep: a randomized, placebo-controlled, double-blind trial in premenopausal and late postmenopausal women

OBJECTIVE

In this prospective randomized, placebo-controlled and double-blind study, the objective was to investigate the effects of estrogen-progestin treatment (EPT) on sleep in pre- and postmenopausal women.

DESIGN

Seventeen premenopausal (aged 45-51 years) and 18 postmenopausal (aged 58-70 years) women were studied in a sleep laboratory for two nights (one night for adaptation and one study night) before and after 6 months of treatment with EPT or placebo. During the treatment period, premenopausal women received cyclic EPT or placebo and the postmenopausal women continuous EPT or placebo. Polysomnography and questionnaires were used to evaluate sleep and well-being.

RESULTS

At the end of the treatment period, premenopausal women receiving EPT had more awakenings from stage 1 sleep (p = 0.047) and postmenopausal women with EPT had a greater total number of awakenings (p = 0.031) than the corresponding placebo group. Further, sleepiness decreased less in the premenopausal EPT group than in the placebo group (p = 0.031). In postmenopausal women, EPT decreased and placebo slightly increased slow wave activity during the second non-rapid eye movement sleep episode (p = 0.046).

CONCLUSIONS

In premenopausal and late postmenopausal women, EPT had only random and marginal effects on sleep. Although the limited findings were mostly unfavorable for EPT, one cannot conclude that EPT deteriorates sleep. Further, neither middle-aged cycling premenopausal women nor older postmenopausal women benefit from estrogen-progestin treatment in terms of their sleep quality.

Fiber connections between the cerebral cortex and the corpus callosum in Alzheimer's disease: a diffusion tensor imaging and voxel-based morphometry study

Regional cortical atrophy in Alzheimer's disease (AD) most likely reflects the loss of cortical neurons. Several diffusion tensor imaging studies reported reduced fractional anisotropy (FA) in the corpus callosum in AD. The aim of this study was to investigate the association between reduced FA in the corpus callosum and gray matter atrophy in AD. Thirteen patients with AD with a mean (+/-standard deviation) age of 68.3 years (+/-11.5) and mean Mini Mental State Examination (MMSE) score of 21.8 (+/-4.8) were recruited. There were 13 control subjects with a mean age of 66.7 years (+/-6.4) and MMSE of 29.1 (+/-0.7). We used voxel-based morphometry of gray matter maps and region of interest-based analysis of FA in the corpus callosum. FA values of the anterior corpus callosum in AD patients were significantly correlated with gray matter volume in the prefrontal cortex and left parietal lobes. FA values of the posterior corpus callosum were significantly correlated with gray matter volume in the bilateral frontal, temporal, right parietal, and occipital lobes. In control subjects, no correlations were detected. Our findings suggest that decline of FA in the corpus callosum may be related to neuronal degeneration in corresponding cortical areas.

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.

Relationship between climacteric symptoms and serum galanin levels in post-menopausal women

OBJECTIVES

The aim of the study was to evaluate the possible relationship between climacteric symptoms and serum galanin concentrations in post-menopausal women.

MATERIALS AND METHODS

We studied 38 women who attended the Department of Gynecological Endocrinology in Poznan because of climacteric complaints. The control group comprised 16 women [mean age 22.2 yr (SD+/-0.9 yr), range 18-24 yr] who were menstruating regularly and had normal body mass index. We evaluated the severity of climacteric symptoms using the Kupperman scale and we measured 17beta-estradiol, FSH and galanin serum concentrations by radioimmunoassay.

RESULTS

The mean serum galanin concentration was 18.7 pg/ml (SD+/-16.1 pg/ml) in the study group and 21.9 pg/ml (SD+/-9.4 pg/ml) in the control group. The difference was not statistically relevant. The mean serum galanin concentration was 15.9 pg/ml (SD+/-12.6 pg/ml) in the group of patients with mild and moderate climacteric symptoms and 29.5 pg/ml (SD+/-23.3 pg/ml) in the group of patients with severe climacteric symptoms. The difference between the two groups was statistically significant (Student t-test: p<0.05). Climacteric patients with nervousness had lower serum galanin concentration than patients without this symptom (Student t-test: p<0.05).

CONCLUSIONS

a) Serum galanin concentration in post-menopausal women is related to severity of climacteric syndrome; b) the presence of nervousness in post-menopausal women is related to lower serum galanin level.

Electroencephalographic sleep profiles in treatment course and long-term outcome of major depression: association with DEX/CRH-test response

Altered electroencephalographic (EEG) sleep patterns are among the most prominent neurobiological findings in depression. Several of these alterations have been suggested to be associated with an unfavorable long-term outcome. However, the impact of pathological sleep parameters on a more recurrent course of illness or vice versa still warrants clarification. Underlying mechanisms may involve systems known to be related to both sleep regulation and long-term course of depression such as the hypothalamic-pituitary-adrenocortical (HPA) axis. Thus, EEG sleep profiles of patients with depression were examined to determine whether (1) the retrospective clinical course of depression, and (2) the prospective long-term outcome in follow-up are associated with EEG sleep parameters. To elucidate related mechanisms HPA system functioning was evaluated by using the combined DEX/CRH test. Fifteen patients with affective disorders who participated in an earlier controlled antidepressant treatment study over 6 weeks were consecutively enrolled in an exploratory follow-up study. The retrospective analysis revealed that during the acute state of depression predominantly sleep continuity measures were associated with the number of previously experienced episodes. While this relation disappeared during treatment and did not correlate with the prospective course, decreased slow wave sleep variables especially in the first sleep period and increased rapid eye movement density were predictive for the occurrence of recurrences in follow-up and, hence, probably reflect more trait-like markers. Additionally, EEG sleep variables unfavorable for long-term outcome were related to excessive stress hormone response in the DEX/CRH-test. These disturbances may reflect important mechanisms responsible of causing and maintaining the disease process of depression.

Alterations in EEG activity and sleep after influenza viral infection in GHRH receptor-deficient mice

Viral infections induce excess non-rapid eye movement sleep (NREMS) in mice. Growth hormone-releasing hormone receptor (GHRH receptor) was previously identified as a candidate gene responsible for NREMS responses to influenza challenge in mice. The dwarf lit/lit mouse with a nonfunctional GHRH receptor was used to assess the role of the GHRH receptor in viral-induced NREMS. After influenza A virus infection the duration and intensity [electroencephalogram (EEG) delta power] of NREMS increased in heterozygous mice with the normal phenotype, whereas NREMS and EEG delta power decreased in homozygous lit/lit mice. Lit/lit mice developed a pathological state with EEG slow waves and enhanced muscle tone. Other influenza-induced responses (decreases in rapid eye movement sleep, changes in the EEG high-frequency bands during the various stages of vigilance, hypothermia, and decreased motor activity) did not differ between the heterozygous and lit/lit mice. GH replacement failed to normalize the NREMS responses in the lit/lit mice after influenza inoculation. Decreases in NREMS paralleled hypothermia in the lit/lit mice. Lung virus levels were similar in the two mouse strains. Lit/lit mice had a higher death rate after influenza challenge than the heterozygotes. In conclusion, GHRH signaling is involved in the NREMS response to influenza infection.

Effect of sleep and sleep deprivation on serotonergic neurotransmission in the hippocampus: a combined in vivo microdialysis/EEG study in rats

Brainstem serotonergic neurotransmission is implicated in sleep regulation. However, the role of serotonin (5-HT) in forebrain regions in sleep-wake mechanisms is still unclear. Here, we have investigated, using a combined in vivo microdialysis/electroencephalogram method, the relationship between hippocampal 5-HT levels and sleep-wake behaviour in the rat. A clear-cut relationship was found between hippocampal 5-HT levels and vigilance state. The highest levels of 5-HT were observed during wakefulness, whereas a progressive decrease of 5-HT going from nonrapid eye movement sleep to rapid eye movement sleep was found. Sleep deprivation (SD) causes a transient enhancement of mood in depressed patients. Given the putative role of 5-HT in the aetiology of depression and the therapeutical efficacy of selective serotonin reuptake inhibitors in this illness, we also studied hippocampal 5-HT during 4 h of SD and during the subsequent recovery period. During the whole SD period, 5-HT levels were elevated substantially when compared to 5-HT levels during basal wakefulness. However, no changes in 5-HT levels and the relationship between hippocampal 5-HT and vigilance state were found during the subsequent recovery period. As SD is a potentially stressful experience and glucocorticoids are involved in the regulation of serotonergic neurotransmission and sleep, we investigated the effects of SD on free corticosterone levels. SD caused a marked rise in free corticosterone levels. However, the effects of SD on 5-HT seem not to be mediated by this hormone, because adrenalectomy did not affect the rise in hippocampal 5-HT during SD. We hypothesize that the elevated hippocampal 5-HT levels during SD may participate in the transient mood enhancing properties of forced wakefulness observed in depressed patients.

The alerting effects of dexamethasone

The purpose of this study was to characterize the level of sleepiness/alertness following the nocturnal administration of dexamethasone. Thirteen healthy men participated in this study. Following the initial screening, dexamethasone (4 mg) or placebo was administered at 22:30 hr in a randomized double-blind procedure. Subjects were given nap opportunities at 23:00, 1:00, 3:00, 4:30, 5:30, 7:30, 9:30, 11:30, 13:30, 15:30, 17:30, and 19:30 hr. The administration of dexamethasone resulted in an overall lengthening of sleep latency. Although the two groups displayed comparable latencies to stage 1 for the 23:00-7:30 hr nap opportunities, the administration of dexamethasone resulted in significantly longer latencies on the 9:30-19:30 hr nap opportunities. Consistent with these results, participants reported significantly greater levels of alertness on the Stanford Sleepiness Scale. The results of this study revealed greater levels of daytime alertness following the nocturnal administration of dexamethasone.

Neuropeptides: general characteristics and neuropharmaceutical potential in treating CNS disorders

The general characteristics of neuropeptides are discussed as a background for the understanding of their role in regulation of physiological systems. The extent of those systems that are crucially affected by neuropeptides is vast and the complexity of their interactions makes the clinical focus on a specific neuropeptide unsatisfactory. The clinical potential of neuropeptides affecting eating disorders, CNS behavioral disorders and the neuroregenerative and neuroprotective action of neuropeptides is discussed. It is probable that successful neuropeptide therapeutics will depend upon the application of translational and combinational research using various ingenious combinations of neuropeptides, their agonists and antagonists, neuropeptide receptor agonists and antagonists, improved methods of delivery and the development of peptides targeted to the genetic profile of individual patients.

Hormones and breathing

A number of hormones, including hypothalamic neuropeptides acting as neurotransmitters and neuromodulators in the CNS, are involved in the physiologic regulation of breathing and participate in adjustment of breathing in disease. In addition to central effects, some hormones also control breathing at peripheral chemoreceptors or have local effects on the lungs and airways. Estrogen and progesterone seem to protect from sleep-disordered breathing, whereas testosterone may predispose to it. Progesterone and thyroxine have long been known to stimulate respiration. More recently, several hormones such as corticotropin-releasing hormone and leptin have been suggested to act as respiratory stimulants. Somatostatin, dopamine, and neuropeptide Y have a depressing effect on breathing. Animal models and experimental human studies suggest that also many other hormones may be involved in respiratory control.

Functional continuum of regulatory peptides (RPs): vector model of RP-effects representation

During the past decades, bioactive (regulatory) peptides have been identified as the major players in the regulation of many important biological processes. Dozens of peptides have found their application as pharmaceutical agents, which further stimulated research in this field making it one of the most rapidly developing areas on the edge of biological science and medicine. However, the fast accumulation of enormous amounts of experimental data has revealed a great difficulty in their analysis and demanded the development of a systematic approach for generalization of the obtained information. We propose a new computer-based algorithm for studying biological activities of regulatory peptides and their groups based on their representation as vectors in n -dimensional functional space. Our method allows the rapid analysis of databases containing thousands of polyfunctional regulatory peptides with overlapping spectra of physiological activity. The described method permits to perform several types of correlations which, when applied to the large databases, could reveal new important information about the system of regulatory peptides. It can select the groups of peptides with similar physiological role (peptide constellations) and search for the optimal peptide combinations with predetermined spectrum of effects and minimal side effects for their further pharmacological application. It can also reveal the role of regulatory peptides in induction of chain physiological reactions.

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.

Sleep and the hypothalamo-pituitary-adrenocortical system

The intention of this review is to summarize the current knowledge on the bidirectional interaction between sleep EEG and the secretion of corticotropin (ACTH) and cortisol. The administration of various hypothalamic-pituitary- adrenocortical (HPA) hormones and their antagonists exerts specific sleep-EEG changes in several species including humans. It is well documented that corticotropin releasing hormone (CRH) impairs sleep and enhances vigilance. In addition, it may promote REM sleep. Changes in the growth hormone-releasing hormone (GHRH):CRH ratio in favour of CRH appear to contribute to shallow sleep, elevated cortisol levels and blunted GH in depression and ageing. On the other hand, in women GHRH appears to exert CRH-like effects on sleep. Acute cortisol administration increases slow-wave sleep (SWS) and GH, probably due to feedback inhibition of CRH, and inhibits REM sleep. With the mixed glucocorticoid and progesterone receptor antagonist mifepriston sleep is disrupted. Subchronic administration of the glucocorticoid agonist methylprednisolone desinhibited REM sleep. A synergism of elevated CRH and cortisol activity may contribute to REM disinhibition during depression. Also ACTH and vasopressin modulate sleep specifically but their physiological role remains unclear. For example acute icv vasopressin enhances wakefulness in rats, whereas its long-term administration increases SWS in the elderly. In various studies the interaction of sleep EEG and HPA hormones has been investigated at the baseline, after manipulation of sleep-wake behaviour and after environmental changes. Most studies agree that the circadian pattern of cortisol is relatively independent from sleep and environmental influences. Some data suggest a major effect of light on cortisol secretion. Sleeping is widely associated with blunting and awakenings are linked with increases of HPA hormones.

Neurosteroids and behavior

Neurosteroid production may be a mechanism to counteract the negative effects of stress and return organisms toward homeostasis. Stress induces an increase in neurosteroid production. Neurosteroids affect two of the most widely distributed neurotransmitter and receptor systems in the central nervous system (CNS): gamma-aminobutyric acid (GABA) and glutamate. This ability of this class of compounds to affect both the primary excitatory and the inhibitory systems in the CNS allows the modulation of a wide array of behaviors. For example, neurosteroids modulate anxiety, cognition, sleep, ingestion, aggression, and reinforcement. In general, neurosteroids that are positive modulators of N-methyl-D-aspartate receptors enhance cognitive performance and decrease appetite. Neurosteroids that are positive modulators of GABAA receptors decrease anxiety, increase feeding and sleeping, and exhibit a bimodal effect on aggression that may be secondary to effects on anxiety and cognition. Some data suggest that neurosteroids have reinforcing effects, which could affect their clinical utility. Drug discrimination studies are helping scientists to dissect more closely the receptor systems affected by neurosteroids at the behavioral level.

Sleep, the hypothalamic-pituitary-adrenal axis, and cytokines: multiple interactions and disturbances in sleep disorders

Sleep is an important component of mammalian homeostasis, vital for survival. Sleep disorders are common in the general population and are associated with significant medical, psychologic, and social disturbances. Sleep, in particular deep sleep, has an inhibitory influence on the HPA axis, whereas activation of the HPA axis or administration of glucocorticoids can lead to arousal and sleeplessness. Insomnia, the most common sleep disorder, is associated with a 24-hour increase of ACTH and cortisol secretion, consistent with a disorder of central nervous system hyperarousal. Sleepiness and fatigue are very prevalent in the general population, and recent studies have demonstrated that the proinflammatory cytokines IL-6 and/or TNF-alpha are elevated in disorders associated with excessive daytime sleepiness, such as sleep apnea, narcolepsy, and idiopathic hypersomnia. Sleep deprivation leads to sleepiness and daytime hypersecretion of IL-6. Combined, these findings suggest that the HPA axis stimulates arousal, while IL-6 and TNF-alpha are possible mediators of excessive daytime sleepiness in humans.

Effects of clozapine on sleep measures and sleep-associated changes in growth hormone and cortisol in patients with schizophrenia

There have been limited reports on the effect of the atypical anti-psychotic agent clozapine on sleep measures and hormone secretion. The goal of this study was to determine the type, rate, and extent of changes in sleep measures and nighttime secretion of growth hormone (GH) and cortisol during clozapine treatment. Five schizophrenic patients (age: 32.4+/-7.4) and five age- and sex-matched normal subjects (age: 33.0+/-5.1) underwent nocturnal polysomnography (NPSG) before clozapine therapy (S1), and during early and late clozapine therapy (S2 and S3). Serum GH and cortisol levels were monitored during each NPSG. NPSG findings showed that the mean total sleep time, sleep efficiency, and duration of awakening were increased at S2, and maintained until S3. The mean amounts of stage 2 sleep at S2 and S3 increased significantly compared with that of S1. In unmedicated schizophrenic patients, the mean plasma GH level in rapid eye movement sleep was lower than during the waking stage, and the mean level of plasma cortisol was higher during the waking stage. Plasma cortisol levels did not differ between control subjects and patients at any time, but clozapine treatment decreased plasma cortisol levels at S2 compared with S1 and S3. Plasma GH levels were unchanged by clozapine treatment. Clozapine improved sleep continuity and increased stage 2 sleep time from the beginning of therapy. These effects were maintained through at least 7 weeks of therapy. However, clozapine did not affect the relationship of plasma GH and cortisol levels with sleep stages in schizophrenic patients.

To eat or to sleep? Orexin in the regulation of feeding and wakefulness

Orexin-A and orexin-B are neuropeptides originally identified as endogenous ligands for two orphan G-protein-coupled receptors. Orexin neuropeptides (also known as hypocretins) are produced by a small group of neurons in the lateral hypothalamic and perifornical areas, a region classically implicated in the control of mammalian feeding behavior. Orexin neurons project throughout the central nervous system (CNS) to nuclei known to be important in the control of feeding, sleep-wakefulness, neuroendocrine homeostasis, and autonomic regulation. orexin mRNA expression is upregulated by fasting and insulin-induced hypoglycemia. C-fos expression in orexin neurons, an indicator of neuronal activation, is positively correlated with wakefulness and negatively correlated with rapid eye movement (REM) and non-REM sleep states. Intracerebroventricular administration of orexins has been shown to significantly increase food consumption, wakefulness, and locomotor activity in rodent models. Conversely, an orexin receptor antagonist inhibits food consumption. Targeted disruption of the orexin gene in mice produces a syndrome remarkably similar to human and canine narcolepsy, a sleep disorder characterized by excessive daytime sleepiness, cataplexy, and other pathological manifestations of the intrusion of REM sleep-related features into wakefulness. Furthermore, orexin knockout mice are hypophagic compared with weight and age-matched littermates, suggesting a role in modulating energy metabolism. These findings suggest that the orexin neuropeptide system plays a significant role in feeding and sleep-wakefulness regulation, possibly by coordinating the complex behavioral and physiologic responses of these complementary homeostatic functions.

Non-linear changes of electrocortical activity after antenatal betamethasone treatment in fetal sheep

We determined the effects of betamethasone on the fetal sheep electrocorticogram (ECoG) using linear (power spectral) and non-linear analysis. For non-linear analysis we used an algorithm based on the Wolf algorithm for the estimation of the leading Lyapunov exponent which calculates a prediction error based on the course of the time series in the phase space. A high prediction error stands for low predictibility or low regularity and vice versa. After 48 h of baseline recordings, vehicle (n = 6) or betamethasone (n = 7) at 10 microg h(-1) was infused over 48 h to the sheep fetus at 128 days gestational age (0.87 of gestation). ECoG spectral analysis revealed no difference in power spectrum between vehicle- and betamethasone-treated fetuses. The prediction error of the ECoG during REM sleep was higher than during non-REM or quiet sleep in both groups (P < 0.0001) revealing lower causality of brain activity during REM sleep. During REM sleep, prediction error significantly decreased 18-24 h after onset of betamethasone treatment (P < 0.05) and returned to baseline values within the following 24 h of continued betamethasone treatment. No ECoG changes were found during quiet sleep. Non-linear ECoG changes during metabolically active REM sleep accompanied the previously described decrease in cerebral blood flow. These results suggest that betamethasone in doses used in perinatal medicine acutely alters complex neuronal activity.

Granulocyte-macrophage colony-stimulating factor modulates rapid eye movement (REM) sleep and non-REM sleep in rats

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a hematopoietic cytokine that may affect various functions of the CNS because the molecule and its receptors are expressed in the brain. The present study examines the effects of GM-CSF on sleep using rats and the secretion of three neurotransmitters/hormones that are involved in sleep regulation. When infused intracerebroventricularly at doses as low as 10 pmol for 10 hr during the dark period, GM-CSF promoted predominantly rapid eye movement (REM) sleep and moderate amounts of non-REM sleep without eliciting fever. An injection of GM-CSF (3.0 pmol) into the arcuate nucleus increased the release of nitric oxide (NO) from the hypothalamus but did not alter plasma levels of growth hormone. The release of somatostatin (SRIF) from the medial basal hypothalamus was stimulated by 1 x 10(-)(11) M GM-CSF. These findings indicated that centrally administered GM-CSF stimulates SRIF release through activation of the NO system in the hypothalamus. Because SRIF promotes REM sleep, it may also mediate the effects of GM-CSF on REM sleep. The present study indicates a novel central effect of GM-CSF that modulates sleep, supporting the notion that hematopoietic cytokines also play roles in the CNS.

Prenatal stress is associated with depression-related electroencephalographic sleep changes in adult male rats: a preliminary report

1. Prenatal stress in rats has been shown to produce long-term behavioral, neuroendocrine and neurochemical changes. These changes may model aspects of human depressive illness. 2. In this pilot investigation, adult male offspring exposed to stress in utero and non-stressed controls were studied using 24-hour electroencephalographic sleep recordings. 3. Prenatally stressed animals demonstrated reduced latency to the onset of rapid eye movement (REM) sleep, prolongation of the first REM episode, and diminished slow-wave sleep. 4. Although preliminary, the observed changes parallel those seen in studies of human depression. These data further support the face validity of the prenatal stress model as a potential tool for future studies on the pathophysiology of depressive disorder.