Hyperthyroidism, sleep and growth hormone

Nongenomic roles of thyroid hormones and their derivatives in adult brain: are these compounds putative neurotransmitters?

We review the evidence regarding the nongenomic (or non-canonical) actions of thyroid hormones (thyronines) and their derivatives (including thyronamines and thyroacetic acids) in the adult brain. The paper seeks to evaluate these compounds for consideration as candidate neurotransmitters. Neurotransmitters are defined by their (a) presence in the neural tissue, (b) release from neural tissue or cell, (c) binding to high-affinity and saturable recognition sites, (d) triggering of a specific effector mechanism and (e) inactivation mechanism. Thyronines and thyronamines are concentrated in brain tissue and show distinctive patterns of distribution within the brain. Nerve terminals accumulate a large amount of thyroid hormones in mature brain, suggesting a synaptic function. However, surprisingly little is known about the potential release of thyroid hormones at synapses. There are specific binding sites for thyroid hormones in nerve-terminal fractions (synaptosomes). A notable cell-membrane binding site for thyroid hormones is integrin αvβ3. Furthermore, thyronines bind specifically to other defined neurotransmitter receptors, including GABAergic, catecholaminergic, glutamatergic, serotonergic and cholinergic systems. Here, the thyronines tend to bind to sites other than the primary sites and have allosteric effects. Thyronamines also bind to specific membrane receptors, including the trace amine associated receptors (TAARs), especially TAAR1. The thyronines and thyronamines activate specific effector mechanisms that are short in latency and often occur in subcellular fractions lacking nuclei, suggesting nongenomic actions. Some of the effector mechanisms for thyronines include effects on protein phosphorylation, Na+/K+ ATPase, and behavioral measures such as sleep regulation and measures of memory retention. Thyronamines promptly regulate body temperature. Lastly, there are numerous inactivation mechanisms for the hormones, including decarboxylation, deiodination, oxidative deamination, glucuronidation, sulfation and acetylation. Therefore, at the current state of the research field, thyroid hormones and their derivatives satisfy most, but not all, of the criteria for definition as neurotransmitters.

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.

Effects of acute microinjections of thyroid hormone to the preoptic region of hypothyroid adult male rats on sleep, motor activity and body temperature

Thyroid hormones induce short-latency nongenomic effects in adult brain tissue, suggesting that their acute administration would affect brain activity in intact animals. The influence on EEG-defined sleep of acute restoration of l-3,3'5-triiodothyronine (T3) to a sleep-regulatory brain region, the preoptic region, was examined in hypothyroid rats. Sleep parameters were monitored for 48 h weekly: for 24 h immediately following a control microinjection and for an additional 24h after a second microinjection including a T3 dose to the preoptic region or lateral ventricle. Male albino rats were implanted with EEG and EMG electrodes, abdominal temperature/activity transponders and unilateral lateral ventricle cannulae or bilateral preoptic region cannulae, and were given 0.02% n-propythiouracil (PTU) in their drinking water for 4 weeks. For histologically-confirmed bilateral preoptic region cannula placements (N=7), effects of T3 (especially a 3 μg dose) were apparent within 10h of injection as decreases in REM, NREM and total sleep and increases in waking and activity. Minimal effects of lateral ventricle T3 microinjection were demonstrated (N=5). Significant effects due to the time of day on the experimental measures were seen in both lateral ventricle and preoptic region groups, but these effects did not interact with the effect of administered hormone dose. These effects of T3 microinjection to the preoptic region were demonstrated after acute injections and within hours of injection rather than after chronic administration over days.

Effects of acute microinjections of thyroid hormone to the preoptic region of euthyroid adult male rats on sleep and motor activity

In adult brain tissue, thyroid hormones are known to have multiple effects which are not mediated by chronic influences of the hormones on heterodimeric thyroid hormone nuclear receptors. Previous work has shown that acute microinjections of l-triiodothyronine (T3) to the preoptic region significantly influence EEG-defined sleep in hypothyroid rats. The current study examined the effects of similar microinjections in euthyroid rats. In 7 rats with histologically confirmed microinjection sites bilaterally placed in the preoptic region, slow-wave sleep time was significantly decreased, but REM and waking were increased as compared to vehicle-injected controls. The EEG-defined parameters were significantly influenced by the microinjections in a biphasic dose-response relationship; the lowest (0.3μg) and highest (10μg) doses tested were without significant effect while intermediate doses (1 and 3μg) induced significant differences from controls. There were significant diurnal variations in the measures, yet no significant interactions between the effect of hormone and time of day were demonstrated. Core body temperature was not significantly altered in the current study. The demonstration of effects of T3 within hours instead of days is consistent with a rapid mechanism of action such as a direct influence on neurotransmission. Since the T3-mediated effects were robust in the current work, euthyroid rats retain thyroid hormone sensitivity which would be needed if sleep-regulatory mechanisms in the preoptic region are continuously modulated by the hormones. This article is part of a Special Issue entitled LInked: BRES-D-12-01552 & BRES-D-12-01363R2.

Hyperthyroidism differentially regulates neuropeptide S system in the rat brain

Thyroid hormones play an important role in the regulation of energy balance, sleep and emotional behaviors. Neuropeptide S (NPS) is a recently discovered neuropeptide, regulating feeding, sleep and anxiety. Here, we examined the effect of hyperthyroidism on the gene and protein expression of neuropeptide S and its receptor (NPS-R) in the hypothalamus, brainstem and amygdala of rats. Our results showed that the expression of NPS and NPS-R was differentially modulated by hyperthyroidism in the rat brain. NPS and NPS-R mRNA and protein levels were decreased in the hypothalamus of hyperthyroid rats. Conversely NPS-R expression was highly increased in the brainstem and NPS and NPS-R expression were unchanged in the amygdala of these rats. These data suggest that changes in anxiety and food intake patterns observed in hyperthyroidism could be associated with changes in the expression of NPS and NPS-R. Thus, the NPS/NPS-R system may be involved in several hyperthyroidism-associated comorbidities.

Effects of supraphysiological doses of levothyroxine on sleep in healthy subjects: a prospective polysomnography study

Disrupted sleep is prevalent in both mood and thyroid disorders. Given the emerging use of thyroid hormones in the treatment of mood disorders, we investigated the effects of supraphysiological doses of levothyroxine (L-T4) on sleep. In an open-label design, 13 healthy subjects received up to 500 μg/day for an eight-week period. A baseline night was polysomnographically recorded (PSG) followed by PSG under the maximum tolerated dose of L-T4. All subjects developed hyperthyroxinemia. The heart rate and respiration rate increased significantly with treatment; a significant increase in body temperature was observed in men but not in women. Surprisingly, treatment with supraphysiological doses of L-T4 did not cause significant effects on sleep architecture. However, the increase in body movements and REM density was close to reaching statistical significance. Here, we report on the sleep data, thyroid hormone levels, and physiological parameters during sleep. We conclude that experimentally induced hyperthyroidism does not profoundly change the sleep structure in healthy individuals underlining the good tolerability of treatment with supraphysiological doses of L-T4 in patients with mood disorders.

Sleep deprivation and energy metabolism: to sleep, perchance to eat?

PURPOSE OF REVIEW

Many people currently sleep only 5-6 h per night. Epidemiological studies have demonstrated that self-reported short sleep is associated with an increased incidence of obesity and diabetes, highlighting the importance of this trend for public health. This finding has triggered renewed research into the mechanisms that link the regulation of mammalian sleep and metabolism.

RECENT FINDINGS

In rodents, periods of starvation are accompanied by increased vigilance and sleep loss, presumably to help maximize food finding and energetic survival, whereas sleep deprivation results in increased energy expenditure and weight loss, consistent with a role of sleep in energy conservation and tissue maintenance. Information about the corresponding processes in humans is limited. Available data indicate that despite the presence of qualitative and quantitative differences, human sleep and metabolism also share reciprocal connections.

SUMMARY

Evolution in an environment with limited resources has established bidirectional links between sleep and energy homeostasis, the molecular mechanisms of which are emerging rapidly. Epidemiological data suggest that the unique ability of humans to restrict their sleep voluntarily in an environment that promotes physical inactivity and overeating may have a negative impact on metabolic health. Randomized intervention trials are needed to confirm the validity of this hypothesis.

Prepro-orexin mRNA levels in the rat hypothalamus, and orexin receptors mRNA levels in the rat hypothalamus and adrenal gland are not influenced by the thyroid status

Orexins are two recently discovered neuropeptides that play an important role in the regulation of food intake and in the regulation of the sleep-wake cycle. In this work we examined the effects of thyroid hormones on prepro-OX expression in the rat hypothalamus, and OXRs expression in the rat hypothalamus and adrenal gland. Hypo- and hyperthyroidism were induced in adult male rats, and the levels of hypothalamic prepro-OX and OXRs mRNA, and adrenal OXRs mRNA were determined using semiquantitative reverse transcription-polymerase chain reaction and/or in situ hybridization. Our results indicate that thyroid status affects neither prepro-OX in the hypothalamus nor hypothalamic and adrenal gland OXRs expression.

Individual variations in the sleep of depression

Variations in the intensity or severity of affective disorders were evaluated relative to perturbations in nocturnal sleep physiology. Individual variations in polygraphic features of the sleep cycle based upon psychopathologic scale ratings were investigated in two constituencies (Ns = 6) for 8 hr during 1-3 consecutive nights. The constituencies consisted of twelve young adult (18-25 years) nonpsychotic unipolar depressed psychiatric patients with a primary affective illness and an age-matched normal healthy control group (N = 8). The severely versus mildly depressed patient subgroups scored significantly higher on the Hamilton, Beck and Zung psychopathologic rating scales, indicating a larger magnitude of depressive symptomatology. The average value for total time asleep was 6.1 hr in severely versus 7.8 hr among the mildly depressed patients and controls. EEG-sleep of the severely versus mildly depressed patients and controls contained significantly less stages 2 and 3. Although total time asleep was almost identical in the mildly depressed constituency compared with controls, patients accumulated significantly more of stages 2 and 3. Both patient subgroups exhibited a significantly shorter REM latency than controls. REM latency was reduced to a significantly lower level in the severely versus mildly depressed patients. A significant decrease of REM cycle duration occurred in the polygraphic sleep recordings of severely depressed patients compared with the age-matched controls. The shortened REM latencies indicate a disinhibition of neural processes that would normally delay appearance of the initial REM episodes during nocturnal sleep. The present study generally extends and confirms finding on nocturnal EEG-sleep disturbances in depression associated with the severity of affective illness, particularly the disrupted REM cycle and shorter REM latency.

Are poor sleepers changed into good sleepers by hypnotic drugs?

Sleep can be measured by subjective ratings, electrophysiological recordings and by the physiological and biochemical changes occurring with sleep. Using these methods, we can select those who rate their sleep as unsatisfactory and those who feel fully satisfied by their sleep. Electrophysiological recordings of sleep show that there are relatively small differences between these good and poor sleepers: poor sleepers sleep less than good sleepers, but not as little as they think. However, the complaints of poor sleepers that they feel unrestored by their sleep should not be dismissed, for investigations employing the tools of physiology and biochemistry have revealed differences between good and poor sleepers that suggest that the sleep of poor sleepers may indeed be less restorative. The actions of hypnotic drugs on sleep can be similarly investigated. Preliminary findings suggest that hypnotic drugs may reverse some of the detrimental metabolic concomitants of poor sleep.

Pituitary secretions and wake-sleep cycle

Neurohumoral correlations of sleep are considered from three aspects: 1. Metabolism and cerebral blood circulation (CBF, EEG, endocranial pressure, cerebral temperature); 2. Neuromediators and neuropeptides (5-HT, hypnogen neuropeptides); 3. The influence of the sleeping-waking cycle on adeno-hypophyseal secretion rhythms (GH, PRL, LH, TSH). Variations of these parameters can play an important role in the onset of night crises of migraine and cluster headache.

Correlations of some physical variables with REM sleep and slow wave sleep in man

Polysomnographic recordings were taken on 11 healthy male students aged 19-23 years. The correlations were examined between the various physical variables and the appearance rates of REM sleep and slow wave sleep (SWS). The height showed a significant inverse correlation with %st.4 sleep and with %SWS and the plantar length with %SWS. The body weight and chest circumference showed a significant inverse correlation with %REM sleep. The weight/height ratio tended toward an inverse correlation with %REM sleep. Both the body surface area and basal metabolic rate showed a significant inverse correlation with %st.4 and %REM sleep. There was no significant correlation between the total sleep time and each physical variable. From these results the roles of REM sleep and slow wave sleep in man were discussed.

Sleep pattern variations as a function of age in affective disorders

Polygraphic features of nocturnal sleep were evaluated in young adult psychiatric patients during acute unipolar depressive episodes. Averaged values and variability of polygraphic indexes were examined in 12 depressed patients under the age of 26 individually matched with a normal control group. Sleep was polygraphically recorded in the Laboratory for three consecutive nights from 12-8.00 a.m. Although average total time asleep was approximately equivalent (greater than 7.3 hr) between groups, depressives accumulated significantly: (i) less stage 4, (ii) more stage 1, (iii) vascillations among sleep stages, but (iv) most especially increased transitions into stage 1 and (v) intermittent wakefulness. The recorded sleep perturbations in young depressives were extremely variable across nights and among individuals. This was especially conspicuous across nights as reflected by significantly larger variability (SD) for: (i) transitions into stage 1, (ii) intermittent wakefulness and (iii) epsilon accumulations of stage 2. Variability (the SD) between individuals was also more substantial for: (i) total time asleep, (ii) stage 1, (iii) intermittent wakefulness, (iv) epsilon stage shifts and (v) intrusions into stage 1. The polygraphic recordings of young depressives contained anomalies reported for clinical pathologic states accompanied by physiological disregulation such as hypersomnia, narcolepsy and schizoaffective disorders. Polygraphic indexes reflecting the capacity (i) to remain asleep (means +/- SDs) and (ii) accumulate continuous sleep (SDs) indicated an imbalance of the 24-hr rest (sleep)--activity (waking) cycle was present in this constituency concomitant with affective distress. A comparison with selected cross-sectional polygraphic studies revealed that sleep cycle aberrations in young adult depressives were less intense than those which become exacerbated as a function of advanced age. By contrast to prepubertal children or postadolescent young adults who are depressed, elderly accumulate: (i) lower total sleep times, (ii) less proportions of stages 3-4 and (iii) remain awake longer. It is concluded that sleep-polygraphic anomalies in postadolescent depression are an attenuated form of the REM-NREM cycle perturabation endemic to affective disease occurring with advanced age or senescence.

Sleep related breathing disorders in older men: a search for underlying mechanisms

The incidence of sleep-related breathing disorders (SRBDs) associated with hemoglobin desaturation was determined by nocturnal polygraphic evaluations in 26 healthy men, aged 55-70 years. Sixteen subjects (62%) had abnormal rates of at least 12 episodes per hour of sleep: 8 had occlusive, and 8 had central apnea or hypopnea. During waking ten of 16 SRBD subjects and only one subject without SRBDs exhibited either an elevated nasopharyngeal airway resistance (n = 4) or a reduced ventilatory response to hypercapnia (n = 4) and/or hypoxia (n = 3). However, these abnormalities were not related to the type or severity of SRBDs, and 6 subjects with SRBDs demonstrated no respiratory defect. We conclude that SRBDs have a very high incidence in older males and are not usually secondary to pulmonary cardiac, neurological, or behavioral disorders. Additionally, we hypothesize that abnormalities in ventilatory control or upper airway resistance contribute to SRBDs, but depression of brain stem reticular formation activity during sleep plays a primary role in these disorders. Factors related to both aging and SRBDs are reviewed. These include reduced chemoreceptor responses, altered steroid hormone metabolism, and use and metabolism of hypnotic drugs and alcohol.

Polysomnographic effects of thyroid hormones primary myxedema

Nine primary myxedematous patients were subjected to all-night polysomnographic recordings under the following conditions: (1) basal or myxedematous state; (2) acute replacement therapy (treatment with thyroid hormones at doses that increased weekly to the maximal replacement dose, Mrd); and (3) chronic replacement therapy (maintenance on the Mrd; euthyroid state). The most striking abnormality found in the sleep pattern during the myxedematous state was observed in both young adult (greater than 20 years old) and adult (greater than 50 years old) patients, consisting of either a complete absence or very low levels of slow wave sleep (SWS). Replacement therapy was accompanied by a restoration of the normal sleep pattern in 3 of the 4 patients that were followed. In contrast, younger patients (14-18 years old with a bone age of less than or equal to 10 years) had normal levels of SWS, with the exception of an adolescent with a bone age of less than 3 years. The latency for rapid eye movement (REM) sleep tended to increase during acute replacement therapy and became normal when euthyroidism was reached. These results lend support to the proposal that thyroid hormones exert central effects on the adult CNS.

Nocturnal electrographic features of frequently changing-irregular sleep-wakefulness rhythms

Polygraphic characteristics of nocturnal sleep associated with frequently changing-irregular rest-activity schedules were investigated in healthy young adults. Two groups each of 12 male university students were classified according to a priori criteria as either: (a) controls who slept regularly for 7--8 hr at night or (b) whose retiring and arising times combined varied chronically +/- 1.5 hr. Sleep was recorded during three consecutive 8-hr nocturnal periods at fixed clock times. Polygraphic indices generally reflected greater discontinuity and fragmentation associated with the nocturnal sleep in the young adults whose 24-hr rest-activity cycle tended to be frequently changing-irregular. The significantly: (a) larger absolute quantities of (i) transitional stage 1 sleep, (ii) intermittent wakefulness and (b) increases stage shifts provided some indication that the intrasleep cycle becomes disturbed when rest-activity schedules follow no predictable pattern in the everyday environment. Despite, or because of, the enforced hour (11:30 p.m +/- 30 min) for retiring, it is possible that the capacity to fall asleep had become phase-delayed among subjects with irregular rest-activity schedules who experienced more initial wakefulness (on average) before sleep onset stage 1. Finally, the recorded sleep perturbations associated with frequently changing-irregular schedules were extremely variable across nights and among individuals. This was especially pronounced on a nightly basis as reflected by significantly larger variability (SDs): (a) in the latency to sleep onset, for (b) total time asleep, (c) intermittent wakefulness, and (d) the ultradian (90-min) REM cycle. Variability (the SD) between individuals was also more substantial for these same polygraphic measures at statistically significant levels.

A clinical and EEG sleep study in the differential diagnosis of pre-pubertal depression: state of the art

The diagnosis of depression in childhood and adolescence remains problematic. We present an overview of the literature on the diagnosis of childhood and adolescent depression with particular reference to the potential utility of EEG sleep studies. A case of a pre-pubertal boy with depressive symptomatology is presented to illustrate some of the diagnosis difficulties and the application of EEG sleep studies in their resolution. The need for further systematic investigation of EEG sleep correlation of depression in childhood and adolescence is emphasized.

Sleep and body restitution

Although human non-REM sleep is usually with body restitution, such an hypothesis is debatable. This sleep, like REM sleep, may have a beneficial role for the brain. Because man demonstrates relaxed wakefulness, body restitution may not be confined to human sleep. However, for active mammals, sleep may be an enforced immobiliser facilitating this restitution.

Sleep patterns in the intensive care unit and on the ward after acute myocardial infarction

Twelve patients aged 33--70 years (mean 49.5) underwent nightly recordings in the ICU and subsequently on the ward following acute myocardial infarction. Sleep patterns were analyzed according to night after infarct and ICU versus ward environment. Significant differences in nocturnal sleep patterns from matched controls initially after infarction included greater wakefulness, low REM sleep per cent, long REM latency, fewer REM periods, more awakenings, more stage shifts and decreased sleep efficiency. The usual circadian variation in HR was absent, and there was an estimated 8--10 h of unrecorded daytime sleep, which together suggested a quite generalized disruption of biological rhythms. With time, there was loss of daytime sleep, lowered nocturnal wakefulness and increased REM sleep. Slow-wave sleep (sometimes with very long duration delta waves) increased above normal over post-infarction nights 3--9, and sleep was otherwise renormalized by post-infarction night 9. No sudden sleep changes occurred with transfer from ICU to ward. The altered sleep patterns appeared mainly attributable to infarction itself. Twelve nocturnal anginal attacks occurred. Ten began in NREM sleep and two in REM periods without particularly intense phasic activity. Post-infarction nocturnal angina therefore appears to differ in pathogenesis from angina outside this period, which usually occurs in REM sleep. ECG changes could occur during sleep before awakening with pain, and overall decrease in ECG amplitude sometimes accompanied angina. Most attacks (10 of 12) occurred on post-infarction nights 4 and 5, indicating that undetermined that undetermined factors produce a secondary period of heightened risk at that time.

Changes in sleep pattern after sleep deprivation

Total sleep deprivation (TSD) was performed for one night with 11 healthy male students and three-consecutive-recovery night-sleep was recorded. Special attention was paid to the analysis of the individual difference in SWS(min, %) on the baseline and recovery nights. The total sleep time increased on the first recovery night compared to the baseline, but it decreased significantly on the second and third recovery nights. Stage 1(%) decreased significantly on the first and second recovery nights. Stage SWS(min) showed a significant increase on the first recovery night, while SWS(%) increased significantly on the first and second recovery nights. As for Stage REM(%), there was no significant difference between the baseline and the recovery nights. There was a positive correlation between SWS(min) on the baseline and that on the recovery nights. SWS(%) also showed the same results as those obtained with SWS(min). Between SWS(min) in the baseline and the increase rate of SWS(min) on the first recovery night, there was a significant inverse correlation, while there was a tendency to inverse correlation on the second and third recovery nights. As to SWS(%), there was a significant inverse correlation between SWS(%) in the baseline and the increase rate of SWS(%) on the first and third recovery nights.

Sleep in the rat during food deprivation and subsequent restitution of food

Continuous telemetric EEG recordings served to determine the vigilance states of the rat during 2 control days, 80 h of food deprivation and 64 h following restitution of food. The recordings were supplemented by measurements of food intake, water intake and motor activity. The following 3 sleep parameters were not significantly changed by food deprivation: the daily amount of the vigilance states, the light-dark distribution of sleep and waking, and the 10 min paradoxical sleep (PS) cycle. During food deprivation, PS was depressed in the dark phase of the diurnal cycle and increased in the light phase. The sleep parameter that was most affected by food deprivation was the duration of sleep episodes. Episodes of slow-wave sleep (SWS) and PS were shortened only in the dark phase of the deprivation days, whereas total sleep episodes were progressively decreased in both diurnal phases. After restitution of food, the episodes of SWS and total sleep were immediately lengthened and tended to exceed the control level. The duration of feeding episodes and meal size were significantly increased in comparison to pre-deprivation values, whereas feeding frequency was decreased. Long episodes of continuous motor activity occurred during the dark phase of the refeeding period, while a fragmented activity pattern was typical for the deprivation nights. It is proposed that the adjustment of the length of behavioral episodes may constitute an important adaptive mechanism for the rat.

Factor analysis of objective and subjective characteristics of a night's sleep

Factor analysis was performed on objectively measured and subjectively reported characteristics of 46 nights' sleep in four healthy male subjects. The fragmentation of sleep by awakenings during the night, the delay before falling asleep, the total duration of sleep, and the amount of delta-wave sleep formed the bases of four separate factors.