question: Why are some bodily hormones only produced when we sleep?
comment: I think it would be helpful to examine this question as one example of a more general question: Why do bodies produce some hormones under some conditions but not other? And as a follow-up how are they able to do this? The why question is so easy to answer that it's not very illuminating: it's either because natural selection favored organisms that do it this way, or this is the dominant genetic trait and natural selection didn't strongly disfavor it. Over time, organisms that did it this way survived and, either through selection pressure, or through random chance, reproduced more than organisms that didn't do it this way and now many organisms do it this way. Slightly more interesting is the gene-level view of things, which is that natural selection favored organisms that contained genes for doing it this way, or that this is the dominant genetic trait and natural selection didn't strongly disfavor organisms with it. Over time, organisms with these genes survived and, either through selection pressure, or through random chance, reproduced more than organisms without these genes and now these genes have come to dominate the population. The how it the interesting question though. There are a lot of physical and chemical signals telling cells when to do one thing and when to do another. Some hormones may be produced when gravity pulls sideways at the body and turned off when gravity pulls downward. This could be moderated through the flow of liquids that are affected strongly by gravity such as your blood or your stomach contents. Other hormones could be produced when there is no light present because light exposure on your skin or optic nerve inhibits production. Still others may be produced when your overall metabolic rate is low and chemicals produced during the day are not present or have begun to degrade. As you can see, it may not be the case that some hormones that are produced when sleeping are produced because of sleeping. They could be, but there are also likely a large number of other environmental factors that are associated with sleep and trigger production.
passages: The secretion of many hormones is affected by sleep-wake cycles. For example, melatonin, a hormonal timekeeper, is considered a strongly circadian hormone, whose secretion increases at dim light and peaks during nocturnal sleep, diminishing with bright light to the eyes. In some organisms melatonin secretion depends on sleep, but in humans it is independent of sleep and depends only on light level. Of course, in humans as well as other animals, such a hormone may facilitate coordination of sleep onset. Similarly, cortisol and thyroid stimulating hormone (TSH) are strongly circadian and diurnal hormones, mostly independent of sleep. In contrast, other hormones like growth hormone (GH) & prolactin are critically sleep-dependent, and are suppressed in the absence of sleep. GH has maximum increase during SWS while prolactin is secreted early after sleep onset and rises through the night. In some hormones whose secretion is controlled by light level, sleep seems to increase secretion. Almost in all cases, sleep deprivation has detrimental effects. For example, cortisol, which is essential for metabolism (it is so important that animals can die within a week of its deficiency) and affects the ability to withstand noxious stimuli, is increased by waking and during REM sleep. Similarly, TSH increases during nocturnal sleep and decreases with prolonged periods of reduced sleep, but increases during total acute sleep deprivation. 
   Because hormones play a major role in energy balance and metabolism, and sleep plays a critical role in the timing and amplitude of their secretion, sleep has a sizable effect on metabolism. This could explain some of the early theories of sleep function that predicted that sleep has a metabolic regulation role.
  
  Section::::Sleep function.:Memory processing.
   Sleep arousal are active brain processes medicated and associated with specific brain regions. Despite the fact that various stages of sleep are discrete and quantifiable, the exact function of sleep is unknown. Sleep is controlled both by circadian rhythms and the homeostatic drive produced by wakefulness. Circadian rhythms are produced in the suprachiasmatic nucleus by pacemaker cells which contain transcriptional regulation "clock genes" which have been highly conserved throughout evolution.
   BULLET::::- the role of the pineal in the regulation of the circadian rhythm (neither the function nor even the existence of melatonin was yet known);
  
  BULLET::::- discovery of the role of the thymus in the immune system lay many decades in the future; it remained a mystery organ until after the mid-20th century;
  
  BULLET::::- the pituitary and hypothalamus with their many and varied hormones were far from understood, let alone the complexity of their interrelationships.
   The hypothalamus coordinates many hormonal and behavioural circadian rhythms, complex patterns of neuroendocrine outputs, complex homeostatic mechanisms, and important behaviours. The hypothalamus must, therefore, respond to many different signals, some of which generated externally and some internally. Delta wave signalling arising either in the thalamus or in the cortex influences the secretion of releasing hormones; GHRH and prolactin are stimulated whilst TRH is inhibited.
  
  The hypothalamus is responsive to:
  
  BULLET::::- Light: daylength and photoperiod for regulating circadian and seasonal rhythms
  
  BULLET::::- Olfactory stimuli, including pheromones
  
  BULLET::::- Steroids, including gonadal steroids and corticosteroids
   In neonatal life, gonadal steroids influence the development of the neuroendocrine hypothalamus. For instance, they determine the ability of females to exhibit a normal reproductive cycle, and of males and females to display appropriate reproductive behaviors in adult life.
   The circadian clock exerts constant influence on the body, effecting sinusoidal oscillation of body temperature between roughly 36.2 °C and 37.2 °C. The suprachiasmatic nucleus itself shows conspicuous oscillation activity, which intensifies during subjective day (i.e., the part of the rhythm corresponding with daytime, whether accurately or not) and drops to almost nothing during subjective night. The circadian pacemaker in the suprachiasmatic nucleus has a direct neural connection to the pineal gland, which releases the hormone melatonin at night. Cortisol levels typically rise throughout the night, peak in the awakening hours, and diminish during the day. Circadian prolactin secretion begins in the late afternoon, especially in women, and is subsequently augmented by sleep-induced secretion, to peak in the middle of the night. Circadian rhythm exerts some influence on the nighttime secretion of growth hormone.
   Section::::History.
  
  The earliest notion of signal transduction can be traced back to 1855, when Claude Bernard proposed that ductless glands such as the spleen, the thyroid and adrenal glands, were responsible for the release of "internal secretions" with physiological effects. Bernard's "secretions" were later named "hormones" by Ernest Starling in 1905. Together with William Bayliss, Starling had discovered secretin in 1902. Although many other hormones, most notably insulin, were discovered in the following years, the mechanisms remained largely unknown.
   Section::::Physiological changes.:Systems consolidation.:Sleep and systems consolidation.
  
  The mechanism for systems consolidation is unknown, but it has been established that protein synthesis must occur in the cortex, where the hippocampal independent memory is stored, and that sleep is likely to play a role in systems consolidation (Stickgold & Walker, 2005). Many genes are upregulated during sleep, and therefore there is a possibility that protein synthesis is active in sleep-consolidation (Stickgold & Walker, 2005). It remains to be seen if cortical consolidation uses the same mechanisms as the hippocampus to establish the memory trace.
  
  Section::::Proposed de novo proteins.
   While working at Bristol she showed, with Ray Swann, that the oxytocin hormone is produced in the corpus luteum of the ovary in sheep and other ruminants, as well as in the neurohypophysis. This might form part of the mechanism by which female ruminants detect whether or not they have conceived. She has subsequently studied how hormonal and other factors regulate the oestrus cycle and the birthing process in sheep and cows.
  
  Section::::Awards and societies.
   In addition to all of the above, the brain and spinal cord contain extensive circuitry to control the autonomic nervous system, which works by secreting hormones and by modulating the "smooth" muscles of the gut.
  
  Section::::Function.:Arousal.
  
  Many animals alternate between sleeping and waking in a daily cycle. Arousal and alertness are also modulated on a finer time scale by a network of brain areas.
   Interestingly, it has been shown that the sleep-wake cycle acts on the beta-amyloid burden which is a central component found in AD. Indeed, during waking, the production of beta-amyloid protein will be more consistent than during sleep. This is explained by two phenomena. The first is that the metabolic activity will be higher during waking and thus will secrete more beta-amyloid protein. The second is that oxidative stress will also be higher and lead to increased AB production.
   Large parts of the brain that are activated and sending signals during waking are inactive during NREM sleep and become reactivated during REM sleep. It is based on the fact that the brain and its neural circuitry is plastic and self-regulating, especially in its own activation and inactivation. This was observed by two experiments: development of sleepiness after dopamine neuron destruction in substantia nigra in the midbrain, and discovery of the reticular activating system, which are visual cues received through our eyes and to our brain that begin the waking process, that waking consciousness depends sleep. Following these studies, it became clear that activity levels and quality of consciousness were functions of brain activation and deactivation.
   Hormones are used to communicate between organs and tissues for physiological regulation and behavioral activities, such as digestion, metabolism, respiration, tissue function, sensory perception, sleep, excretion, lactation, stress, growth and development, movement, reproduction, and mood.
   Sleep increases the sensory threshold. In other words, sleeping persons perceive fewer stimuli, but can generally still respond to loud noises and other salient sensory events.
  
  During slow-wave sleep, humans secrete bursts of growth hormone. All sleep, even during the day, is associated with secretion of prolactin.
   Olfactory stimuli are important for sexual reproduction and neuroendocrine function in many species. For instance if a pregnant mouse is exposed to the urine of a 'strange' male during a critical period after coitus then the pregnancy fails (the Bruce effect). Thus, during coitus, a female mouse forms a precise 'olfactory memory' of her partner that persists for several days.
  
  Pheromonal cues aid synchronization of oestrus in many species; in women, synchronized menstruation may also arise from pheromonal cues, although the role of pheromones in humans is disputed.
  
  Section::::Function.:Stimulation.:Blood-borne stimuli.
   Oestrogen peaks at about 11 am on the day of proestrus. Between then and midnight there is a surge in progesterone, luteinizing hormone and follicle-stimulating hormone, and ovulation occurs at about 4 am on the next, estrus day. The following day, metestrus, is called early diestrus or diestrus I by some authors. During this day the corpora lutea grow to a maximal volume, achieved within 24 hours of ovulation. They remain at that size for three days, halve in size before the metestrus of the next cycle and then shrink abruptly before estrus of the cycle after that. Thus the ovaries of cycling rats contain three different sets of corpora lutea at different phases of development.
   Sleep onset is finally induced by sleep-promoting neurons, located in the ventrolateral preoptic nucleus (VLPO). The sleep-promoting neurons are believed to project GABA type A and galanin, two known inhibitory neurotransmitters, to arousal-promoting neurons, such as histaminergic, serotonergic, orexinergic, noradrenergic, and cholinergic neurons (neurons mentioned above). Levels of acetylcholine, norepinepherine, serotonin, and histamine decrease with the onset of sleep, for they are all wakefulness promoting neurotransmitters. Therefore, it is believed that the activation of sleep-promoting neurons causes the inhibition of arousal-promoting neurons, which leads to sleep. Evidence has shown that during the sleep-wake cycle, sleep-promoting neurons and the arousal-promoting neurons have reciprocal discharges, and that during NREM sleep, GABA receptors increase in the arousal-promoting neurons. This had led some to believe that the increase of GABA receptors in the arousal-promoting neurons is another pathway of inducing sleep.
   Von Economo, in his studies, noticed that lesions in the connection between the midbrain and the diencephalon caused prolonged sleepiness and therefore proposed the idea of an ascending arousal system. During the past few decades major ascending pathways have been discovered with located neurons and respective neurotransmitters. This pathway divides into two branches: one that ascends to the thalamus and activates the thalamus relay neurons, and another one that activates neurons in the lateral part of the hypothalamus and the basal forebrain, and throughout the cerebral cortex. The cell group involved in the first pathway is an acetylcholine-producing cell group called pedunculopontine and laterodorsal tegmental nucleus(PPT/LDT). These neurons play a crucial role in bridging information in between the thalamus and the cerebral cortex. These neurons have high activation during wakefulness and during REM sleep and a low activation during NREM sleep. The second branch originates from monoaminorgenic neurons. These neurons are located in the locus coeruleus, dorsal and median raphe nuclei, ventral periaqueductal grey matter, and tuberomammillary nucleus. Each group produces a different neurotransmitter. The neurons in the locus coeruleus produce noradrenaline, as fore the neurons in the dorsal and median raphe nuclei, ventral periaqueductal grey matter, and tuberomammillary nucleus produce serotonin, dopamine and histamine respectively. They then project onto the hypothalamic peptidergic neurons, which contain melanin-concentrated hormones or orexin, and basal forebrain neurons which contain GABA and acetylcholine. These neurons then project onto the cerebral cortex. It has also been discovered that lesions to this part of the brain cause prolonged sleep or may produce coma.
   BULLET::::- Sulfur dioxide.
  
  Endogenous transcription factors are those manufactured by the cell, as distinguished from cloned transcription factors.
  
  Endogenous substances typically have some physiological utility. However substances can also be pathologically endogenous. For example, in auto-brewery syndrome, ethanol is endogenously produced within the digestive system through endogenous fermentation of sugars.
   Hormone secretion may occur in many tissues. Endocrine glands are the cardinal example, but specialized cells in various other organs also secrete hormones. Hormone secretion occurs in response to specific biochemical signals from a wide range of regulatory systems. For instance, serum calcium concentration affects parathyroid hormone synthesis; blood sugar (serum glucose concentration) affects insulin synthesis; and because the outputs of the stomach and exocrine pancreas (the amounts of gastric juice and pancreatic juice) become the input of the small intestine, the small intestine secretes hormones to stimulate or inhibit the stomach and pancreas based on how busy it is. Regulation of hormone synthesis of gonadal hormones, adrenocortical hormones, and thyroid hormones is often dependent on complex sets of direct influence and feedback interactions involving the hypothalamic-pituitary-adrenal (HPA), -gonadal (HPG), and -thyroid (HPT) axes.
   Peptide hormones and protein hormones consist of three (in the case of thyrotropin-releasing hormone) to more than 200 (in the case of follicle-stimulating hormone) amino acid residues and can have a molecular mass as large as 31,000 grams per mole. All hormones secreted by the pituitary gland are peptide hormones, as are leptin from adipocytes, ghrelin from the stomach, and insulin from the pancreas.
  
  Section::::The endocrine system.:Hormones.:Steroid.
   The discovery of hormones and endocrine signaling occurred during studies of how the digestive system regulates its activities, as explained at Secretin § Discovery.
  
  Section::::Discovery.:Arnold Adolph Berthold (1849).
   Oxytocin and vasopressin (also called anti-diuretic hormone), the two neurohypophysial hormones of the posterior pituitary gland (the neurohypophysis), are secreted from the nerve endings of magnocellular neurosecretory cells into the systemic circulation. The cell bodies of the oxytocin and vasopressin neurons are in the paraventricular nucleus and supraoptic nucleus, respectively, and the electrical activity of these neurons is regulated by afferent synaptic inputs from other brain regions. By contrast, the hormones of the anterior pituitary gland (the adenohypophysis) are secreted from endocrine cells that, in mammals, are not directly innervated, yet the secretion of these hormones (adrenocorticotrophic hormone, luteinizing hormone, follicle-stimulating hormone, thyroid-stimulating hormone, prolactin, and growth hormone) remains under the control of the hypothalamus. The hypothalamus controls the anterior pituitary gland via "releasing factors" and "release-inhibiting factors"; these are blood-borne substances [author means via bloodstream and not by the lymphatic system nor air, nor any other modes of transport] released by hypothalamic neurons into blood vessels at the base of the brain, at the median eminence. These vessels, the hypothalamo-hypophysial portal vessels, carry the hypothalamic factors to the anterior pituitary, where they bind to specific receptors on the surface of the hormone-producing cells.
   There is some supporting evidence of the restorative function of sleep. The sleeping brain has been shown to remove metabolic waste products at a faster rate than during an awake state. While awake, metabolism generates reactive oxygen species, which are damaging to cells. In sleep, metabolic rates decrease and reactive oxygen species generation is reduced allowing restorative processes to take over. It is theorized that sleep helps facilitate the synthesis of molecules that help repair and protect the brain from these harmful elements generated during waking. The metabolic phase during sleep is anabolic; anabolic hormones such as growth hormones (as mentioned above) are secreted preferentially during sleep.
  
raw_presuppositions: The production of some bodily hormones are inhibited by sleep.  Some bodily hormones are only produced when we sleep. Some bodily hormones are only produced when we sleep. Some bodily hormones only undergo production during sleep.  Certain bodily hormones are only created during sleep.  Some bodily hormones are only produced when we sleep.
raw_corrections: Sleep alone does not produce bodily hormones, however what occurs during human sleep is likely the cause of these bodily hormones being produced during sleep.  Multiple things that humans do during their sleep are the reason for the production of the bodily fluids, and not the sleep itself  The production of the bodily hormones are not due to the sleep itself, but more so due to the circumstances that humans are in whilst they sleep. Sleep itself does not inhibit the production of bodily hormones, however what humans do during their sleep play a big factor. Sleep itself does not influence the production of bodily hormones, however the hormones are likely influenced by multiple circumstances that occur while you are asleep.  There are likely a large number of environmental factors associated with sleep that do not produce bodily hormones because of sleeping.