Yes, in a "normal" individual, there is a cortisol response to sleeping and waking. There is a cortisol response to eating too. And probably to sitting and standing and sneezing. Or to any one of a million thing that we do, everyday. The point is that a CAH person doesn’t make cortisol. Any cortisol that they get is what they get through medication. So, when we talk about dosing and how best to achieve it, what we are trying to determine is if there is a way that we can reasonably give cortisol that will cover ALL those situations in the day. This is where the idea of dosing around circadian rhythm comes in. It is the BIG PICTURE of what happens in terms of cortisol needs over the course of 24-hours, so that we can break it down into 3-4 convenient dosing periods during the day, rather than give teeny bits of cortisol everytime the body would normally need it.
Yes, I suppose the ideal would be to have a built-in sensor and injection system that could respond to our children’s daily needs, but that is not available, at this point. However, by understanding the general circadian pattern of ACTH secretion, we can make some pretty good assumptions about when to give meds, and about how much. And, luckily, unless there is a sleep disorder or something, by understanding circadian rhythm, we also know that we can do pretty much the same thing everyday---and it will generally work---even if we decide to have a nap on Sunday (but no nap on Tuesday). Or if we have lunch at 2 pm on Monday, instead of at noon. (All situations that would normally cause a cortisol response.)
No, of course, I am not saying that at precisely 8:00 on the dot, every morning, everyone’s ACTH levels peak at exactly the same moment. It might be 7:35 for one individual, 8:35 for another. So, yes, I would agree that it really doesn’t a difference if you dose at 6:30 am or at 7:30, or even if you do it at slightly different times everyday....by all means, do it whenever your child wakes up and it’s convenient, as long as it’s around the right general time.
The point I AM trying to make, however, is that as a child transitions from infant to toddler, and has a slightly different schedule of eating, sleeping, etc., his/her particular circadian pattern will persist. And as that child turns into a teenager and adult, and has even more different habits, that same circadian pattern will also still persist. In THAT way, the rhythm is essentially constant, and not governed by specific day-to-day activities.
And, yes, of course one’s circadian pattern will shift after a while, if one changes time zones. As I mentioned earlier, circadian rhythms appear to be regulated by cycles of light and dark, and different parts of the world are not light and dark, at the same time...so, yes, if you move to a different time zone, eventually your brain will adjust. As, yes, one’s circadian clock can get all messed up if you work nights and sleep days (and, thus, get light and dark cycles all mixed up.) But, those are the exceptions to the rule, and I am assuming that is not what we are discussing, right now.
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| 1: Recent Prog Horm Res 1999;54:97-130; discussion 130-2 | Related Articles, [unauthorised script deleted] language=JavaScript1.2>Links |
Circadian and sleep-dependent regulation of hormone release in humans.
Czeisler CA, Klerman EB.
Circadian, Neuroendocrine, and Sleep Disorders Section, Brigham and Women’s Hospital, Boston, Massachusetts 02115, USA.
Daily oscillations characterize the release of nearly every hormone. The circadian pacemaker, located in the suprachiasmatic nucleus of the hypothalamus, generates circadian, approximately 24-hour rhythms in many physiologic functions. However, the observed hormonal oscillations do not simply reflect the output of this internal clock. Instead, daily hormonal profiles are the product of a complex interaction between the output of the circadian pacemaker, periodic changes in behavior, light exposure, neuroendocrine feedback mechanisms, gender, age, and the timing of sleep and wakefulness. The interaction of these factors can affect hormonal secretory pulse frequency and amplitude, with each endocrine system differentially affected by these factors. This chapter examines recent advances in understanding the effects on endocrine rhythms of a number of these factors. Sleep exerts a profound effect on endocrine secretion. Sleep is a dynamic process that is characterized by periodic changes in electrophysiologic activity. These electrophysiologic changes, which are used to mark the state and depth of sleep, are associated with periodic, short-term variations in hormonal levels. The secretion of hormones such as renin and human growth hormone are strongly influenced by sleep or wake state, while melatonin and cortisol levels are relatively unaffected by sleep or wake state. In addition, sleep is associated with changes in posture, behavior, and light exposure, each of which is known to affect endocrine secretion. Furthermore, the tight concordance of habitual sleep and wake times with certain circadian phases has made it difficult to distinguish sleep and circadian effects on these hormones. Specific protocols, designed to extract circadian and sleep information semi-independently, have been developed and have yielded important insights into the effects of these regulatory processes. These results may help to account for changes in endocrine rhythms observed in circadian rhythm sleep disorders, including the dyssomnia of shift work and visual impairment. Yet to be fully investigated are the interactions of these factors with age and gender. Characterization of the factors governing hormone secretion is critical to understanding the temporal regulation of endocrine systems and presents many exciting areas for future research.
Publication Types:
PMID: 10548874 [PubMed - indexed for MEDLINE]