Circadian rhythm is not merely about sleep and wake cycles. The deeper one goes into the topic; better a person understands that almost every bodily process has a rhythm. During the daytime, humans need more energy, better stress handling abilities. While in the evening, the body must relax, before one goes to bed.
Adrenocorticotropic hormone (ACTH) is part of the hypothalamic-pituitary-adrenal (HPA) axis. It is one of the anterior pituitary hormones. It plays a vital role in stress management. ACTH stimulates the production of corticosteroids from the adrenal gland. It increases levels of cortisol, a hormone that helps fight stress. ACTH also increases levels of aldosterone, thus increasing water retention, and increasing blood pressure.
ACTH and Circadian Rhythm Explained
ACTH also affects cholesterol metabolism. It promotes delivery of cholesterol to the mitochondria. It also helps regulate levels of sex hormones like testosterone and estrogen. ACTH reduces cholesterol levels in the blood, at the same time increasing its availability to adrenal glands.
ACTH is vital in stress management. Two critical factors control its levels in the body. Negative feedback – that is high cortisol levels suppress its production. And circadian rhythm.
Research shows that levels of ACTH are at peak in the early morning (6 to 9 AM). Its levels keep declining during the day and are lowest between 23:00 to 02:00 hours.
If circadian rhythm changes, it alters ACTH rhythm thus disturbing various metabolic activities. On the other hand, if ACTH rhythm or secretion changes (like due to jet lag or emotional stress) it changes the circadian rhythm. In short, both circadian rhythm and release of ACTH are interrelated.
It explains how stress can be bad for metabolism, sleep, and cause diseases.
When a person is chronically stressed, cortisol levels are abnormally high. It happens due to activation of other components of the HPA axis in the brain. When cortisol levels are high, it results in dysregulation of ACTH. Dysregulated ACTH alters secretion of melatonin, thus affecting circadian rhythm. It explains why a stressed person is tired, yet cannot sleep sufficiently.
Dysregulation of ACTH and consequently glucocorticoids can affect the functioning of almost every body organ. See Figure 1 (stress dysregulates ACTH, normal circadian rhythm normalizes ACTH levels).
Further, research shows that those having difficulty in sleeping also have higher ACTH levels. These people are in hyperarousal state. The person in stress always has trouble sleeping.
Figure 1 ACTH and glucocorticoids dysregulation and health effects (Source: 1. Chung S, Son GH, Kim K. Circadian rhythm of adrenal glucocorticoid: Its regulation and clinical implications. Biochimica et Biophysica Acta (BBA) – Molecular Basis of Disease. 2011;18)
How does age affect ACTH?
Research shows that hyperactive HPA axis, high levels of ACTH accelerate aging. On the other hand, with age HPA axis becomes hypersensitive. It explains why with age a person becomes more prone to stress. Moreover, it also says that stress can fasten aging processes.
Studies confirm that in stressed adults, with high ACTH, dysregulated circadian rhythm; there is fast mental decline. It means that stress and aging both reduce sleep. Reduced sleep is damaging to the brain.
All this means that stress regulation can normalize levels of cortisol. It can help regulate ACTH, normalize response of HPA axis. All this may help normalize circadian rhythm resulting in sufficient sleep and good health.
- Lim CT, Khoo B. Normal Physiology of ACTH and GH Release in the Hypothalamus and Anterior Pituitary in Man. In: De Groot LJ, Chrousos G, Dungan K, et al., eds. Endotext. South Dartmouth (MA): MDText.com, Inc.; 2000. Accessed November 3, 2018.
- Chung S, Son GH, Kim K. Circadian rhythm of adrenal glucocorticoid: Its regulation and clinical implications. Biochimica et Biophysica Acta (BBA) – Molecular Basis of Disease. 2011;1812(5):581-591. doi:10.1016/j.bbadis.2011.02.003
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