In persons on schedules of diurnal activity and nocturnal sleep, the blood and urine concentrations of adrenocorticosteroid hormones drop a night and rise to highest levels in early morning. The course of the adrenal cycle may also be followed by measuring the eosinophil (white-blood-cell) level; eosinophils decrease as the blood level of adrenal hormones increases.
Light is probably the synchronizer of the adrenocorticisteroid rhythm. This has implications for people who are night workers or who have varying degrees of blindness. Since adrenal hormones control other circadian rhythms within the body, knowledge of their cycle is important in the study and treatment of numerous conditions.
Low blood levels of adrenal hormones affect the nervous system and cause a person to be more sensitive to sounds, tastes, and smell. Sensory acuity reaches its maximum at the time of lowest steroid levels. A sudden drop in acuity occurs in the early morning as steroid levels begin to rise. A person is therefore better able to detect taste, smell, or sound at the end of the day. Daily fatigue from lack of sleep and neurologically-related symptoms associated with adrenal insufficiency (Addison`s disease) may be related to low levels of adrenal hormones.
Adrenal rhythm is also important in handling certain allergies. Sensitivity to histamine follows a circadian rhythm: it peacks about the time of evening or night when adrenocorticosteroids are reaching their lowest levels. Nasal congestion from hayfever, skin reactions from drug sensitivity, and breathing crises in asthma patients occur more frequently during the evening or night.
References :
United States Department of Health, Education, and Welfare, Public Health Service, Biological Rhythms in Psychiatry and Medicine. Chevy Chase, M.d.: National Institute of Mental Health, 1970.
Murray, RB and Zentner JP., Nursing Concepts for Health Promotion, Second Edtion, Prentice-Hall, Inc, Englewood Cliffs, N.J, 1979.
