Cortisol is a steroid hormone produced by the adrenal glands, which are small, triangle-shaped organs located on top of each kidney. This hormone plays a significant role in the body’s natural “fight or flight” response, helping to regulate stress. Beyond stress, cortisol influences various bodily functions, including metabolism of carbohydrates, fats, and proteins, blood pressure regulation, and the sleep-wake cycle. Cortisol levels in the body naturally fluctuate throughout the day.
Understanding Cortisol Measurement
Cortisol levels are commonly measured in micrograms per deciliter (ug/dl). This unit indicates the concentration of cortisol present in a deciliter of blood, making it a standard metric. There isn’t a single “normal” number for cortisol; instead, a “normal range” represents population-based averages.
The normal range for cortisol can vary between different laboratories due to variations in testing methods and equipment. Common methods include blood tests, saliva tests, and 24-hour urine tests. Blood tests often involve samples taken at specific times, such as 8 AM and 4 PM, to account for daily fluctuations. Saliva and urine tests also provide insights into cortisol patterns over time.
Cortisol Levels Across the Lifespan
Cortisol levels naturally change throughout a person’s life. For newborns, typical serum cortisol levels can range from 1 to 24 ug/dL.
In children aged 1 to 16 years, morning serum cortisol levels around 8 AM typically fall between 3 and 21 ug/dL, while afternoon levels around 4 PM are generally lower, ranging from 3 to 10 ug/dL. Research indicates that morning serum basal cortisol levels tend to increase with age and pubertal maturation in school-aged children and adolescents. For instance, studies have shown average cortisol levels of 10.7 mcg/dL at age 13 in boys and 11.1 mcg/dL at age 13 in girls, increasing to 14.4 mcg/dL and 15.9 mcg/dL respectively by age 16.
For healthy adults and older adults, morning serum cortisol levels, typically taken between 6 AM and 8 AM, generally range from 5 to 23 ug/dL. Later in the day, around 4 PM, these levels typically decrease, falling within the range of 3 to 13 ug/dL.
Factors Influencing Cortisol Levels Beyond Age
Beyond age, several factors can significantly influence cortisol levels. One significant influence is the diurnal rhythm, which refers to the natural daily fluctuation of cortisol.
Cortisol levels are typically highest in the early morning, often peaking around 30-40 minutes after waking, and gradually decline throughout the day, reaching their lowest point around midnight or during sleep. This pattern can be reversed for individuals who work night shifts, as their cortisol release aligns with their altered sleep-wake cycle.
Physical and psychological stress can temporarily elevate cortisol levels. When the body perceives stress, the hypothalamic-pituitary-adrenal (HPA) axis activates, leading to an increased release of cortisol. Chronic stress can lead to prolonged elevation of cortisol, potentially affecting various bodily systems.
Sleep patterns also play a role in cortisol regulation. Sleep deprivation or irregular sleep schedules can disrupt the natural circadian rhythm of cortisol, potentially leading to elevated levels, especially in the evening.
Certain medications, particularly corticosteroids, can significantly affect cortisol readings, as they mimic the effects of natural cortisol in the body. Therefore, it is often recommended to temporarily stop certain medications before a cortisol test.