Corticosterone is a steroid hormone produced in the adrenal cortex from cholesterol. As a glucocorticoid hormone, it is involved in regulating a wide range of physiological processes. This hormone is associated with the body’s response to stress, helping to manage energy and immune function. It also contributes to the regulation of the sleep-wake cycle by promoting alertness during the day.
The Role of Corticosterone in the Body
Corticosterone plays a significant part in managing the body’s energy supply, particularly during periods of stress. It stimulates a process called gluconeogenesis, where the liver creates new glucose from substances like amino acids. This action ensures the brain and muscles have a ready source of fuel. The hormone also facilitates the breakdown of fats and proteins into molecules that can be used for energy.
The hormone also has a notable influence on the immune system. Corticosterone can dampen immune activity and reduce inflammation. In the short term, this effect is protective, as it prevents the immune system from overreacting to a stressor, which could cause tissue damage. This modulation helps the body focus its resources on the immediate threat.
Beyond metabolism and immunity, corticosterone affects cognitive functions like learning and memory. Acute, short-term increases in corticosterone levels can enhance the brain’s ability to form and recall memories, especially those associated with stressful events. This function is an adaptive mechanism, helping an organism remember and better respond to future threats.
Corticosterone Versus Cortisol
While both corticosterone and cortisol are glucocorticoid hormones involved in the stress response, their prevalence differs significantly across species. In humans, cortisol is the primary glucocorticoid, responsible for most stress-related hormonal signaling. Corticosterone is present in humans, but at much lower concentrations, where its effects are weaker than those of cortisol.
In many other animals, including rodents, reptiles, and birds, corticosterone is the dominant glucocorticoid. For these species, corticosterone performs the main duties of regulating energy, immune reactions, and stress responses. In humans, one of its main functions is to act as an intermediate molecule in the synthesis of other hormones. It is a precursor to aldosterone, a hormone that regulates blood pressure and electrolyte balance.
This distinction is a frequent point of confusion, but the key difference is which hormone takes the lead role in a particular species. While their functions are similar, their concentration and primary role are species-dependent. For humans, cortisol is the main actor in the stress response, with corticosterone playing a supportive role in hormone production.
Regulation Through the HPA Axis
The release of corticosterone is controlled by the Hypothalamic-Pituitary-Adrenal (HPA) axis, the body’s central command center for managing stress. The process begins when the hypothalamus perceives a stressor. In response, it secretes corticotropin-releasing hormone (CRH).
This release of CRH signals the pituitary gland, a small structure at the base of the brain, to secrete adrenocorticotropic hormone (ACTH) into the bloodstream. ACTH travels through circulation to the adrenal glands, situated on top of the kidneys. The arrival of ACTH at the adrenal cortex stimulates the production and release of glucocorticoids like corticosterone.
To prevent this stress response from continuing indefinitely, the HPA axis uses a negative feedback mechanism. As corticosterone levels rise in the bloodstream, the hormone signals the hypothalamus and pituitary gland. This instructs them to decrease their production of CRH and ACTH, shutting down the stress response and allowing the body to return to balance.
Health Implications of Imbalanced Levels
When the HPA axis is persistently activated by chronic stress, it can lead to chronically high levels of corticosterone and negative health consequences. Prolonged exposure can impair the immune system, making an individual more susceptible to infections. It can also lead to metabolic issues, including insulin resistance, changes in fat distribution, muscle weakness, and adverse impacts on the brain like memory difficulties.
Conversely, insufficient levels of corticosterone can also cause health problems. Chronically low levels can result in fatigue, low blood pressure (hypotension), and a diminished capacity to handle stress. This adrenal insufficiency means the body cannot mount an effective response to stressors. A primary example is Addison’s disease, where the adrenal glands are damaged and cannot produce enough hormones.