Hypothalamic-Pituitary-Adrenal Axis - The Stress Regulator

Introduction:

The hypothalamic-pituitary-adrenal axis, or the HPA axis, describes the interaction between the hypothalamus, pituitary gland, and adrenal glands. The HPA axis is a significant interaction, as it helps the body cope with stressful situations, in the absence of which it becomes difficult for the body to fight a challenging situation. Hypothalamus and the pituitary gland are two vital structures located at the base of the brain. Hypothalamus is connected to the pituitary by a band of nerves. Hypothalamus gives information to the pituitary gland to produce specific hormones, which are then redirected to the target organs, where they act. It also helps in maintaining an internal balance in the body. The result of the HPA axis is the production of the hormone cortisol, which allows the body to sustain stressful situations.

What Is Cortisol?

Cortisol, or stress hormone, is an important hormone released by the adrenal glands. The various functions of cortisol include:

• Helping the body use stored glucose to get enough energy to handle stress.

• Increasing the blood pressure that leads to redirecting more blood to the muscles, thereby readying them to fight the danger or run away from it.

• Inducing anti-inflammatory effects on the body by decreasing the secretion of pro-inflammatory substances like cytokines and histamines that trigger inflammation.

• Playing a role in learning and memory by temporarily blocking the emotional memories more when compared to neutral memories. It contributes to learning by helping in habit-based learning.

• Cortisol also shuts down the brain to avoid activities that are considered unimportant during times of stress.

Cortisol release continues for a few hours after experiencing stress. The circulating levels in the bloodstream are detected by areas of the brain called the hypothalamus and hippocampus. As a result, a negative feedback loop is created due to which there is a shutdown of the HPA axis, thereby reducing cortisol levels in the blood. The feedback loop is necessary for the body to help realize that it has reached a state of equilibrium or homeostasis. Therefore, the HPA axis is designed to help the body against extended HPA activity.

How Does the HPA Axis Work?

The HPA axis is activated to ultimately produce cortisol, a glucocorticoid hormone that helps the body prepare for an untoward situation, physically or mentally. The first step when the body experiences stress is the activation of the sympathetic nervous system, which causes the release of hormones, epinephrine, and norepinephrine, which increase the heart rate. After ten seconds of epinephrine release, the HPA axis gets activated.

After activation, the hypothalamus releases corticotropin-releasing hormone (CRH). CRH has two functions, one is increasing the activity of the sympathetic nervous system, and the second is activating the pituitary gland to release another hormone called adrenocorticotropic hormone (ACTH). ACTH reaches the adrenal glands, located on the top of the kidneys, through the bloodstream and activates them to produce glucocorticoid cortisol.

The adrenal gland comprises the outer adrenal cortex and the inner adrenal medulla. The medulla is activated during the initial stress response, releasing epinephrine, whereas the outer cortex is activated during the next stage by releasing cortisol.

What Happens When There Is an HPA Axis Dysfunction?

Though the HPA axis acts as a savior in stressful situations, it may sometimes have issues in functioning that leads to an overstimulation of the axis that can cause physical or psychiatric problems. HPA axis dysfunctioning can be due to the following reasons, that include:

• Genetic abnormalities.

• Biological causes, like medications.

• Early-life causes like childhood trauma.

• Everyday life stress.

The common symptoms noted due to a dysfunctioning HPA axis include:

1. Irritability.

2. Unexplained tiredness.

3. Frequent illness.

4. Feeling overwhelmed.

5. Difficulty in coping with stress.

6. Increased response to the slightest stress triggers.

In general, people with high levels of cortisol in the blood can experience the following:

• Suppressed immune system.

• Hypertension.

• Diabetes.

• Obesity.

• Insomnia.

• Weakness of muscles.

• Irregular menstrual cycle.

• Heart diseases.

What Is Cushing’s Syndrome?

Cushing’s syndrome or hypercortisolism is when the body produces high levels of the hormone cortisol, which stays for long periods in the bloodstream. The condition occurs either due to intake of high doses of corticosteroids or the body producing excess cortisol or ACTH. The symptoms of people with Cushing syndrome include:

• Weight gain.

• Acne.

• Deposits of fatty tissue.

• Delicate skin.

• Delayed healing of cuts and wounds.

What Does Chronic Stress Do to the Body?

Chronic stress due to unpleasant life experiences can cause a prolonged activation of the HPA axis, thereby causing increased cortisol production. Also, cortisol tends to remain in the blood for more extended periods. Chronic stress thereby increases the time for the body to return to a peaceful pre-stress phase. Repeated episodes or longer periods of stress can contribute to an overactivated HPA. Researchers believe that a prolonged HPA cycle in the body can contribute to various mental health and metabolic disorders. For example, mood disorders like anxiety, depression, mood swings, and irritability have been related to long-term elevation of cortisol levels.

How to Keep the HPA Axis Regulated Normally?

Depending on the situation, various measures can be taken to regulate the HPA axis to work normally. Identifying the cause and treating it has been proven to be helpful. The multiple options for regulation include:

1. Cushing’s syndrome causing excess cortisol can be managed with medications like Ketoconazole, Lysodren, and Metapirone.

2. A healthcare professional can modify the intake of medicines for other conditions that increase cortisol levels.

3. Mood disorders like anxiety and depression can be managed with anti-depressant medications. Psychotherapy or talk therapy is another option for treating severe cases that helps people deal with mental illnesses or emotional difficulties. CBT or cognitive behavioral therapy is a type of psychotherapy that has effectively treated traumatic conditions causing stress. Counseling sessions help people understand the reason for chronic stress and help them manage it better.

4. Biofeedback is a technique in which information about the internal body parts, like a fast heartbeat, is made to be heard by the person experiencing it. Biofeedback helps the person try to reduce the heartbeat and work on the techniques that help achieve it.

The lifestyle changes that can be incorporated to help regulate the HPA axis include:

• A healthy and nutritious diet that focuses on maintaining sugar levels within the range.

• Engaging in regular physical activity.

• Maintaining a regular sleep pattern and getting enough sleep.

• Avoiding alcohol and caffeine.

• Practicing relaxation techniques like deep breathing exercises, yoga, meditation, and mindfulness.

Conclusion:

The HPA axis plays a pivotal role in helping manage day-to-day stressful situations and chronic stress. It prepares the body for untoward instances by releasing cortisol, preparing the body for fight or flight. However, chronic stress triggers the HPA axis more than required, causing an overactivated system and symptoms that get difficult to manage. Proper recognition of the signs and receiving prompt treatment for the triggering cause can help people lead peaceful and productive lives.