Inhaled corticosteroids (ICS) are a primary treatment for managing chronic inflammatory lung diseases like asthma and COPD. These medications work by reducing airway inflammation to control symptoms and prevent exacerbations. The adrenal glands, located on top of the kidneys, produce cortisol. This hormone helps regulate metabolism, control blood pressure, and manage the body’s response to stress. While ICS are designed for local action in the lungs, the medication can be absorbed into the bloodstream. This systemic absorption creates a potential risk of interfering with adrenal gland function, a condition known as adrenal insufficiency.
The Mechanism of Adrenal Suppression
The body’s cortisol production is managed by the Hypothalamic-Pituitary-Adrenal (HPA) axis, a feedback system that maintains hormonal balance. The hypothalamus in the brain produces a hormone (CRH) that signals the pituitary gland to release adrenocorticotropic hormone (ACTH). ACTH then travels to the adrenal glands, instructing them to produce cortisol. When cortisol levels are sufficient, the hypothalamus and pituitary gland reduce their signaling to prevent overproduction.
Inhaled steroids are synthetic versions of glucocorticoids, the class of hormones that includes cortisol. When ICS are absorbed into the bloodstream, the body may not distinguish them from its own naturally produced cortisol. The brain’s regulatory centers perceive high levels of cortisol and suppress the HPA axis. This action slows or stops the production of CRH and ACTH, which in turn causes the adrenal glands to become dormant.
This downregulation of the HPA axis is known as adrenal suppression. If the use of inhaled steroids is prolonged, the adrenal glands can lose their ability to produce cortisol independently, leading to secondary adrenal insufficiency.
Identifying Key Risk Factors
Several factors influence the likelihood of developing adrenal insufficiency from inhaled steroid use, and the risk increases with greater systemic exposure.
- The dose and potency of the corticosteroid are significant, with high daily doses or more potent medications like fluticasone carrying a greater risk compared to others like budesonide.
- Long-term, continuous use presents a greater risk than short-term or intermittent therapy.
- Concurrent use of other steroid forms, such as nasal sprays for allergies or topical creams for eczema, increases the total systemic steroid load.
- Children are more susceptible to the systemic effects of ICS due to their smaller body size and developing metabolic systems.
- Individual differences in liver function and metabolism can affect how quickly the body processes and clears the synthetic steroid, with slower clearance increasing risk.
Symptoms of Adrenal Insufficiency
The symptoms of adrenal insufficiency often develop gradually and are non-specific, making them easy to attribute to other causes. Chronic signs can include persistent fatigue, muscle weakness, loss of appetite, and unexplained weight loss. Because these symptoms overlap with many other conditions, a high degree of clinical suspicion is often required to connect them to adrenal suppression.
A more severe manifestation is an adrenal crisis, a life-threatening medical emergency. This can be triggered by a significant physical stressor, like an infection or injury, in someone with underlying adrenal suppression. During these times, a healthy body would normally produce a surge of cortisol to cope, but a suppressed system cannot mount this response.
Symptoms of an adrenal crisis are sudden and severe. They can include intense pain in the lower back, abdomen, or legs, along with severe vomiting and diarrhea leading to dehydration. Other signs are a sharp drop in blood pressure, confusion, or loss of consciousness. An adrenal crisis requires immediate emergency medical treatment.
Diagnosis and Treatment Pathways
Diagnosis begins when a patient’s symptoms and risk factors raise suspicion. A healthcare provider can order a blood test to measure the morning cortisol level. If the result is abnormally low, further testing is required to assess the function of the HPA axis.
The primary confirmatory test is the ACTH stimulation test. This procedure measures the baseline cortisol level before and after an injection of synthetic ACTH. A healthy adrenal system responds by producing a significant amount of cortisol, while a suppressed system shows a minimal or absent response.
Management of ICS-induced adrenal insufficiency focuses on balancing the respiratory treatment with restoring adrenal function. Patients must not abruptly stop their inhaled steroid, as this can trigger an adrenal crisis. A physician will guide a gradual tapering of the ICS dose or switch the patient to a less potent steroid.
In cases of confirmed, significant suppression, a patient may be prescribed oral hydrocortisone to replace the cortisol their body is not producing. Patients are also educated on how to manage their condition during times of illness or stress, which may require a temporary increase in their steroid dose. This management is done under close medical supervision to maintain both respiratory and adrenal health.