Cortisol is a hormone that plays a crucial role in our body’s response to stress. Understanding how cortisol is produced can help differentiate between Cushing’s syndrome and Cushing’s disease and explain why specific lab work is ordered for these conditions.
The process begins with the interaction of several key structures: the hypothalamus, pituitary gland, adrenal glands (specifically the adrenal cortex), and a complex negative feedback loop in our body.
The production of cortisol starts when a person experiences stress. The brain detects this stress and signals the need for cortisol, the stress hormone. The hypothalamus, located in the brain, responds by releasing corticotropin-releasing hormone (CRH).
The prefix “cortico” in CRH hints at its role in cortisol production. CRH then stimulates the pituitary gland, particularly the anterior part, to release adrenocorticotropic hormone (ACTH). The prefix “adreno” in ACTH indicates its action on the adrenal glands.
Once ACTH is released, it stimulates the adrenal glands, specifically the cortex, to produce cortisol. Typically, cortisol is released in small doses for short periods. When the body detects sufficient cortisol levels, it signals the hypothalamus to stop CRH production, which in turn stops ACTH production, effectively maintaining balance in the system, hence using the negative feedback loop. However, this harmonious feedback loop can malfunction.
In some cases, the pituitary gland may develop tumors, causing excessive ACTH production and, consequently, too much cortisol. This condition is known as Cushing’s disease. Blood tests typically will show high levels of both ACTH and cortisol, indicating the pituitary gland as the source of the problem.
Conversely, in Cushing’s syndrome, the pituitary gland functions correctly, but the adrenal glands produce too much cortisol, often due to tumors or prolonged corticosteroid use. Lab work in this scenario usually reveals high cortisol and low ACTH levels. The body attempts to reduce ACTH production due to excess cortisol, but the adrenal glands continue to secrete cortisol regardless of feedback signals.
Understanding these mechanisms clarifies the differences between Cushing’s syndrome and Cushing’s disease.
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References:
Centers for Disease Control and Prevention. (2019, June 14). Cushing’s syndrome. https://www.cdc.gov/diabetes/library/features/cushings-syndrome.html
MedlinePlus. (2022, March 15). Cushing’s syndrome. U.S. National Library of Medicine. https://medlineplus.gov/cushingssyndrome.html
Nieman, L. K., & Biller, B. M. (2019). Cushing’s syndrome: Diagnosis and treatment. Journal of Clinical Endocrinology & Metabolism, 104(12), 5794-5802. https://doi.org/10.1210/jc.2019-00963
U.S. National Library of Medicine. (2022). Cushing’s syndrome. PubMed Health. https://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001392/