Physicians should consider the possibility of Cushing’s disease in patients presenting with an adrenal tumor normally associated with other forms of Cushing’s syndrome, a case report suggests.
The report, “Coexistence Of Cushing Disease With A Solitary Acth-Dependent Adrenal Adenoma,” was published in the journal AACE Clinical Case Reports.
Cushing’s syndrome is caused by the excessive production of the hormone cortisol by the adrenal glands, which sit atop the kidneys.
In approximately 65% of the cases, excessive cortisol production is triggered by a tumor in the pituitary gland — a small pea-size gland in the brain — that produces abnormally high levels of the adrenocorticotropic hormone (ACTH). This condition, also known as Cushing’s disease, is a form of ACTH-dependent Cushing’s syndrome.
However, in about 30% of the cases, Cushing’s syndrome is triggered by tumors in the adrenal glands that produce too much cortisol, or by the excessive activity of the glands themselves. All these are known as ACTH-independent forms of Cushing’s syndrome.
Here, researchers at the Walter Reed National Military Medical Center in Bethesda, Maryland, described the case of a woman who had very mild symptoms of Cushing’s syndrome and was later found to have an adrenal tumor (adenoma) along with classic ACTH-dependent Cushing’s disease.
The 49-year-old woman originally was admitted to the hospital for urosepsis, a type of blood poisoning resulting from a urinary tract infection. She also explained she had been feeling tired and less able to withstand physical exertion, especially when climbing stairs, for several months.
An abdominal computed tomography (CT) scan revealed she had an adenoma measuring 2.7 cm in her right adrenal gland. A physical exam performed afterward revealed she had very mild features of Cushing’s syndrome, including mild facial roundness that was not accompanied by central obesity, striae (ridges), or muscle weakness.
Lab tests showed that even though her blood cell counts and electrolyte levels were within normal range, her cortisol levels in the blood (23.0 micrograms per decilitre, mcg/dl; normal range: less than 7.5 mcg/dl) and urine (294 mcg; normal range: 4.0–50.0 mcg) both were elevated, which was consistent with the diagnosis of Cushing’s syndrome.
An overnight dexamethasone suppression test confirmed the woman had hypercortisolism (excessively high levels of cortisol in the blood), with her blood cortisol levels only dropping by 40% after the test. This test measures the levels of cortisol in the blood in the morning after patients take a tablet of dexamethasone, a corticosteroid that normally blocks its production.
At the same time, physicians also found her blood ACTH levels were abnormally high (39 picograms per milliliter, pg/mL; normal range: 5–27 pg/mL).
They performed a corticotropin-releasing hormone (CRH) stimulation test. This test is normally performed to identify the source of excess ACTH in the body. It is based on the principle that pituitary tumors usually respond to CRH stimulation by increasing ACTH production, while other tumors typically do not respond to stimulation.
After performing this test, clinicians found her ACTH levels increased by 50%, while her cortisol levels also increased by 41%, consistent with the presence of a pituitary tumor. This was confirmed after the patient had a brain MRI scan.
She then had surgery to remove the pituitary tumor, which later was confirmed to be an ACTH-producing lesion. After surgery, her blood cortisol levels dropped below the normal range, and she was started on hydrocortisone to normalize them for the following 10 months.
An abdominal CT scan performed six months later revealed her adenoma had decreased in size to 1.8 cm, which indicated the tumor might be partially dependent on ACTH to maintain its growth.
“This case highlights the importance of recognizing the coexistence of ACTH-dependent Cushing’s disease with an adrenal adenoma and partial ACTH dependency of the adrenal adenoma,” the researchers wrote.
They also noted “it is important to search for a pituitary or ectopic source of ACTH in a patient with an adrenal adenoma coexisting with Cushing’s syndrome and an elevated plasma ACTH level.”
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