Rare Chest Tumor Causes Cushing’s Syndrome in Chinese Man
A mediastinal paraganglioma, an extremely rare tumor located between the lungs, was found to be the cause of Cushing’s syndrome in a 40-year-old Chinese policeman, according to a recent case report.
Doctors were particularly challenged by this case because the patient also had a pituitary tumor, which could have been the source of excessive cortisol levels associated with Cushing’s. The laboratory tests used to discriminate between the two potential culprits were inconsistent.
The report, “Case Report: An Unusual Case of Ectopic ACTH Syndrome Caused by Mediastinal Paraganglioma,” was published in the journal Frontiers in Endocrinology.
Cushing’s syndrome comprises a series of diseases characterized by excessive cortisol levels, a condition also known as hypercortisolism. In most cases, it is caused by tumors in the brain’s pituitary gland that produce high levels of adrenocorticotropic hormone (ACTH), which triggers cortisol production in the adrenal glands. This specific form of the condition is known as Cushing’s disease.
However, ACTH-producing tumors can also be found outside the pituitary gland, particularly in the lungs, in which case the condition is referred to as ectopic Cushing’s syndrome.
Researchers from China now reported the case of man with an ACTH-producing tumor in a location where these types of tumors rarely occur: the mediastinum, or the space in the chest between the lungs.
The tumor was a paraganglioma, which is derived from the abnormal growth of nerve cells, called chromaffin cells, that are involved in important functions such as blood pressure regulation.
“Based on literature reviews, less than 20 cases were reported about ACTH-secreting paraganglioma, and only 4 cases were described to originate from the mediastinum,” the researchers wrote.
According to researchers, the man was admitted to their Endocrinology Unit complaining of whole-body swelling, limb weakness, extreme thirstiness, and excessive urination.
“My body was very strong before I got sick. But I became very weak since more than 1 year ago. I felt tired every day. There was no strength in my limbs, especially in the lower limbs. My mood got worse gradually, lazy words, and depression,” the patient stated.
He had classical symptoms of Cushing’s syndrome, including obesity around his midsection, rounded face (moon face), excessive fat accumulation between the shoulders (“buffalo hump”), and skin bruising.
Lab tests also revealed he had high levels of cortisol in the blood (2,247 nanomoles per liter (nmol/L); normal range: 147–609 nmol/L) and urine (9,174 micrograms per 24h (mcg/24h); normal range: 20–128 mcg/24h), as well as high ACTH levels (162 nanograms per liter (ng/L); normal range: 5–78 ng/L).
A high-dose dexamethasone suppression test, which is typically carried out to help doctors identify the cause of hypercortisolism, lowered his 24-hour urinary cortisol levels by more than 50%. Yet its ability to suppress ACTH and cortisol levels in the blood was reduced. In Cushing’s disease, ACTH should be suppressed by a high dose of dexamethasone.
Next, researchers performed a desmopressin stimulation test. In this exam, administered desmopressin increases ACTH and cortisol levels in patients with Cushing’s disease, but not in most healthy people or in those with ACTH-producing tumors found outside the pituitary or adrenal glands. After this test, ACTH levels rose by 836% compared with baseline.
Imaging examinations revealed the presence of a suspected pituitary tumor, as well as a nodule in the mediastinum. To ultimately find out which tumor was causing ACTH and cortisol to be excessively high, doctors performed petrosal sinus sampling, a procedure in which blood samples are collected from each side of the veins draining the pituitary gland.
In Cushing’s disease, ACTH levels from the pituitary drainage are expected to be higher than the hormone levels in the bloodstream. The combination of this test with the administration of desmopressin revealed that ACTH levels were not increased in the petrosal sinus compared with peripheral blood before and after desmopressin stimulation.
The mediastinal nodule was surgically removed, and further analyses confirmed it was an ACTH-producing tumor. Following surgery, the patient’s ACTH levels dropped to 13 ng/L and his cortisol levels to 224 nmol/L.
“After the operation, my muscle strength became better, and the mood significantly improved. At 1 to 2 months later, my symptoms gradually disappeared. Now I can come to the clinic for follow-up visits by myself, and I have resumed my routine work,” the patient said.
Researchers noted that although the patient was in total clinical remission at 16 months post-surgery, his follow-up is still ongoing.