Low blood potassium levels can be first sign of Cushing’s disease

In case report, man, 48, had surgery to remove pituitary macroadenoma

Patricia Inácio, PhD avatar

by Patricia Inácio, PhD |

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Severe hypokalemia, or extremely low blood potassium levels, may be the first manifestation of Cushing’s disease, as illustrated in a recent case report.

The study described the case of a 48-year-old man with Cushing’s disease who had surgery to remove a pituitary macroadenoma, or a large pituitary tumor, but who had no classical signs of the condition.

“This unique presentation underscores the diverse clinical manifestations of [Cushing’s] and emphasizes the diagnostic challenges encountered in clinical practice,” the researchers wrote.

The study, “Unveiling the Uncommon: Cushing’s Syndrome (CS) Masquerading as Severe Hypokalemia,” was published in the journal Cureus.

Cushing’s syndrome is marked by unusually high levels of a hormone called cortisol. Cushing’s disease is a form of Cushing’s syndrome where high cortisol levels are caused by a tumor in the brain’s pituitary gland. Such tumors produce and release excessive amounts of adrenocorticotropic hormone (ACTH) — a molecule that signals the adrenal glands above the kidneys to produce cortisol.

High cortisol levels ultimately cause Cushing’s classical symptoms, including obesity, high blood pressure (hypertension), and muscle weakness.

However, Cushing’s “can demonstrate diverse and atypical features, challenging conventional diagnostic paradigms.”

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Severe hypokalemia first symptom of Cushing’s in man

Here, a team of international researchers described the case of a man with Cushing’s whose first symptom was severe hypokalemia.

The man, age 48, developed swelling in both legs, along with occasional shortness of breath, dizziness, and a general feeling of malaise. These symptoms, which went on for 10 days, led him to consult his primary care physician. At that time, he also reported drinking higher quantities of water and the need to urinate frequently. He had been diagnosed with hypertension eight months ago.

In the previous two months, he had experienced worsening muscle weakness impairing his ability to perform daily activities, including using the bathroom.

Blood work revealed the presence of hypokalemia, and he was referred to the hospital. When admitted, his blood pressure was high, but other vital signs were normal.

A physical examination revealed fine tremors and fluid retention that caused swelling in the lower part of the body. These symptoms were accompanied by a distended abdomen and reduced air entry into the lungs on auscultation. Blood tests confirmed the presence of hypokalemia and abnormally low levels of magnesium, as well as lactic acidosis, which occurs when there’s too much lactic acid in the body.

He received magnesium and potassium replacement treatment, as well as saline solution to keep his body hydrated.

A chest X-ray revealed pneumonia affecting several regions in both lungs. He received treatment with the antibiotics ceftriaxone and clarithromycin for a week.

Overall, his symptoms and clinical findings were suggestive of Conn’s syndrome, a condition in which the adrenal glands make too much the steroid hormone aldosterone. Blood work showed his aldosterone levels were below normal, ruling out Conn’s syndrome. However, his cortisol levels were markedly elevated.

His blood cortisol levels remained high after a low-dose dexamethasone suppression test. His urine cortisol levels were also elevated. The dexamethasone suppression 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.

A subsequent test confirmed he also had elevated levels of ACTH. His blood cortisol levels dropped after a high-dose dexamethasone suppression test, consistent with the presence of Cushing’s disease.

A CT scan of the adrenal glands came back normal, but a brain MRI revealed the presence of a pituitary macroadenoma, confirming the diagnosis of Cushing’s disease. He was referred for surgery to remove it.

Overall, “our case report highlights the rarity of severe hypokalemia as the initial presentation of [Cushing’s],” the researchers wrote. “A multidisciplinary approach involving endocrinologists, neurosurgeons, and radiologists is essential for the timely diagnosis and management of [Cushing’s].”