BOSTON — The prevalence of Cushing syndrome (CS) in the United States may be considerably higher than currently appreciated, new data from a single US institution suggest.
In contrast to estimates of 1 to 3 cases per million patient-years from population-based European studies, researchers at the University of Wisconsin, Milwaukee, estimated that the incidence of CS in Wisconsin is a minimum of 7.2 cases per million patient-years. What’s more, contrary to all previous studies, they found that adrenal Cushing syndrome was more common than pituitary adrenocorticotropic hormone (ACTH)–secreting tumors (Cushing disease), and that fewer than half of individuals with adrenal Cushing syndrome had classic physical features of hypercortisolism, such as weight gain, round face, excessive hair growth, and stretch marks.
“Cases are absolutely being missed. ... Clinicians should realize that cortisol excess is not rare. It may not be common, but it needs to be considered in patients with any constellation of features that are seen in cortisol excess,” study investigator Ty B. Carroll, MD, associate professor of medicine, endocrinology and molecular medicine, and the endocrine fellowship program director at Medical College of Wisconsin in Milwaukee, told this news organization.
There are several contributing factors, he noted, “including the obesity and diabetes epidemics which make some clinical features of cortisol excess more common and less notable. Providers get used to seeing patients with some features of cortisol excess and don’t think to screen. The consequence of this is more difficult-to-control diabetes and hypertension, more advance metabolic bone disease, and likely more advanced cardiovascular disease, all resulting from extended exposure to cortisol excess,” he said.
Are Milder Cases the Ones Being Missed?
Asked to comment, session moderator Sharon L. Wardlaw, MD, professor of medicine at Columbia University College of Physicians and Surgeons, New York City, said, “When we talk about Cushing [syndrome], we usually think of pituitary ACTH as more [common], followed by adrenal adenomas, and then ectopic. But they’re seeing more adrenal adenoma ... we are probably diagnosing this a little more now.”
She also suggested that the Wisconsin group may have a lower threshold for diagnosing the milder cortisol elevation seen with adrenal Cushing syndrome. “If you screen for Cushing with a dexamethasone suppression test … [i]f you have autonomous secretion by the adrenal, you don’t suppress as much. ... When you measure 24-hour urinary cortisol, it may be normal. So you’re in this in-between [state]. ... Maybe in Wisconsin they’re diagnosing it more. Or, maybe it’s just being underdiagnosed in other places.”
She also pointed out that “you can’t diagnose it unless you think of it. I’m not so sure that with these mild cases it’s so much that it’s more common, but maybe it’s like thyroid nodules, where we didn’t know about it until everybody started getting all of these CT scans. We’re now seeing all these incidental thyroid nodules ... I don’t think we’re missing florid Cushing.”
However, Dr. Wardlaw said, it’s probably worthwhile to detect even milder hypercortisolism because it could still have long-term damaging effects, including osteoporosis, muscle weakness, glucose intolerance, and frailty. “You could do something about it and normalize it if you found it. I think that would be the reason to do it.”