Study Updates Prevalence of Cushing’s Syndrome Diagnoses in Sweden

In the modern era, three new cases of Cushing’s syndrome are being diagnosed annually per one million inhabitants, according to results from a study conducted in a region of Sweden.

Also, more patients with ectopic Cushing’s syndrome are being diagnosed compared to prior reports, which researchers attribute to an increased awareness that some malignant tumors may cause a rise in cortisol levels.

The study “The incidence of endogenous Cushing’s syndrome in the modern era” was published in the journal Clinical Endocrinology.

Cushing syndrome is characterized by high levels of the hormone cortisol in your body. It is composed of several subtypes, the most common of which is Cushing’s disease, in which a tumor of the pituitary gland produces too much of the adrenocorticotropic hormone (ACTH), stimulating cortisol production.

There also are other other subtypes of Cushing’s syndrome, including tumors outside of the pituitary gland (ectopic tumors) that produce ACTH, and adrenal disease, in which a tumor in the adrenal glands (which produce cortisol) is responsible for the elevated cortisol levels.

There is a lack of epidemiological and population-based studies of Cushing’s syndrome. As a result, there is a limited knowledge about the incidence of subtypes of this condition. This is especially true for the less-common subtypes of Cushing’s syndrome.

A group of Swedish researchers set out to determine the incidence of Cushing’s syndrome in a group of patients from the Västra Götaland County in Sweden from 2002 to 2017.

During that period, there were 82 patients diagnosed with Cushing’s syndrome in the region. Among them, 39 patients (48%) had Cushing’s disease, 21 (26%) had an ectopic ACTH-producing tumor, 17 (21%) had  benign adrenal disease, and five (6%) had cortisol-producing adrenocortical carcinoma (adrenal cancer).

Among the 21 patients with an ectopic ACTH-producing tumor, nine (43%) had a lung tumor, four had a neuroendocrine pancreatic tumor, and five had an occult (unable to locate) tumor.

Overall, the annual incidence of endogenous Cushing’s syndrome in that period was 3.2 cases per one million inhabitants. Regarding each subtype, the incidence of Cushing’s disease was 1.5 cases per million per year, ectopic Cushing’s syndrome was 0.8 cases per million per year, benign adrenal Cushing’s syndrome was 0.7 cases per million per year, and adrenocortical carcinoma was 0.2 cases per million per year.

While the incidence of Cushing’s disease and cortisol-producing adrenal disease in this study is in line with most previous studies, there is a significantly higher proportion of patients with ectopic adenomas.

“The reason for this is unclear although increased awareness of [high cortisol levels] in patients with malignant tumours in the modern era is a possible explanation,” investigators wrote.

“Approximately three new cases of endogenous CS [Cushing’s syndrome], per one million inhabitants, were diagnosed annually in the Västra Götaland County in Sweden between 2002 and 2017. Half of the CS cases were caused by CD [Cushing’s disease], one-fourth by an ectopic ACTH-producing tumour and one-fourth by adrenal disease,” they concluded.

“Further research, preferably on larger populations in different geographical areas, is necessary to establish the true incidence and prevalence rates of endogenous CS,” investigators added.