United States
Cushing syndrome is a rare disorder, with 90% of cases occurring during adulthood. Overall incidence is estimated to be 2 new cases per million population per year. Incidence in children is estimated at approximately 0.2 cases per million population per year.
The National Cancer Institute (NCI) estimates the incidence of adrenal cortical carcinoma as 2 cases per million population per year. Pituitary causes of Cushing disease are 5-6 times more common than adrenal causes.
Prevalence of exogenous Cushing syndrome depends on the frequency and spectrum of medical conditions requiring glucocorticoid treatment in a given population. Considerable variation in this frequency is observed in populations of different cultural and ethnic backgrounds.
International
In certain regions of the world (eg, Japan, Brazil), adrenal tumors are more frequently observed. Whether this and other aberrations are due to a genetically determined founder effect in a small subset of the population or whether environmental factors may be acting to increase patient risk is unknown.
Mortality/Morbidity
As a result of the multiple adverse effects of chronic glucocorticoid excess, both endogenous and exogenous Cushing syndrome are associated with significant morbidity. Untreated, they are also associated with an increased risk of premature death. Specific information about the effects of glucocorticoids on different systems is summarized in Table 2.
Sex
Endogenous Cushing syndrome of pituitary etiology is more prevalent in women than in men, with a female-to-male ratio of 9:1. Females are 8 times more likely than males to develop an ACTH-secreting pituitary adenoma and 3 times more likely to develop a cortisol-secreting adrenal tumor.
Age
Onset of endogenous Cushing syndrome of pituitary etiology occurs primarily in the third and fourth decades of life.