The prevalence of Addison’s disease, mostly due to primary adrenal failure due to autoimmune adrenalitis, is 93– 140 per million while secondary insufficiency, mostly due to hypothalamic– pituitary tumours, has a prevalence of 125– 280 per million. The overall prevalence of adrenal insufficiency is 5 in 10 000 population; on average, three of those suffer from secondary adrenal insufficiency, one from primary adrenal insufficiency due to autoimmune adrenalitis, and one from congenital adrenal hyperplasia.
Primary Adrenal Insufficiency
According to recent studies, chronic primary adrenal insufficiency has a prevalence of 93 to 140 per million and an incidence of 4.7 to 6.2 per million in Caucasian populations. These numbers are considerably higher than reported earlier, despite a continuous decline in tuberculous adrenalitis in the developed world, and suggest an increasing incidence of autoimmune adrenalitis. The age at diagnosis peaks in the fourth decade of life, with women more frequently affected. For details on the rare inborn causes of primary adrenal insufficiency, please see Chapters 5.8.1 and 5.9.1.
Secondary Adrenal Insufficiency
Secondary adrenal insufficiency has an estimated prevalence of 150 to 280 per million. Again, women are more frequently affected and age at diagnosis peaks in the sixth decade.
It has been suggested that therapeutic glucocorticoid administration is the most common cause of adrenal insufficiency, as exogenous glucocorticoids induce atrophy of both pituitary corticotroph and adrenocortical cells. However, iatrogenic adrenal insufficiency only becomes potentially relevant during or after glucocorticoid withdrawal. As iatrogenic adrenal insufficiency is transient in the majority of cases it can be suspected that the prevalence of permanent iatrogenic adrenal insufficiency is clearly lower than that of endogenous adrenal insufficiency.
