Addison’s disease, also known as primary adrenal insufficiency, is relatively uncommon disorder affecting about 8,400 people in the UK. It occurs when the two adrenal glands situated atop of the kidneys are damaged giving rise to a deficiency in two essential steroid hormones (cortisol and aldosterone) due in most cases to an autoimmune response. Tending to present first during childhood, it can be indicated by, for example, muscle weakness and increased thirst. Treatment by means of corticosteroids can give rise to asthma. It is an X-linked trait and thus inherited from mother to child. Perhaps the most famous sufferer of the disease was John F. Kennedy.