Cushing Syndrome

A Factory With a Broken Thermostat

Imagine a factory that makes a powerful chemical (cortisol) that the whole city depends on. Normally, a thermostat in the main office (hypothalamus) checks the city's supply. When supply runs low, the thermostat sends a message to the factory manager (pituitary) who sends workers (ACTH messengers) to the production floor (adrenal glands) to turn on the machines and make more. As supply builds up, the thermostat senses it and tells the manager to slow down—keeping the city perfectly supplied, 24 hours a day. But in Cushing syndrome, the thermostat breaks in one of four ways: the manager's brain tumor ignores the high-supply signal and keeps ordering production (Cushing disease), a rogue factory elsewhere in the city starts making the chemical without any thermostat (ectopic ACTH), the production floor machines turn on by themselves and ignore the shutdown order (adrenal tumor), or the city starts dumping in that same chemical from outside pills (exogenous steroids). In every case, the city is flooded with ten times the normal amount, day and night, and every building, street, and person in the city starts obeying the too-loud signal—wearing out, breaking down, and slowly failing because they cannot adapt to the wrong orders.