“When your adrenal glands are overtaxed, a condition known as adrenal fatigue or adrenal exhaustion sets in, which in turn can set a cascade of disease processes into motion,” claims Joseph Mercola on his website.

“The theory of adrenal fatigue—which was coined by chiropractor James Wilson in the late ’90s—is that overexertion of the adrenal glands as they continuously pump out the stress hormone cortisol eventually leads the adrenals to burn out, resulting in an inability to respond to stress,” explains Rashmi Mullur, an endocrinologist and assistant professor of medicine at UCLA.

Adrenal fatigue affects up to 80 percent of American adults at some point during their lifetime, says Wilson’s book, Adrenal Fatigue: The 21st Century Stress Syndrome. It’s responsible for salty and sweet cravings, being tired for no reason, and more, he claims.

Only one problem, notes Mullur: “No matter how much stress we’re under, our adrenal glands won’t burn out.”

The pituitary (a pea-sized gland in the brain) tells the adrenal glands to produce cortisol. In turn, “cortisol acts as a messenger from the adrenals, and tells the pituitary, ‘We’re good. We’ve made enough hormone. You don’t need to stimulate us any more, ’” Mullur explains. “It’s a self-regulating system.”

The processes that control cortisol production can break down, for example in people who have Addison’s disease (when the adrenals don’t make enough cortisol) or Cushing’s disease (when they make too much).

“But I can test for those diseases, and it’s a very clear ‘Yes, you have this’ or ‘No,  you don’t,’” says Mullur.

So why do some people feel so exhausted? Other problems—like thyroid disease, depression, sleep apnea, past trauma, anemia, or stress—could be the culprit.

As for supplements that provide “adrenal support,” don’t bother, says Mullur. When researchers bought a dozen popular ones online, they found thyroid hormone in all 12 and at least one steroid hormone in seven. None of the hormones—it’s illegal for them to be in supplements—were listed on the labels.

Those ingredients could influence hormonal pathways in unpredictable ways, Mullur points out. What’s more, they could interfere with hormone tests, making it harder for your doctor to diagnose problems.

The bottom line 

“The term adrenal fatigue doesn’t capture what people are experiencing, because it’s not an adrenal issue,” says Mullur. “But the burnout and exhaustion are absolutely real. If we doctors dig a little deeper to get to the root cause of those issues, we’re more likely to help patients.”