At age 30, Stephen Hopkins was back in the Army for a second time. After serving as an enlisted soldier from 1991 to 1995, he returned as an officer in 2000. He was a man who routinely maxed fitness tests and endured physical hardship while deployed to rural locales in Afghanistan. Selected for Special Forces training, Hopkins tackled the demanding courses with gusto, later returning to combat for a total of seven deployments. He had a job he loved and excelled at, and his star was ascending.

But in 2005, Hopkins began experiencing wild swings in blood pressure. And he had other symptoms: crippling nausea, constant dizziness, a skyrocketing heart rate. He was given a diagnosis of common high blood pressure, and for a while he felt better by keeping himself on a high dose of a medication for that condition. He was on deployment in Afghanistan when the nausea returned, with migraine symptoms, abnormal thirst and muddled thinking. Medical tests were inconclusive, leading military doctors and commanders to suspect depression, post-traumatic stress disorder or, worse, “malingering” — the medical term for soldiers who feign sickness to shirk duty.

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“‘Malingering’? I was offended,” said Hopkins, who retired in 2017 as a major and now lives in Fort Washington, Md. “I was seeking medical care so I could figure out how to stay in the Army, not get out.” He was sent back to the United States in the summer of 2012 and was getting ready to attend a training course when he collapsed one day in a parking lot. His parents drove him to Walter Reed National Military Medical Center in Maryland, where he was seen by Capt. Kevin Dorrance, then the facility’s chief of internal medicine. Dorrance investigated a wide range of possible factors, including endocrine conditions, PTSD and various types of toxic exposures. A series of tests increasingly pointed toward lead, but chronic lead poisoning — from repeated exposures months or years in the past, rather than from a recent, short-term exposure — cannot be definitively identified by blood tests.

Dorrance sent Hopkins to Mount Sinai Medical Center in New York for an X-ray fluorescence (XRF) test, a procedure to measure the level of lead in his bones. They were riddled with it: His tibia registered more than two and a half times the level expected in an average American his age, then 42. With that test, Hopkins became the first of 38 service members from 2012 to today tested at Mount Sinai for chronic lead poisoning. Of those, a dozen have measured bone lead levels higher than what is considered normal, including four with almost twice the expected amount. Dozens of other service members have gone to the Cleveland Clinic’s Center for Functional Medicine in Ohio to be treated for lead and other types of metal poisoning. While the number of affected soldiers is small, the diagnosis can be life-changing to these troops, who for years have wrestled with unexplained symptoms that mimic traumatic brain injury or PTSD, including impaired concentration, anger, anxiety and impulsivity, as well as physical manifestations like tremors, high blood pressure, low sperm count and peripheral neuropathy.