It was 1964, and Irwin Schatz, a young Detroit doctor with a penchant for flipping through medical journals, had come across a headline that stunned him. He reread it several times, convinced that he could not be interpreting it correctly.

But the title — “The Tuskegee Study of Untreated Syphilis: 30 years of Observation,” — didn’t change. Nor did its meaning.

“The message was unmistakable,” Schatz later said in an e-mail to the Hawaii news site Civil Beat. “These researchers had deliberately withheld treatment for this group of poor, uneducated, black sharecroppers from Mississippi with late syphilis in order to document what eventually might happen to them. I became incensed. How could physicians, who were trained first and foremost to do no harm, deliberately withhold curative treatment so they could understand the natural history of syphilis?”

Just four years out of medical school and with no other means of recourse, Schatz wrote a succinct, scathing letter to the study’s authors.

“I am utterly astounded by the fact that physicians allow patients with a potentially fatal disease to remain untreated when effective therapy is available,” the 1965 letter read. “I assume you feel that the information which is extracted from observation of this untreated group is worth their sacrifice. If this is the case, then I suggest the United States Public Health Service and those physicians associated with it in this study need to re-evaluate their moral judgments in this regard.”

Anne R. Yobs, one of the authors of the now-infamous study, received the letter. She wrote a brief memo to her supervisor — “This is the first letter of this type we have received. I do not plan to answer this letter” — stapled it to the top of the letter, and that was that.

It would be almost two more years before another letter was written questioning the study’s ethics and eight before criticism was widely reported. In the meantime, Schatz’s missive languished in a Centers for Disease Control archive.

Schatz, who died at his home in Honolulu this month at age 83, according to the Honolulu Star Adviser, never made much of the fact that he was the Tuskegee experiment’s first, loneliest critic.

“To this day, you have to prod him to mention it,” Schatz’s son, U.S. Sen. Brian Schatz (D-Hawaii) told Pomona College Magazine in 2013. “His style is that you just do the right thing and move on, then you do the right thing again and just move on.”

But Schatz’s letter was uncovered by a Freedom of Information Act request from a Wall Street Journal reporter in 1972, the same year that the study was first reported with help from a health service employee turned whistle-blower, Peter Buxtun. It helped launch a national debate about medical ethics.

The Tuskegee study began in 1932, when there was no known treatment for syphilis. But even after penicillin became the standard treatment for the disease in 1947, the 399 participants who had syphilis — all of them black men, most of them poor and poorly educated — weren’t given the medicine. None of the men were aware they had the illness. Instead, researchers told the men they were being treated for “bad blood,” a violation of the medical principle of “informed consent.”

At least seven participants died as a direct result of syphilis, according to a 1972 New York Times report, and several more unwittingly passed on the disease to women and children. Later that year, the CDC issued an order calling for the termination of the study, and the 74 still-living participants soon began treatment for the disease.

The study raised questions about racial discrimination and patients’ rights, and many critics compared it to Nazi medical experiments conducted during World War II. The backlash led to creation of the National Commission for the Protection of Human Subjects of Biomedical and Behavioral Research, which set the first-ever guidelines for human research. It also helped create the Tuskegee Health Benefit Program, which provided medical benefits and services for participants, their wives and their children.

In the meantime, Schatz remained a little-known heart researcher. The son of two restaurant owners from Winnipeg, Manitoba, he had undergraduate and medical degrees from the University of Manitoba and a fellowship at the Mayo Clinic. In the early 1960s he volunteered on the hospital ship SS Hope, according to the Honolulu Star-Advertiser, then held positions at various U.S. hospitals. In 1975, he joined the faculty of the University of Hawaii, where he eventually became chairman of the department of medicine.

And in 2009, Schatz’s role as the Tuskegee study’s first opponent was formally recognized when he was named a “medical hero” by the Mayo Clinic.

Schatz “was a young physician at the time, and criticizing an investigation which was overseen by some of the leading figures in the American Public Health Service was an action that was, to say the very least, potentially harmful to his career,” David Robertson, who nominated Schatz, wrote.

Schatz is survived by his sons, Jacob, Edward, Stephen and Brian; nine grandchildren; and a sister, Bea Berger.