From one question to a medical revolution: The Saul Hertz legacy behind modern theranostics

Some of medicine’s most consequential breakthroughs do not begin in operating theatres, laboratories or with expensive machines. Sometimes, they begin with a question.

In 1936, Dr. Saul Hertz, a physician at Massachusetts General Hospital, asked one that would eventually help reshape the treatment of disease: Could radioactive iodine be used to study the physiology of the thyroid?

The question was deceptively simple.

The answer would require medicine to cross paths with nuclear physics—and would ultimately help establish a principle that now sits at the heart of precision medicine: use a biological target to find disease, and then use that same target to treat it.

Hertz recognised something fundamental about the thyroid. The gland naturally absorbs iodine. If iodine could be made radioactive, he reasoned, it might be possible to follow its movement in the body and, potentially, deliver radiation directly to abnormal thyroid tissue.

But there was a problem.

Could iodine actually be made radioactive artificially?

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That question brought Hertz into collaboration with physicist Arthur Roberts.

Together, they moved from hypothesis to experimentation, laying the groundwork for a medical application that was then largely uncharted territory.

By 1941, Hertz had used radioactive iodine in the treatment of patients with thyroid disease.

The significance of the work extended far beyond the thyroid.

Where medicine met nuclear physics

Hertz’s pioneering work demonstrated a powerful concept: radioactive substances could potentially be used to target disease from within the body.

That idea helped lay the foundation for nuclear medicine and, decades later, for the evolution of radionuclide therapy and theranostics—an approach in which molecular targets can be exploited for both diagnosis and treatment.

In modern theranostics, physicians can identify a biological target, use a radiopharmaceutical to visualise it and, where appropriate, employ a related radioactive treatment to attack the targeted disease.

The underlying philosophy is remarkably close to the question Hertz was exploring almost a century ago: Can the biology of a disease be used to guide its detection and treatment?

Today, that concept is being applied in increasingly sophisticated ways across nuclear medicine, molecular imaging and precision oncology.

What began with thyroid physiology has become part of a much broader effort to make cancer treatment more targeted and personalised.

A legacy preserved across generations

The scientific legacy of Saul Hertz has also survived through the efforts of his family.

Decades after his pioneering work, his daughter, Barbara Hertz, has devoted considerable effort to preserving and sharing her father’s history through the Dr. Saul Hertz Archives.

The archives serve as a repository for records and materials connected to Hertz’s work, helping ensure that the history behind the development of radioiodine therapy remains accessible to researchers, physicians and the wider medical community.

Barbara Hertz has also contributed to scholarly efforts documenting her father’s role in the development of radioiodine therapy, keeping alive a story that might otherwise have become buried beneath decades of subsequent scientific advances.

That preservation matters because medical breakthroughs are often remembered through their outcomes while the questions, experiments and people behind them fade into history.

Why the Saul Hertz name matters today

The continuing relevance of Hertz’s work is being recognised through the Saul Hertz Best Abstract Award, introduced at the International Symposium on Radiopharmaceutical Therapy 2026.

The award honours outstanding work by early-career investigators working in areas including nuclear medicine, radiopharmaceutical therapy, molecular imaging and precision oncology.

In many respects, the award represents a bridge between generations.

The young scientists being recognised today are working with technologies, molecular targets and therapeutic strategies that Hertz could scarcely have imagined in 1936. Yet the scientific philosophy connecting their work to his remains strikingly familiar.

Ask the right biological question.

Find a way to exploit what the body naturally does.

Turn that understanding into a tool for diagnosis.

Then ask whether the same pathway can be used to deliver treatment.

That is the intellectual journey from radioiodine to modern theranostics.

From 1936 to the future of precision medicine

The story of Saul Hertz is therefore more than a historical account of an early nuclear medicine experiment.

It is a story about scientific curiosity—and about what can happen when disciplines that appear unrelated are brought together.

Hertz was a physician asking questions that required the expertise of a physicist. Their collaboration helped demonstrate that radiation could be harnessed through the body’s own biological processes.

Nearly 90 years later, scientists are still pursuing variations of that same idea.

Radiopharmaceutical therapy is emerging as an important component of precision oncology, with researchers investigating increasingly selective ways of delivering radiation to diseased cells while limiting exposure to healthy tissue.

The technology has changed. The diseases being targeted have expanded. The molecular understanding of cancer has become vastly more sophisticated.

But the fundamental ambition remains remarkably consistent.

Find the target. See the target. Treat the target.

That is the enduring significance of Saul Hertz.

His greatest contribution may not simply have been the treatment of thyroid disease with radioactive iodine. It was the scientific door he helped open—a door through which nuclear physics could become a tool of medicine and, ultimately, a foundation for a new generation of targeted therapies.

From a question asked in 1936 to a rapidly evolving field transforming cancer care today, the journey of theranostics demonstrates the extraordinary reach of a good scientific question.

And that is why, decades later, the name Saul Hertz continues to matter.