At the end of the 19th century, surgery was still dangerous, and many doctors had little understanding of what happened to patients in the long term. Operations were often followed by infection, bleeding or unexplained decline. The thyroid gland was known mainly because it enlarged in conditions such as goitre, but its role in the body remained unclear. Removing it was seen largely as a technical task, with not much attention paid to its broader effects.
Kocher changed this way of thinking by showing that the thyroid was not expendable but essential for normal physical and mental function. His work helped shift surgery away from purely mechanical intervention towards a more physiological understanding of the body.
By closely observing patients before and after thyroid surgery, Kocher noticed that those who had the entire gland removed often developed serious physical and mental problems. These long-term effects were impossible to ignore. His observations forced surgeons to rethink their approach, moving the focus from simply removing diseased tissue to preserving normal bodily function wherever possible.
Early scientific formation
Emil Theodor Kocher was born on August 25, 1841, in Bern, Switzerland. He studied medicine at the University of Bern and, after completing his training, travelled to several leading medical centres in Europe, including Berlin, London and Paris. There, he learned from prominent physicians and surgeons and was exposed to emerging ideas on antisepsis, precision surgery and anatomical accuracy.
These experiences strongly shaped his belief that surgery should be disciplined, exact and scientifically grounded. For Kocher, careful technique and cleanliness were central to patient survival.
Kocher later returned to Bern, where he was appointed professor of surgery and spent most of his professional life. He became known for his methodical and restrained approach, combining careful clinical observation with a strong sense of responsibility for patient outcomes. His surgical style emphasised gentle tissue handling, precise dissection and strict control of bleeding, helping to dramatically improve safety and reduce complications.
Understanding the thyroid’s role
Kocher’s most influential work came from his observations of patients who had undergone total thyroidectomy (surgical removal of the entire thyroid gland). He noticed that many developed fatigue, weight gain, slowed movement and cognitive decline symptoms that closely resemble what is now recognised as hypothyroidism.
He described this condition as cachexia strumipriva, clearly linking it to the complete removal of the thyroid gland. This insight was groundbreaking at a time when the idea of organs releasing internal chemical signals was still emerging. Kocher’s work provided some of the earliest clinical evidence that organs could influence the entire body through internal regulation, laying important groundwork for modern endocrinology.
Surgical innovation and safety
Kocher was also a technical innovator. He refined thyroid surgery to minimise bleeding and protect nearby nerves, particularly those affecting speech and breathing. Through careful technique and strict aseptic practices, he reduced mortality rates from thyroid surgery from extremely high levels to well below one percent.
As his understanding of thyroid function deepened, Kocher altered his surgical approach. Instead of routinely removing the entire gland, he advocated partial thyroidectomy whenever possible, preserving enough tissue to maintain normal physiological function. This marked a crucial shift from radical removal to function-preserving surgery.
Nobel recognition
The Nobel Committee awarded Kocher the 1909 Prize in Physiology or Medicine ‘for his work on the physiology, pathology and surgery of the thyroid gland.; The award recognised not a single experiment, but a sustained body of work that combined surgery, long-term patient observation and physiological insight.
His achievements helped establish surgery as a scientific discipline rooted in biological understanding rather than technical skill alone. Kocher demonstrated that successful treatment required knowing how organs function within the wider system of the body.
Impact on medicine and public health
Kocher’s findings reshaped the treatment of thyroid disorders worldwide. They influenced how conditions such as goitre, hypothyroidism and later hyperthyroidism were understood and managed, combining surgical care with emerging medical therapies.
Broadly, his work helped legitimise the concept of internal secretion, supporting the development of endocrinology as a distinct medical field. Modern hormone replacement therapies and diagnostic approaches to thyroid disease can be traced back to the principles he established.
Enduring legacy
Kocher was the first surgeon and the first Swiss citizen to receive a Nobel Prize in Physiology or Medicine. Many surgical instruments and techniques still bear his name today, including Kocher’s forceps, widely used to control bleeding, and the Kocher manoeuvre, a standard technique in abdominal surgery taught worldwide.
In Bern, his legacy is formally commemorated. Research institutes, academic prizes and public memorials including a park and a bronze bust near the university hospital — honour his contributions to medicine. Kocher also donated his Nobel Prize money to support scientific research, reflecting his lifelong commitment to medical education and discovery.
