Insulin, 1922: A Physician’s Read on the First Peptide Medicine
By Andres Zuleta, MD
The first clinical use of insulin is usually told as a triumph. Read the 1922 Canadian Medical Association Journal paper and the University of Toronto records, and it is also a story about a failed first attempt, a purification problem, and a treatment whose main risk we still manage today.
The case
Leonard Thompson, 14, was admitted to Toronto General Hospital on December 2, 1921, weighing 65 pounds on a diet of about 450 calories a day. On January 11, 1922, he received a pancreas extract prepared by Banting and Best. Blood sugar fell by about a quarter, without clinical benefit, and an abscess formed at the injection site. On January 23, daily injections of James Collip's purified extract began. Blood sugar normalized within a day, urinary sugar fell from well over 100 grams a day to between 7.5 and 45 grams on treatment days, and ketonuria cleared. All seven patients in the first report improved.
What it proved, and what it did not
It proved that a pancreatic extract could reverse the acute metabolic state of type 1 diabetes in humans, and that purity was the difference between failure and success. It did not provide a cure: when injections stopped for ten days that February, glycosuria returned. The authors warned of severe toxic reactions with impure batches. The 1923 Nobel Prize named Banting and Macleod; Best and Collip were not named.
The second patient everyone remembers
Elizabeth Hughes arrived in August 1922, age 14, 45 pounds, after a starvation diet since 1919. Five weeks of insulin added ten pounds. She learned to inject herself, went to college, and lived to 73. Leonard Thompson lived 13 more years and died in 1935, at 27, of pneumonia and complications of diabetes.
The line to today
Insulin is a 51-amino acid peptide hormone, and it was the first peptide medicine; more than 80 peptide drugs have followed. DCCT (1993, 1,441 participants) showed a 76 percent reduction in new retinopathy risk with intensive therapy, with 2 to 3 times more severe hypoglycemia as the tradeoff. Teplizumab (FDA, 2022) delayed stage 3 diagnosis by about two years in 76 high-risk participants. A small 2025 trial of stem cell-derived islets reported insulin independence at one year in 10 of 12 participants, with immunosuppression and serious adverse events still unresolved.
The practical part
Insulin sensitivity is modifiable day to day. One night of four hours of sleep reduced insulin sensitivity by about 25 percent in nine healthy adults (Donga et al., 2010), and light walking breaks during prolonged sitting lowered postprandial glucose and insulin across seven one-day trials (Buffey et al., 2022).
For the patient-friendly version, read my full post on the ThriveMed blog: https://www.thrivemed.us/thrivecityblog/first-insulin-patient-leonard-thompson-1922.
Sources: Can Med Assoc J 1922 (PMC1524425); nobelprize.org; NEJM 1993, 2019, 2025; J Clin Endocrinol Metab 2010; Sports Med 2022. Educational only, not medical advice.