GLP-1 medications are all you read about in the medical literature (journals, newsletters) these days. The benefits of better control of diabetes and 20%-25% weight loss are hard to dispute. Eli Lilly and Co. in Indianapolis had the brilliant foresight to realize these two functions early on and make note of the vast number of people who would be desirous of these effects. Instead of putting all their eggs in one basket, they marketed the same drug, Tirzepatide, as two separate drugs. Despite using Tirzepatide for both, Lilly’s drug indicated for diabetes was called Mounjaro, and their weight loss drug was called Zepbound. PURE MARKETING GENIUS!
There are two GLP-1 drugs that dominate the market, today. The other not mentioned above is semaglutide, or as the catchy advertisement goes, “Oh oh oh, Ozempic, oh ohooo!” Thus far the significant weight loss generated by GLP-1’s has been the major focus for users even though diabetes control was the original indication. Eli Lilly has again taken the spotlight away from semaglutide and is shining it right on tirzepatide.
What Lilly has done involves people diagnosed with type 2 diabetes for four years or less. They have shown that tirzepatide (Mounjaro) affected two very important functions that cause type 2 diabetes. These two functions are: beta-cell function and insulin sensitivity. Their SURPASS-EARLY study showed better blood sugar control with tirzepatide compared to a non-GLP-1 treatment regimen.
Beta cells are the cells in the pancreas located in the Islets of Langerhans, where insulin is produced and released. When the Beta cells fail, insulin production is reduced, and blood sugar rises. Tirzepatide was proven to be superior to semaglutide in improving Beta cell function. It improves the Beta cells’ ability to respond to high blood sugars and react by increasing insulin secretion.
Insulin sensitivity is the other measure tirzepatide improved. Type 2 diabetics develop insulin resistance. The insulin produced isn’t as responsive to lowering high blood sugars. Tirzepatide was shown to improve insulin’s sensitivity, or its ability to respond to high blood sugars.
As a secondary effect of better Beta cell function and increased insulin sensitivity, tirzepatide significantly lowered A1C levels (to 5.56%), resulted in better weight loss (15.8 kg or 35 lbs.), and normalized blood sugar levels, all over a two year period. Patients on tirzepatide achieved A1C levels of 6.5% or below in 91% of patients. These improvements all were demonstrated in patients who had been diabetic for 4 years or less, ie. new diabetics. The purpose of the study was to show that Mounjaro should be used early in the course of type 2 diabetes because the Beta cells are more responsive early than later in the disease course.
Eli Lilly is doing their best to market tirzepatide and doing a bang up job of it. Their profits are phenomenal. Their stock price today was $1169.00. When I looked at it several months ago it was $790.00. And Lilly’s market valuation now exceeds $1 Trillion. Well, good for Lilly, all my former patients who are Lilly retirees, people who own Lilly stock, and patients who can afford to buy Zepbound and Mounjaro.
Reference: Tucker M. Tirzepatide Ups Beta-Cell Function, Insulin Sensitivity in Early Type 2 Diabetes. medscape.com 2026 September 29.
