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Study breakdown

Tirzepatide dramatically reduced insulin needs in rare MODY diabetes by increasing C-peptide 3-fold

RPEP-136992025Sue, Mihiro; Watanabe, Mayu; Inoue, Ayumi; Katayama, Akihiro; Teshigawara, Sanae; Matsushita, Yuichi; Takeda, Masaya; Iseda, Izumi; Eguchi, Jun; Hida, Kazuyuki
evidence
The takeaway

First case of tirzepatide in MODY (HNF1B mutation): fasting C-peptide tripled from 0.36 to 1.09 ng/mL, total insulin reduced from 88 to 4 units/day, and glimepiride discontinued in a 26-year-old with 15-year diabetes history.

88 → 4 units insulin

Tirzepatide tripled C-peptide and reduced insulin needs 22-fold in the first MODY case treated with this dual GIP/GLP-1 agonist

What the researchers found

C-peptide: 0.36→1.09 ng/mL (3x increase). Insulin: 88→4 units/day. Glimepiride discontinued. HNF1B p.Glu105Lys MODY. 26-year-old, 15-year diabetes duration.

Why it matters

MODY is characterized by impaired insulin secretion, and this case shows tirzepatide can dramatically restore it. This could change management of MODY subtypes that retain some beta-cell function.

How the study worked

Single case report of tirzepatide in MODY with HNF1B mutation.

What this study cannot tell us

Single case. Cannot generalize to all MODY subtypes. HNF1B MODY is rare. Long-term durability unknown.

How to read the evidence

Single case report—lowest evidence but first-ever in MODY.

When this study was published

Published in 2025.

The bigger picture

MODY is often treated with insulin due to impaired secretion. If tirzepatide can rescue beta-cell function in genetic diabetes, it expands the drug's potential far beyond type 2 diabetes.

Questions still open

  • Is the C-peptide improvement durable long-term?
  • Which MODY subtypes respond best to tirzepatide?
  • Does GIP or GLP-1 receptor activation drive the beta-cell rescue?

Common questions

What is MODY?
Maturity-onset diabetes of the young (MODY) is a genetic form of diabetes caused by single gene mutations. Unlike type 1 or type 2, it is inherited and usually appears before age 25. Treatment typically requires insulin because the beta-cells do not produce enough.
How did tirzepatide help with MODY?
Remarkably, tirzepatide tripled the patient's insulin production (C-peptide) and reduced her insulin injections from 88 to just 4 units daily. This suggests the dual GIP/GLP-1 mechanism can "wake up" beta-cells that genetic mutations have partially silenced.

Read the original research

Maturity-Onset Diabetes of the Young (MODY) With HNF1B p.Glu105Lys Mutation Achieving Significant Insulin Reduction on Tirzepatide: A Case Report.

Clinical case reports, 13(2), e70173

View on PubMed ↗Publisher’s paper ↗

Citation

Sue, Mihiro; Watanabe, Mayu; Inoue, Ayumi; Katayama, Akihiro; Teshigawara, Sanae; Matsushita, Yuichi; Takeda, Masaya; Iseda, Izumi; Eguchi, Jun; Hida, Kazuyuki. (2025). Maturity-Onset Diabetes of the Young (MODY) With HNF1B p.Glu105Lys Mutation Achieving Significant Insulin Reduction on Tirzepatide: A Case Report.. Clinical case reports, 13(2), e70173. https://doi.org/10.1002/ccr3.70173