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# Maturity-onset diabetes of the young (MODY)

Diabetes caused by a single dominant gene, often mistaken for type 1 or type 2; the exact gene changes treatment.

Updated Nov 13, 2026

On this page

- The basics What it is
- Who gets it
- Causes
- Pathophysiology
- Classification

- Clinical Symptoms and signs
- Red flags
- Diagnosis
- Complications
- Prognosis

- Treatment Treatment

- Study Test yourself

- Connections Connections

## What it is

A group of monogenic forms of diabetes with autosomal dominant inheritance, caused by variants in genes that control insulin secretion by the β cell.

See it in 3D

- [Pancreas](https://durgical.com/en/anatomy/pancreas/)
- [Kidneys](https://durgical.com/en/anatomy/kidney/)

## Who gets it

About 1–2 % of all diabetes; most cases are not diagnosed.

## Causes

- Heterozygous variants in GCK, HNF1A, HNF4A, HNF1B and other β-cell genes
- Autosomal dominant inheritance: diabetes in several generations

## Pathophysiology

Glucokinase is the β cell's glucose sensor: GCK variants reset the glucose level at which insulin is released, giving mild, stable fasting hyperglycaemia. HNF1A and HNF4A are transcription factors needed for β-cell function; their loss causes progressive insulin deficiency. HNF1B variants also affect the [kidneys](https://durgical.com/en/anatomy/kidney/) and genital tract.

## Classification

- GCK-MODY: mild, stable fasting hyperglycaemia from birth, usually needing no treatment
- HNF1A-MODY: progressive diabetes, very sensitive to sulfonylureas, glucose in urine at modest blood glucose
- HNF4A-MODY: similar to HNF1A, with large birth weight and newborn hypoglycaemia
- HNF1B-MODY: diabetes with renal cysts and genital anomalies

## Symptoms and signs

- Diabetes diagnosed in youth or young adulthood, often by chance
- Not obese, without signs of insulin resistance
- Strong family history across generations
- Little tendency to ketoacidosis

## Red flags

- Hyperglycaemia during pregnancy in a woman with known GCK-MODY needs specialist advice

## Diagnosis

**Clinical**
Suspect when diabetes appears young in a lean person with a parent affected, negative islet autoantibodies and preserved C-peptide years after diagnosis.

**Tests**
Genetic testing of MODY genes; islet autoantibodies negative; C-peptide preserved.

**Imaging**
Renal ultrasound in suspected HNF1B-MODY.

## Treatment

**Follow-up**
GCK-MODY usually needs no glucose-lowering treatment outside pregnancy.

**Medical**
HNF1A- and HNF4A-MODY respond well to sulfonylureas, often allowing insulin to be stopped.

**Lifestyle**
Healthy diet and activity as in other diabetes.

## Complications

- Microvascular complications in progressive forms if poorly controlled
- Misdiagnosis leading to unnecessary insulin

## Prognosis

Good with the right diagnosis; GCK-MODY rarely causes complications.

## Test yourself

Think of the answer, then tap the question to see it.

## Which MODY usually needs no treatment, and why?

GCK-MODY: glucokinase variants only reset the glucose threshold for insulin release, causing mild, stable hyperglycaemia.

## Which drug class works especially well in HNF1A-MODY?

Sulfonylureas.

## Which findings suggest MODY rather than type 1 diabetes?

Negative islet autoantibodies, preserved C-peptide and dominant inheritance across generations.

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## Connections

## Related conditions 2

- [Type 1 diabetes mellitus](https://durgical.com/en/conditions/type-1-diabetes-mellitus/)
- [Type 2 diabetes mellitus](https://durgical.com/en/conditions/type-2-diabetes-mellitus/)

Educational information, not medical advice. For any symptom, see a health professional.

Sources: [Maturity-onset diabetes of the young: MedlinePlus Genetics](https://medlineplus.gov/genetics/condition/maturity-onset-diabetes-of-the-young/) (MedlinePlus, US National Library of Medicine, 2026); [GCK gene: MedlinePlus Genetics](https://medlineplus.gov/genetics/gene/gck/) (MedlinePlus, US National Library of Medicine, 2026); [HNF1A gene: MedlinePlus Genetics](https://medlineplus.gov/genetics/gene/hnf1a/) (MedlinePlus, US National Library of Medicine, 2026).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/conditions/maturity-onset-diabetes-of-the-young/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/conditions/maturity-onset-diabetes-of-the-young/