Other forms of diabetes

Question 1

What is MODY? When is it typically diagnosed?

Answer 1

MODY is a rare form of diabetes which is different from both type 1 and type 2 diabetes, and runs strongly in families.
MODY is caused by a mutation in a single gene (HNF) altering beta cell function. If a parent has this gene mutation, any child they have, has a 50% chance of inheriting it from them.

It is typically diagnosed before 25.

Question 2

What are some of the genetic mutations which occur in MODY?

Answer 2

Hepatic nuclear factor 1A mutation (MODY3) - sensitive to sulponylureas for 80% do not need insulin treatment

Hepatic nuclear factor 4! (MODY1) - usually in non obese children, sensitive to sulfonylureas, babies usually very heavy birth weight and usually presents with neonatal hypoglycaemia.

Glucose kinase mutation (MODY2) - GCK is the glucose sensor of beta cells and controls release of insulin - symptoms are mild and don’t require treatment.

Question 3

What is maternally inherited diabetes and deafness?

Answer 3

Mutation in mitochondrial DNA causing loss of beta cell mass.
Similar presentation to T2DM

Question 4

Name some exocrine causes of diabetes

Answer 4

Inflammation of pancreas and chronic pancreatitis in alcoholics (damages exocrine function of pancreas and alters secretion of insulin and glucagon)

Hereditary hemochromatosis

• Excessive intestinal absorption of iron and therefore, build up of iron depostied in liver, pancreas, pituitary, heart and parathyroid.
• Autosomal recessive condition
• Presents with triad: cirrhosis, diabetes and bronzed hyperpigmentation.
• Insulin treatment most of the time

Pancreatic neoplasia

• Common cause of cancer death
• Required insulin
• Prone to hypoglycaemia due to loss of glucagon
• Frequent, small meals and enzyme replacement needed

Cystic fibrosis

• Mutation in CFTR gene on chromosome 7 (regulates chloride secretion)
• Viscous secretions build up. in lungs, pancreas etc whihc stop the pancreas function
• Affects 25-50% of adults with CF
• Ketosis rare as they still have exocrine fx
• Insulin needed and this actually improves QOL for CF patients as a lot of the time they are underweight, and insulin increases their weight, lung function and lowers their infection rate.

Question 5

What are some endocrine causes of diabetes?

Answer 5

Acromegaly

• Excessive secretion of GH
• Behave similar to T2DM
• Insulin resistance rises impairing insulin action in liver and peripheral tissues

Cushings syndrome

• Glucocorticoid excess causes increased insulin resistance and reduced glucose uptake into tissues
• Treatment is to remove excess glucocorticoid

Pheochromocytoma

• Tumours that produce extra catecholamines (epinephrine excess)
• Increased gluconeogenesis
• Decreased glucose uptake
• Treat by ressecting tumour

Question 6

How are glucocorticoids associated with diabetes?

Answer 6

They increase insulin resistance