Diabetes Mellitus

Diabetes mellitus (DM) is a disease caused by deficiency or diminished effectiveness of endogenous insulin. It is characterized by hyperglycaemia, deranged metabolism and sequelae predominantly affecting the vasculature.
Life expectancy is reduced by 15 years in Type 1 diabetes; 5-7 years in Type 2 diabetes.
93 points are available for diabetes care in the QOF.

QOF data suggests that there are 1,766,391 patients registered as diabetic in England.
This gives a prevalence of 3.55%.¹
Prevalence models suggest the true prevalence is closer to 4.67%.²
The incidence of diabetes is increasing in all age groups. Type 1 diabetes is increasing in children (especially <5 years), and type 2 diabetes is increasing particularly in black and minority ethnic groups.

Risk Factors

People of South Asian, African and African-Caribbean and Middle-Eastern descent are at greater risk of type 2 diabetes, compared with the white population.
People who are obese, are inactive or have a family history are also at increased risk of type 2 diabetes.

• Gestational Diabetes and impaired glucose tolerance³
• Drugs: steroids and thiazides
• Pancreatic disease: acute and chronic pancreatitis (including surgery if 90% pancreas removed), haemochromatosis, cystic fibrosis.
• Endocrine disease: Cushing's, acromegaly, phaeochromocytoma, thyrotoxicosis.
• Others: acanthosis nigricans, congenital lipodystrophy with insulin receptor antibodies, Wolfram syndrome (DIDMOAD),⁴ and glycogen storage diseases.

Genetic factors

These are complex⁵ and interact with environmental factors⁶ in a poorly understood fashion. Future research may clarify the situation.
The metabolic syndrome, akin to insulin resistance - Syndrome X- has recently come to notice and is thought of as a precursor to Type 2 diabetes. It is poorly defined and represents a heterogeneous collection of various propensities to diabetes. Its identification as a single syndrome and its relevance are uncertain.⁷ It has been suggested that lifestyle-intervention and treating metabolic manifestations of this pre-diabetic state can reduce the chance of progression to frank diabetes and the risk of complications.^8,9,10

Type 1 (old terms: insulin-dependent DM, IDDM)

Approximately 15% of diabetics; usually juvenile onset, but may occur at any age. It may be associated with other autoimmune disease. It is characterized by insulin deficiency.
Concordance is >30% in identical twins; 4 genes are thought to be important. One (6q) determines islet sensitivity to damage (eg from viruses or cross-reactivity from cows milk-induced antibodies). Associated with HLA DR3 and DR4 and islet cell antibodies around the time of diagnosis. Patients always need some insulin: they are prone to ketoacidosis.
Risks of developing type 1 diabetes are broadly similar in all ethnic groups, but environmental factors may also play a role.⁶The term 'Type 1a diabetes' is being applied to the development of Type 1 diabetes in adulthood. It is thought to result from a chronic auto-immune T-cell mediated islet cell destruction. Research may elucidate the underlying mechanisms, giving hope of prevention through identification and treatment of those at risk.¹¹

Type 2 (old terms: non-insulin-dependent DM, NIDDM, maturity onset DM)

Approximately 85%. Mostly an older age group and often obese. Approximately 100% concordance in identical twins. It is due to impaired insulin secretion and insulin resistance; Syndrome X. Gradual onset.
Type 2 diabetics may eventually need insulin. This does not mean that type 1 diabetes has developed.
Insulin is likely to be needed in those with:

• Ketonuria
• Glucose >25mmol/l
• Sudden onset weight loss, dehydration, ketoacidosis

Maturity onset diabetes of the young (MODY) includes several forms of diabetes with monogenetic defects of β-cell function (impaired insulin secretion); usually manifesting as mild hyperglycaemia at a young age, and usually inherited in an autosomal dominant manner.^12,13

Patients may be asymptomatic.
Acute:

• Ketoacidosis - unwell, hyperventilation, ketones on breath.
• Few weeks of weight loss, polyuria and polydipsia.

• History as above, but longer.
• In addition lethargy, infection, pruritis vulvae, boils.

Complications may be the presenting feature: infections, neuropathy and ulcers, retinopathy, arterial disease (eg MI or claudication).

The World Health Organisation (WHO) considers a patient to be diabetic if:

• They have symptoms of diabetes (unexplained weight loss, polyuria, polydypsia), plus random blood glucose (RBG) >11.1mmol/l.¹⁴
• The 2 hour plasma glucose is >11.1mmol/l, as part of a standard or abbreviated OGTT (exact diagnostic criteria are discussed in glucose tolerance tests).

Global aims of diabetic programmes are detailed in the St Vincent's declaration.

• Acute presentation: see Diabetic Emergencies.
• Subsequent management of the new diabetic: see The Newly Diagnosed Diabetic.
• Long term management: see Managing Diabetes in General Practice, Diabetes and hypoglycaemic agents and insulin regimes.
• Specific circumstances: Precautions with Diabetic Patients Undergoing Surgery, Diabetes and Intercurrent Illness and Diabetes in Pregnancy.

The aims of treatment is the avoidance of complications, which include hypoglycaemia as well as the long term consequences of hyperglycaemia.
Strict plasma glucose control does reduce renal, CNS and retinal damage, although macrovascular disease is unaffected.^15,16,17
However, a balance is required for each patient between lower blood glucose readings and the risk of hypoglycaemia.
Interestingly, tight blood pressure control is as effective in reducing microvascular disease, but also reduces macrovascular disease, and mortality.^18,19
This emphasizes the importance of a global assessment of an individual's cardiovascular risk: glucose, blood pressure, cholesterol, and smoking history. Don't treat DM in isolation.
Audit the care you provide.