Diabetes mellitus is a disease of disturbed carbohydrate metabolism, characterised by hyperglycaemia. An absolute or relative decrease of insulin secretion caused by the malfunctioning of the beta cells of the pancreas, and insulin resistance in liver, muscular and fatty cell tissue contribute to the development of type 2 diabetes mellitus (T2DM). These metabolic abnormalities may also contribute to the development of other clinical conditions, such as hypertension, dyslipidaemia and obesity. The pathogenesis is multifactorial, with genetic factors (impaired insulin secretion) and environmental factors (insulin resistance: overeating, sedentary lifestyle). Altogether, T2DM may lead to severe microvascular (neuropathy, retinopathy, nephropathy) and macrovascular (coronary heart disease, stroke) disease. This implies that patients with T2DM must be encouraged to adopt a healthy lifestyle aimed at not only reducing hyperglycaemia but also at the reduction of all risk factors for microand macrovascular disease. Moreover, the monitoring of, and, if necessary, treatment of their metabolic abnormalities is indicated.
Symptoms of diabetic hyperglycaemia may be thirst, polyuria and weight loss, although most patients do not experience these symptoms at the time T2DM is diagnosed. Hyperglycaemia is often noted during routine laboratory testing and a diagnosis is made with two fasting plasma glucose values ≥7.0 mmol/l taken on two different days. The diagnosis can also be made with one fasting plasma glucose value ≥7.0 mmol/l or one non-fasting plasma glucose value ≥11.1 mmol/l in combination with hyperglycaemic symptoms. Because not all patients with T2DM will develop symptoms or vascular complications, T2DM might be considered a risk factor instead of a disease in asymptomatic patients.
Pharmacologic treatment is needed in most cases to attain treatment goals, namely, the prevention and treatment of symptoms and complications, for example: (the progression of) cardiovascular disease, chronic renal insufficiency, retinopathy and neuropathy. Options have expanded to various medication categories, such as metformin, sulfonylureas (SU derivatives) and insulin, along with newer medication types such as SGLT2 inhibitors and GLP-1 receptor agonists. Our knowledge of diabetes and its treatment is constantly being developed with updates of treatment recommendations every few years. Treatment recommendations are increasingly personalised, with pharmacological options based on the patient’s risk of complications and comorbidity. As a result, diabetes management has become increasingly complex. Yet, in the Netherlands, it is mainly managed in primary care.
In Type 1 diabetes mellitus, the autoimmune destruction of beta cells causes absolute insulin deficiency. Type 1 diabetes generally presents with symptomatic hyperglycaemia in children or adolescents and, in 25%, as diabetic ketoacidosis. (Subtypes of) Type 1 diabetes may be diagnosed in adults. Type 1 diabetes is managed in secondary care.