Abc do diabetes

Abc do diabetes

(Parte 3 de 19)

Hyperinsulinaemia (normal glucose tolerance)

Diminished insulin secretion

Type 2 diabetes Natural history of Type 2 diabetes

Birthweight and Type 2 diabetes Recent observations suggest a relationship between low birthweight and the development in middle age of insulin resistance, Type 2 diabetes, and coronary artery disease. Those who are smallest at birth and largest at one year of age are most at risk.

Genetics of Type 2 diabetes Type 2 diabetes has a strong genetic component, manifest in the high concordance of diabetes in monozygotic twins, familial clustering and differences in prevalence between ethnic groups. An increasing number of specific genetic defects are becoming recognised and some are described below.

Type 2 diabetes in children and young people Hitherto, childhood diabetes was witnessed in some ethnic minorities and in those with the rare inherited MODY syndromes described below. Growing recognition now exists of a substantial increase of this disease in the prosperous industrialised nations. In the United States, between 8% and 45% of recently diagnosed cases of diabetes among children and adolescents are Type 2, and the problem is increasing. It is most likely to occur at 12 to 14 years of age, more frequently in girls, and is strongly associated with obesity, physical inactivity and a family history of Type 2 diabetes. When young people of lean physique are discovered to have Type 2 diabetes, it is important to attempt to identify whether they may represent those with LADA and thus in need of insulin. There is also evidence that in approximately one-quarter of such patients diabetes is due to a specific genetic defect including those of the MODY group described below or other rare genetic syndromes.

Dominantly inherited Type 2 diabetes (MODY) Seven genetic syndromes, three of which are shown in the box at the top of page 2, cause MODY—defined as an early onset of dominantly inherited Type 2 diabetes. Two (or at the very least one) members of such families should have been diagnosed before 25 years of age, three generations (usually first-degree) should have diabetes, and they should not normally require insulin until they have had diabetes for more than five years.

Mitochondrial diabetes Mitochondrial diabetes and deafness is a rare form of diabetes maternally transmitted, and is related to the A3243G mitochondrial DNA mutation. Diabetes is diagnosed in the fourth to fifth decades, usually in thin patients with symptoms. Patients respond better to sulphonylureas than to diet alone. Diabetic microvascular complications do occur.

Insulin resistant diabetes Some rare insulin resistant states exist in which hundreds or even thousands of units of insulin may be ineffective. They are often associated with lipodystrophy, hyperlipidaemia, and acanthosis nigricans. Type A insulin resistance is due to genetic defects in the insulin receptor or in the post-receptor pathway. Type B insulin resistance occurs as a result of IgG autoantibodies directed against the insulin receptor; it is often associated with other autoimmune disorders such as systemic lupus erythematosis, and it is much commoner in women of African descent. Management of these conditions can be very difficult and specialist texts should be consulted.

ABC of Diabetes

Body mass index (kg/m)

Age-adjusted relative risk of Type 2 diabetes

Relative risk of Type 2 diabetes according to body mass index in US women aged 30 to 5 years

A family with dominantly inherited Type 2 diabetes. HNF-1 defect (chromosome 12), formerly MODY 3. Diabetic patients are shown in black

Prevalence

In the United Kingdom more than three percent of the population have diabetes, and about the same number again can be found on screening in population studies. Among schoolchildren about two in 1000 have diabetes.

Diabetes can occur at any age. Type 2 diabetes is most common after middle age and occurs most often at 50-70 years of age, affecting both sexes equally. The peak incidence of Type 1 diabetes is at 10-12 years with a small male predominance. Nevertheless, elderly people can also have Type 1 diabetes, and some children have Type 2 diabetes.

Worldwide, the incidence of Type 2 diabetes is increasing rapidly: in 1995, it was estimated that there were 135 million people with diabetes, this may rise to about 300 million by 2025, increasing particularly in developing countries.

Ethnic variations The prevalence of Type 2 diabetes is particularly high in Asian and African-Caribbean people and presents a considerable health burden in some inner urban areas. Thus in the United Kingdom 20% of Asians and 17% of African-Caribbeans over 40 years of age have Type 2 diabetes. Children not infrequently have Type 2 diabetes. Asian people have a particularly high risk of developing diabetic nephropathy and coronary artery disease, and a very low risk of foot ulceration; those among the

What is diabetes?

Age at onset (years)

Number of patients

200 Boys

50 Girls

Age of onset of Type 1 diabetes in 3537 children from the British Diabetic Association (now Diabetes UK) register

Hong Kong

Pakistan

Czech Republic

Singapore

Egypt Cuba

New Zealand USA Japan Israel

Hungary Malaysia

Korea Greece India Poland Finland Portugal Indonesia

Turkey

Venezuela Colombia

South Africa

Norway Thailand

Peru

United Kingdom

Argentina

Brazil Ireland

Philippines China (PRC) Chile

Estimated prevalence of diabetes mellitus in selected countries in 2000 Developed Developing World

Millions

Number of people aged 20 years estimated to have Type 2 diabetes in developed and developing countries

Month

Number of cases

O N D J F M A M J J J F MAMA S O N D 0

100 Total

Seasonal incidence of the onset of Type 1 diabetes showing that nearly three times as many of the older children develop the disorder in the winter months, suggesting some role for viral infections black races are prone to severe hypertension that can be difficult to treat, and also have a strong tendency to develop gestational diabetes.

(Parte 3 de 19)

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