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Can a person have both type 1 and type 2 diabetes at the same time?

Generally speaking, we do not diagnose both disorders in the same individual. If people have type 1 diabetes, they are completely lacking effective circulating insulin. By definition, this is not the case in people with type 2 diabetes, so having the one disorder effectively rules out the other. However, people with type 1 diabetes may be prone to the same metabolic problems as those with type 2 diabetes. In other words, if people with type 1 diabetes gain weight, become sedentary, or are members of an ethnic group at high risk for type 2 diabetes, they may become insulin resistant and their diabetes will be more difficult to control. Higher doses of insulin will be required and they may develop the metabolic problems that tend to be associated with type 2 diabetes, such as cholesterol and related blood fat abnormalities, as well as high blood pressure. These will add to their risk of cardiovascular disease. Some people with apparent type 2 diabetes appear to have a partial form of type 1 diabetes, which has stopped short of complete destruction of their insulin-producing cells in the pancreas. This is known as LADA or latent autoimmune diabetes of the adult. They tend to require insulin treatment earlier in the course of their diabetes, but are not considered to have both diseases.

Is there such a thing as borderline diabetes? What is it?

The term borderline diabetes has now been replaced by the term prediabetes. Both terms indicate that a person has abnormalities in his or her plasma glucose levels that fall short of standard accepted definitions for frank diabetes. Table 1 shows the normal ranges for both fasting plasma glucose and for plasma glucose after a glucose load by mouth. The reason that a standardized 75 gram (a little under 3 ounces) glucose load is used is to allow a direct comparison between different individuals under the same conditions. The table also shows the glucose levels above which diabetes is diagnosed. The range between the upper end of normal and diabetes itself is the prediabetic range. For lasting glucose, the range is 100 to 125 mg/dl and for glucose values 2 hours after a standard 75 gram glucose drink by mouth, it is 140 to 199 mg/dl. The former is termed impaired fasting glucose, or IFG, and the latter is termed impaired glucose tolerance, or IGT. When either is present, an individual is described as having prediabetes. There are at least two reasons why it is important to identify prediabetes. One reason is that people with prediabetes have a known increased risk of progression to frank type 2 diabetes and, second, prediabetes, especially of the IGT type, is associated with a significantly higher risk of cardiovascular disease and death. Therefore, knowledge that one has prediabetes necessitates regular follow-up and also permits early intervention to prevent progression to frank diabetes.

Table 1 Definition of Diabetes & Prediabetes

Normal Blood Sugar

mg/dl

mmol/L

Fasting

2 hours after glucose*

60-99

less than 140

3.3-5.5 less than 7.8

Preiliabetes:

Fasting

2 hours after glucose

100-125

140-199

5.6-6.9 7.8-11.1

Diabetes:

Fasting

2 hours after glucose Anytime

126 or above 200 or above 200 or above with symptoms**

7.0 or above 11.2 or above

*75 Grams of glucose by mouth.

**Such as thirst, frequent urination, weight loss or blurred vision.

Knowledge that one has prediabetes necessitates regular follow-up and also permits early intervention to prevent progression to frank diabetes. A healthy pregnant woman may be more insulin resistant than the average patient with type 2 diabetes!

Gestational diabetes mellitus (GDM)

Diabetes detected in pregnancy.

Why do some women get diabetes when they are pregnant? Is this dangerous for them or their baby?

Pregnancy is a situation in which insulin resistance (see Question 2) is a normal feature. This is because it is beneficial for the nutrients absorbed from a pregnant woman's meals to be channeled first to the growing- fetus. The development of maternal insulin resistance in the second half of pregnancy assures that this will occur. At least part of the reason for the development of maternal insulin resistance is that the placenta produces substances that lead to insulin resistance and as the placenta grows, the insulin resistance increases. This is called physiologic (i.e., normal) insulin resistance. Indeed, a healthy pregnant woman may be more insulin resistant than the average patient with type 2 diabetes! However, the vast majority (>95%) of otherwise healthy pregnant women do not get diabetes in this situation because the pancreas is able to make enough insulin to overcome the insulin resistance and keep the glucose levels normal. A small minority of women cannot do so and their glucose levels rise. These women tend to be the same women who are destined to get type 2 diabetes later in life. The risk of developing type 2 diabetes is much higher in a woman who has had diabetes detected in pregnancy (gestational diabetes mellitus or GDM). GDM provides a unique opportunity to follow the natural history of type 2 diabetes in the years prior to its onset in women, since most GDM goes away very rapidly, often within hours, after the baby is delivered and reappears in later life as tvpe 2 diabetes. If untreated, GDM can cause harm to both mother and baby, especially at or soon after delivery. Fortunately, outcomes of GDM are generally excellent in most developed countries.

 
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