COMMENTARY

Lean Adults With New Diabetes: Treatment Pearls

Anne L. Peters, MD, CDE

Disclosures

September 04, 2012

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Hi. I am Dr. Anne Peters, Director of the Clinical Diabetes Programs at the University of Southern California. Today I am going to talk about the evaluation of the adult patient with new-onset diabetes who is in the relatively lean category -- a body mass index (BMI) of less than 25 kg/m2. The reason for this discussion is a recent article published in JAMA,[1] which found that patients who are leaner at diagnosis have an increased mortality compared with those who have a BMI in the obese or overweight range. This caused concern among a number of my patients who are leaner, whose diabetes developed as adults. They called and asked, "Am I doomed?" And I said -- as I often do -- that an article does not define an individual, and, in fact, they may or may not be similar to the patients in that article. Moreover, findings from studies -- particularly epidemiologic studies -- often don't apply to an individual patient. So, although I assure them of the fact that they are getting the best possible care in terms of evaluation and treatment of complications, this sort of article makes me think in a variety of different ways. In terms of what I can teach you today, it is really about how I evaluate a lean adult patient with new-onset diabetes.

When I see a lean patient with new-onset diabetes, I look at ethnicity. Asian individuals tend to get diabetes at a lower BMI. So, I tend to evaluate those patients differently, assuming that most of them will have typical type 2 diabetes. But in a non-Asian individual -- someone who is Caucasian, African American, or even Latino -- I do a differential to determine if this is adult-onset type 1 or autoimmune diabetes, or adult-onset type 2 diabetes in a leaner individual.

To assess this, I first get a family history because if a patient has a very strong family history of type 2 diabetes and obesity, that patient is much more likely to have typical type 2 diabetes even if the patient is lean. Patients who have no family history and are not from a high-risk gene pool are somewhat confusing to me in terms of what type of diabetes they really have. For these patients I will measure an anti-glutamic acid decarboxylase (GAD) antibody.

An anti-GAD antibody is a marker for autoimmune type 1 diabetes. We know that autoimmune type 1 diabetes -- some people also call this latent autoimmune diabetes of the adult (LADA) -- can occur at any age. My oldest patient with new-onset type 1 diabetes was in her 90s. She was 92 or 93 years old and she presented with pretty florid new-onset diabetes. But I have seen adult-onset type 1 diabetes in patients of any age, from their 20s, 30s, or 40s, and the way to measure this is to look for the presence of an anti-GAD antibody. A positive antibody is suggestive of adult-onset type 1 diabetes.

Not everybody who has adult-onset type 1 diabetes will have a measureable antibody. Some won't but might appear to me to behave so much like a patient with type 1 diabetes that I will still call it adult-onset type 1 diabetes.

The reason that it is so important to differentiate between the types of diabetes is that although initially these patients may respond to oral agents because they still have some residual insulin secretion, they are going to progress much more quickly to needing insulin (usually either a multiple daily insulin regimen or an insulin pump) and they will begin to look more and more like a patient with type 1 diabetes. I tend to put these patients on basal insulin sooner, often they will need mealtime insulin to be added relatively early in the course of their disease, and I will discuss with them what it means to have adult-onset type 1 diabetes.

My final caveat is we don't actually know how much type 1 diabetes occurs as new-onset disease in adults vs in children. Recently, I was writing a chapter for a book on type 1 diabetes and realized that we don't have good data; we don't track this. In children, we track new-onset disease; we know how many have type 1 or type 2 diabetes, but not in adults. In my own practice, about one third of my patients with type 1 diabetes developed diabetes as adults. So, I have had a lot of older-onset patients with type 1 diabetes. My practice may be skewed, however, and in a general practice, there are probably fewer of these patients.

Lean patients with type 2 diabetes are people whose BMI is less than 25 kg/m2 at diagnosis. If you happen to measure a C-peptide (which is not needed to make the diagnosis), many of these patients have very high levels. They seem to be very insulin-resistant, which is surprising given the fact that they are lean. I usually associate that kind of insulin resistance with more obese patients. So, although my patients with type 2 diabetes who are lean often respond to oral medications, in my experience, they tend to need some insulin as well. They may not need mealtime insulin, but often they will need basal insulin in addition to their oral agents. I see lean patients with new-onset type 1 and type 2 diabetes, and it's important to evaluate these patients and then treat them accordingly.

Returning to the JAMA article, they looked at patients from 5 different epidemiologic cohort studies, including patients with new-onset type 2 diabetes, although some of these patients possibly actually had type 1 diabetes but weren't diagnosed with type 1 diabetes. The investigators followed these patients until they died. They found that patients who were leaner at diagnosis had an increased mortality rate compared with those who were more overweight, but the mortality wasn't from cardiovascular disease; it was from the category called "noncardiovascular death." Because these studies were designed to look at cardiovascular endpoints, the investigators didn't thoroughly evaluate noncardiovascular deaths, so we don't know why these patients died or what those risk factors would be.

In summary, I would argue that patients who are lean adults at the time that they are diagnosed with diabetes are different from those who are overweight, and in ways we don't always well-characterize. Some are going to have adult-onset type 1 diabetes; some will be lean patients with adult-onset type 2 diabetes; and in each case, we need to treat them well, evaluate for risk factors, and do our best to help prevent all sorts of issues from cancer to cardiovascular complications. Knowing what type of diabetes they have -- and their potential risks -- is important as we evaluate each patient.

This has been Dr. Anne Peters for Medscape.

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