Diabetes and Lipid Clinic of Alaska

 

 


Latent autoimmune diabetes of adulthood (LADA)

The American Diabetes Association (ADA) defines latent autoimmune diabetes in adults (LADA) as the development of type 1 diabetes in adults. LADA also has characteristics of type 2 diabetes. It is known by a host of names as scientists attempt to classify this form of diabetes, which normally develops gradually in adults over the age of 30 or 35. Some of the other terms used to describe this condition include:

  • Type 1.5 diabetes
  • Autoimmune diabetes of adults (ADA)
  • Latent type 1 diabetes
  • Late–onset autoimmune diabetes of adulthood
  • Progressive insulin–dependent diabetes mellitus
  • Slowly progressive type 1 diabetes
  • Slow–onset type 1 diabetes
  • Youth–onset diabetes of maturity
  • Type one–and–a–half diabetes

While researchers continue to debate the proper name and classification for this type of diabetes, the two most common terms for this condition appear to be LADA and type 1.5. It should be noted that the term “type 1.5 diabetes” has also been used to describe two other conditions: double diabetes and maturity-onset diabetes of the young (MODY).

Compared to a child who develops symptoms of type 1 diabetes over a few weeks, the onset of LADA is more of a steady decrease in insulin production over several months or years. The additional signs of ketoacidosis (increased acid levels in the blood and urine) and rapid weight loss, normally associated with type 1 diabetes, are also absent.

Most people diagnosed with LADA are not overweight or obese and have no family history of type 2 diabetes. They may or may not have a family history of type 1 diabetes.

Treatment for LADA patients incorrectly diagnosed with type 2 diabetes will ultimately fail, and patients will become insulin dependent. Although the physician may initially believe that the patient has failed to adhere to the recommended diet or medication regimen, a physiological reaction is actually occurring inside the body.

At this point, the islets of Langerhans in the pancreas are under attack by the autoimmune process. The result is the failure of beta cells to release insulin and, thus, the production of insulin quickly grinds to a halt. For those patients with LADA, little or no insulin production takes place because the beta cells of the pancreas have been virtually destroyed by the body’s own immune system.

LADA is considered a less aggressive form of autoimmune diabetes (type 1). That may be the reason for the considerable amount of time that insulin is not required for these patients. LADA patients rarely possess some of the more common characteristics of a type 2 diabetic patient, including:

  • A high body mass index (BMI) that is in the overweight or obese category
  • A high occurrence of metabolic syndrome
  • High blood pressure
  • High triglyceride levels

Perhaps one of the most important distinctions between type 2 diabetes and LADA are the long–term health consequences. Patients with LADA usually do not have the increased risk of developing heart problems normally associated with type 2 diabetes, particularly when they are able to control their glucose (blood sugar) levels. This is significant because cardiovascular disease is considered to be the leading cause of diabetes–related deaths.

Scientists have not established the incidence of LADA. Some estimates attribute as many as 15 to 20 percent of diabetes cases to LADA, which, if correct, would make it more common than type 1 diabetes

Signs and symptoms of LADA

Latent autoimmune diabetes of adulthood (LADA) can be vexing to physicians unfamiliar with this form of diabetes – and even to those who know it well. For example, LADA patients rarely display the classic symptoms of type 1 diabetes, such as rapid weight loss or a tendency to develop ketoacidosis (a dangerous condition involving an excess waste in the blood).

With type 1 diabetes, the loss of insulin production is rapid. With LADA, the pancreas loses the ability to make insulin much slower than in type 1 but far sooner than in type 2 diabetes. LADA patients, like those with type 1, have antibodies to the insulin–making beta cells present in their blood, which means that their immune system attacks these cells.

In type 1, the cells are killed quickly, but LADA is a much slower process. Some physicians believe that this indicates that LADA is separate from type 1 and type 2 diabetes and that a different immune reaction is at work.

Also, people with type 2 diabetes are commonly overweight or obese, whereas people with LADA usually have a normal to lean build. LADA patients often do not have any of the common signs, including metabolic syndrome, high triglyceride levels, low HDL (“good”) cholesterol or high blood pressure.

Considering the high number of LADA patients erroneously believed to have type 2 diabetes, LADA should be considered if the patient who is being diagnosed:

  • Is between 35 and 50 years old. This is the typical age range, though older people have been diagnosed with LADA.
  • Has a lean build or normal to low body mass index (BMI).
  • Has not had a significant weight loss.
  • Does not present with ketoacidosis.
  • Has no known relatives with type 2 diabetes.
  • Has low c-peptide levels, an indicator of insulin levels in the blood

Diagnosis and treatment methods for LADA

The only way to determine if a person has latent autoimmune diabetes of adulthood (LADA) is through testing for pancreatic antibodies. This test is not yet part of standard clinical practice.

If LADA is suspected, a blood test is performed, where the physician is looking for the presence of islet cell antibodies (ICA), insulin autoantibodies (IAA) and/or glutamic acid decarboxylase (a beta cell protein known as GAD). The most common is the GAD protein, but any of these can confirm a LADA diagnosis.
Additionally, the level of C-peptide, a protein generated during insulin production, should be checked in a c-peptide test as this can help the physician differentiate LADA from type 2 diabetes.

For nearly half of patients with LADA, insulin supplements taken by syringe injection or other means are required within four years of diagnosis, a sharp contrast to the average of more than 10 years for patients with type 2 diabetes. In fact, it is possible for patients to go for months or even up to six years with type 2 treatments before it becomes obvious that they have LADA – and they are usually diagnosed only when they become dependent on insulin.

Thus, if LADA has been determined, most physicians recommend that insulin treatment begin immediately upon diagnosis as it may retard the autoimmune destruction of beta cells. Studies are under way to investigate ways to preserve insulin function in patients with LADA.

Although testing for LADA is not yet routine in the diagnosis of diabetes, it is expected that early identification of the condition may one day be standard. However, routine screening most likely will take place only after an effective immune intervention is developed – one that can stop the beta cell destruction and meet the unique insulin requirements of these patients.

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