INSULIN INDUCED LIPOHYPERTROPHY

Lipohypertrophy and lipoatrophy of injection sites was a major problem with the old impure insulins. The problem improved somewhat with the advent of the mono-component bovine and porcine insulins and the current pure human insulins, such that lipoatrophy in particular is now very rare.

However it now manifests more subtly, with thickening of the skin  rather than the formation of lumps and pitting. Even diabetologists have been known to miss it, when not looking for it carefully. The complication has occurred with the new genetically engineered modified human insulins, with and without continuous subcutaneous insulin infusions.The question is whether there will ever be any form of insulin therapy that will be without complications.

Lipohypertrophy occurs because patients inject the same site day after day. It frequently occurs on both sides of the umbilicus or in the mid-thigh areas as these are convenient places to inject, and where the patient’s hands reach most naturally. Eventually the area becomes hyposensitive. Once the patient feels pain when injecting elsewhere, but not in the lipohypertrophic area, he or she tends to continue injecting in the same site even if aware of the need to rotate sites. 

Some classification systems neglect subtle lipohypertrophy that is not visible but only palpable, and also add lipoatrophy as the most severe form. Grouping lipohypertrophy and lipoatrophy together is inappropriate: separate mechanisms have been suggested as a cause – lipoatrophy may result from a local immune reaction against impurities of the insulin preparations, while lipohypertrophy may result from the local trophic action of insulin. Rare lipohyper- trophy syndromes associated with diabetes exist and have a poor prognosis; the term has been inappropriately used to describe the local occurrence of lipohypertrophy due to injected insulins.

DISCUSSION

Lipohypertrophy has occurred with continuous insulin delivery systems, i.e. subcutaneous indwelling catheters and insulin pump therapy. Subcutaneous indwelling catheters are placed for a period of 4 - 5 days. Patients are instructed to avoid areas of lipohypertrophy, but as has been noted above the condition is not necessarily recognised by patients and they may place catheters in areas where early lipohypertrophy is already present. In the past, lipohypertrophy and lipoatrophy caused obvious changes to the skin, and the effects were cosmetically disturbing for patients. With more subtle  presentation, there is less incentive for the patients to try to avoid lipohypertrophy. However, injecting in lipohypertrophic areas affects the rate of absorption of the insulin, contributing to erratic blood glucose control.

It has been recommended that in order to diagnose the condition sites should be palpated and not just visually examined. In order to feel subtle skin thickening the hand should be stroked firmly over the injection sites in a sweeping motion rather than using traditional techniques of light and deep palpation.

CONCLUSION
Lipohypertrophy is difficult to recognise. Extensive education is required, firstly of doctors so that they can learn to recognise the problem and be encouraged to examine closely, by palpation, for presence of the disorder. Secondly, patients need to be educated that they can avoid the problem, and to be reeducated where the problem has already occurred.

by
Akshaya Srikanth,
Pharm.D Intern
Hyderabad, India