Insulin is a growth hormone. Injecting insulin always in the same sites can lead to an increased formation and induration of the subcutaneous fatty tissue. Reuse of pen needles can also cause these unaesthetic dents.
Will there be further injections into this "Lipo", the resorption of insulin into the body is no longer under good control and can lead to massive blood sugar fluctuations.
Remedy: Avoiding "favorite sites": a regular rotation of the injection sites prevents the development of a lipohypertrophy.
There will be a remission of the lipohypertrophy, if there is no injection into the affected skin area for a longer time.