There are region growing based segmentation algorithms in ITK, but in “Grows from seeds” effect we use a custom grow-cut based method, which was implemented from scratch many years ago and has been continuously improved based on lots of user feedback.
The simplest is to use it from Python, either using segment editor effect API or as a plain VTK image filter (slicer.vtkImageGrowCutSegment).
If you work in C++ then you can use the filter as is (it is a VTK filter that has no other dependency than VTK) or with a little work you should be able to port it to an ITK remote module. See source code here.