IGF1 is quite safe and tolerable, some may suffer from a mild hypo which is not dangerous and easy to counter with proper nutrition .

Not many consider this but IGF1 suppresses directly the natural GH production, and despite IGF1 being the GH's mediator for many of the GH's ananbolic activities the GH has some systemic effects which are not related to IGF1. And actually as you may see below GH and IGF1 have some distinctively different effects, hence it's advised to combine them, they also have some very favorable synergistic effects, here are some scientific data to support this -



http://www.ncbi.nlm.nih.gov/pubmed/9129466
------------conclusions -
GH and IGF-I combined further enhanced fat oxidation while reducing protein catabolism. Serum insulin concentrations were significantly increased by GH but decreased by IGF-I. GH significantly decreased serum total triiodothyronine concentrations and IGF-I significantly decreased serum corticosterone concentrations.
http://www.ncbi.nlm.nih.gov/pubmed/10571453
-----------results and conclusions
RESULTS:
Administration of IGF-I, but not GH, attenuates dexamethasone-induced protein catabolism and increases insulin sensitivity. Simultaneous treatment with GH and IGF-I additively increases the serum concentration of IGF-I, whole-body anabolism, and lipid oxidation. GH or IGF-I when given alone produces similar increases in the serum concentration of IGF-I. However, GH selectively increases skeletal muscle mass whereas IGF-I selectively attenuates the intestinal atrophy and abnormal intestinal ion transport induced by TPN. These tissue-selective anabolic effects of GH and IGF-I are associated with differential increases in protein synthesis in skeletal muscle and jejunum, respectively.
CONCLUSIONS:
Simultaneous treatment with GH and IGF-I may offer the greatest clinical efficacy because of improved nitrogen retention in association with enhanced lipid oxidation and stimulation of protein synthesis in multiple tissue types.