GDNF and familial isolated pituitary adenoma: These results fit well with recent findings in a long series of human sporadic somatotrophinomas (non AIP-FIPA) that have demonstrated a six-time increase in GDNF expression over the normal pituitary, and activation of the RET/GDNF-survival pathway including AKT/mTOR activation and downregulation of p53/PARP activity [30].