It is the opinion of Wustenberger-Land German Shepherds that a German Shepherd puppy male or female needs its hormones to become a healthy adult. We recommend allowing them to mature at least to the 24 month mark. A German bloodline shepherd takes at least two years to mature.
I am attaching a link to a case study done on the pros/cons of spay/neuter. This should help you decided what is best for you and your new German Shepherd.
http://www.naiaonline.org/pdfs/LongTermHealthEffectsOfSpayNeuterInDogs.pdf