Difference between OS X md5 and gnu md5sum [closed]

Difference between OS X md5 and gnu md5sum [closed]

I have installed the "md5sum" utility on my Mac and there was also a "md5" binary pre-installed in /sbin.
My problem and question is this: "Isn't MD5 a standard algorithm?"
Because I get different hashes for a string using these utilities
Are there any differences in these utilities' implementations? Example:

Mehdi-MacBook-Pro:~ mehdi$ md5 -s Hello
MD5 ("Hello") = 8b1a9953c4611296a827abf8c47804d7

Mehdi-MacBook-Pro:~ mehdi$ echo Hello | md5sum
09f7e02f1290be211da707a266f153b3  -