What 4iu/ed means.

I've seen often in powerfull cycles 4iu/ed of hsg, and on less powerfull cycles 500iu/wk.



I don't get it.



I know what ed/wk/hsg means, I just don't get it why such low hsg on powerfull cycles and more on less powerfull cycles.

What 4iu/ed means.