Yes they go through growth spurts. when my female was growing she grew so fast the first four months it was unbelievable. Then around 6 months old, she seemed to stop for a bit. Around 8 months old she had another spurt. She is 3 years and topped out at 75lbs.
I remember that around 6 to 8 months we were convinced that Ranger was done growing - NOT! I have not weighed him since he was 8 months old (he weighed 60 lbs then) but I don't need to weigh him to know that he is much bigger than he was then. He is now 13 months and he is not huge but I would not be surprised if he weighs in at 75 or 80 lbs now.