This seems to be a trend in many breeds. Our Golden Retriever, Prior Lake Jake, got up to 115 pounds at 18 months. We trimmed him back (reduced his chow) to 90-92 pounds which he easily carried.
My female rott is petite for her breed, thankfully, taking after after her mother (who tipped the scales at a solid 80lbs). Her father, who is, I kid you not, the canine Hank Hill, was MASSIVE at 145lbs-- a head the size of a cannon ball, and front paws as big as my own feet (ladies, size 9.5) Thankfully, a very even tempered, mellow dog--a true Texan.
I guess, though, if the sire is Hank Hill... the dam must be Peggy--so I guess that makes Ursa... Bobby.