"Kevan had a few off-the-field problems but he has been a very good player for us," said Iron manager Nigel Adkins.
Hurst initially struggled to adapt, but after revealing he had been affected by his mother being diagnosed with cancer he put in some fantastic performances and won fans over.
"He will have been thrilled to have helped them win promotion, and we wish him well in the Championship next season," said Blades manager Neil Warnock.
"Kevan has been desperate for first-team football for some time, and Scunthorpe have been able to do that."