Héloïse's uncle, Fulbert, sent men to castrate Abelard because he was outraged that Abelard had taken Héloïse as his mistress. Fulbert had arranged for Abelard to marry Héloïse, but Abelard refused. Fulbert then had Abelard castrated in order to prevent him from having any more children with Héloïse.
The Enlightened Minds of Peter Abelard: Unravel the Legacy of a Remarkable French Scholar