Salesforce- Update lead when the user updates their user profile

We have a Wordpress site and we use Salesforce to create leads from user profiles on our site. When a user updates their profile, the default behavior is to create a new lead. We need to update the corresponding lead and associated fields if
the lead (identified by email + unique ID) already exists in Salesforce.

Ideally we should have the ability to add new fields to the profile and allow these to be synced with Salesforce also.

We have this ability already but it is not reliable and therefore would like a better solution.