purple is right.
And it's not like you're finding out something scandalous. If a mutual friend had said, "Oh, I ran into Old Friend; she said I should give you her number, she'd love to hear from you. She's working at XYZ Corp as a dietitian, and she has 4 kids."
So when you call, you'd say, "I hear you're a dietitian now--what's that like?" or "How are your kids--you have 4, right?"
And in fact, SHE told you this. That's part of why I put that stuff up on my Facebook page--I want the people that I "friend" to be able to know this without having to ask me directly.