Pinterest or Pintrest?

I am an avid reader, and I always have been. But, as a reader, my pronunciation sometimes leaves something to be desired. For example:

• I pronounced "paradigm" wrong for years! To this day, when I read it in a book,  I say para-dig-um in my head. A couple of years ago, I had to read something out loud to a group at work, and I had to make a conscious effort to say the word correctly. 
• I didn't realize that the T in "apostles" was silent until about a week ago. The Agent was kind enough to point this out to me. While laughing. 
• And "Pinterest." But I believe this up for debate. 

The other day, I was eating lunch with a group of girls, and one of them asked how I came up with the idea for my Halloween costume. "I can't take credit for it," I answered. "I saw the idea on Pinterest." I say Pinterest like it has three syllables: pin-ter-rest.

"Is it Pin-ter-est or Pin-trest?" a girl asked.

"Thank you!" another girl said, like she had been dying to tell me for months that I had been saying it wrong.

"I say pin-trest," a third girl  said.

I shrugged my shoulders. It's the whole potato/potato debate. And since I did not come up with Pinterest and I've never heard anyone of authority say it out loud, I really can't be sure how it's pronounced.

Except there are three syllables!

The comment that was under this picture says: "How do you pronounce 'Pinterest?' :) I've always wondered.....not sure, but I was told, 2 syllables....[I guess, like Interest, just with a P]....."

Ummm... I pronounce "interest" with three syllables, too! Am I pronouncing that wrong, too?

How do you say it? Is it Pinterest or Pintrest?