The reason Teresa Heinz Kerry has been hospitalized is not known at this time:

From the Boston Globe:

Noah Brown, public information officer for Nantucket Cottage Hospital, said Heinz Kerry arrived at the hospital this afternoon but could not disclose the nature of her illness.

“She was brought in, in critical but stable condition, and that is currently how … her condition still remains,” Brown said shortly after 5:30 p.m. “At this point, we are determining the next phase of her care, be that either in our facility on the island, or on the mainland.”

On Twitter, many are sending well-wishes:

https://twitter.com/James_in_TX/status/354005226317025280

https://twitter.com/akuakyerematen/status/354003935343820800

Twitchy joins these people in wishing her a speedy recovery.

Update:

Update: Actor Rob Lowe sends prayers and good thoughts:

(h/t @einfal)