Actors Jim Carrey and Jenny McCarthy ended their five-year relationship by announcing the split on their Twitter pages on Tuesday.

The announcement surprised Hollywood insiders as the low-profile couple appeared to have a durable union, and Carrey passionately advocated a link between vaccines and autism, a neurological disease suffered by McCarthy's 7-year-old son.

On Valentine's Day, Carrey, 48, hired a plane to sky-write J (heart) J above the home they shared in the upscale Los Angeles neighborhood of Brentwood.

Jenny my Love, you've stolen my heart, my soul and of course anything you find in my pants, he cooed in a follow-up Twitter message.

But both were singing a different tune on Tuesday.

Jenny and I have just ended our (five-year) relationship, Carrey wrote. I'm grateful (for) the many blessings we've shared and I wish her the very best!

McCarthy, 37, was equally amicable, writing that she was grateful for their time together, and would always keep Jim as a leading man in my heart.

In the early days of their relationship, Carrey wooed McCarthy by taking her on a helicopter ride and to concerts by Radiohead and Fiona Apple, according to a People magazine report in 2006.

In recent years, Carrey and McCarthy entered the emotional debate about the causes of autism, strenuously defending medical researchers who believed the disease was caused by vaccines. McCarthy's son Evan was diagnosed with the disease in 2005, a disclosure that strained her first marriage to actor/director John Asher.

Carrey, who has a daughter from the first of his two marriages, recently became a grandfather for the first time. His most recent on-screen appearance was in the 2008 comedy Yes Man, which earned $223 million worldwide. McCarthy, a former Playboy Playmate, is writing a book about relationships.

(Reporting by Dean Goodman; editing by Mohammad Zargham)