UPDATE 1-Pinterest forecasts quarterly revenue above estimates, shares surge

(Adds shares in paragraph 1)

April 30 (Reuters) - Pinterest forecast second-quarter revenue above Wall Street estimates on Tuesday, expecting a boost from growing advertising spend on the image-sharing platform, sending shares up more than 20% in after-market trading.

The company has benefited from marketers turning to the digital platform to reach Gen Z users - more than 40% of its user base - and leverage its new AI-driven ad tools and latest ad formats, which offer better user engagement.

Last month, ad group Interpublic Group's media research unit MAGNA Global said it expects the U.S. ad Market to grow by more than 9% this year to reach $369 billion.

The company expects second-quarter revenue to be between $835 million and $850 million, compared with analysts' average estimate of $826.5 million, according to LSEG data.

In the first quarter, global monthly active users (MAUs) rose 12% to 518 million, compared with estimates of about 503.2 million users.

Revenue for the first quarter ended March 31 rose 23% from a year earlier to $740 million, beating estimates of $699.9 million.

A majority of Pinterest's first quarter ad spend in the U.S. came from the shopping category at 50%, followed by 20% from consumer packaged goods (CPG), while 6.4% came from the health and wellness category, market intelligence firm Sensor Tower told Reuters on Monday.

The top five U.S. advertisers on Pinterest were Amazon.com , Target, PDD Holdings-owned Temu, Walmart and French cosmetics giant L'Oreal, making up 29% of the total ad spend in the quarter, Sensor Tower added.

(Reporting by Jaspreet Singh in Bengaluru; Editing by Tasim Zahid)