TOKYO, Nov 13 (Reuters) - Mizuho Financial Group , Japan's third-largest lender by assets, on Monday revised its profit forecast for the full year after reporting a 2.4% drop in its second-quarter net profit.

Mizuho posted a profit of 170.56 billion yen in the July-September period versus 174.67 billion yen, according to Reuters' calculations based on six-month cumulative figures disclosed in a stock exchange filing.

For the full year through March, Mizuho revised up its profit forecast to 640 billion yen from its profit forecast at 610 billion yen, compared with the 625.56 billion yen average estimate of 14 analysts compiled by LSEG.

The main lending business stayed strong as economic activity continued to normalise from the COVID-19 pandemic, boosting funding demand from businesses and helping the bank press down credit costs.

Its U.S. business also contributed to the solid earnings as rapid rate hikes by the U.S. Federal Reserve bolstered the lender's income from loans. A weak yen inflated profits earned overseas when they were converted into yen.

The U.S investment banking business also helped drive Mizuho's profits as it won a key role in the $4.87 billion initial public offering of chip designer Arm Holdings in September.

The Japanese bank was one of the four lead underwriters for this year's biggest IPO, along with Goldman Sachs, JPMorgan Chase and Barclays.

Aiming for

a bigger share

of the world's largest investment-banking fee pool, Mizuho is completing the $550 million acquisition of U.S. boutique firm Greenhill. ($1 = 151.7400 yen) (Reporting by Makiko Yamazaki; Editing by Kim Coghill)