NEW YORK (Reuters) - Booming stock markets around the globe helped Goldman Sachs Group Inc GS.N offset declines in other businesses last quarter, but those gains may not be sustainable, analysts said.

The Goldman Sachs company logo is seen in the company's space on the floor of the New York Stock Exchange, (NYSE) in New York, U.S., April 17, 2018. REUTERS/Brendan McDermid

The biggest contributor to the bank’s profits was the $1.5 billion it notched from its own equity investments – including $375 million from electronic trading company Tradeweb – some of which it sold during the second quarter.

Its investment bankers also handled more stock offerings than any rivals during the period, which in turn helped boost revenue from equity trading, where Goldman is also nabbing market share.

These were all bright signs in otherwise dreary results for Goldman Sachs, however. Its revenue from other major businesses, including bond trading, M&A and investment management, all fell.

Analysts warned that without more insight into how Goldman racked up equities gains last quarter and the stock market facing headwinds, they are not giving the results much weight.

“We consider these to be solid results given the operating environment ... but they underscore the importance of the firm’s strategic initiatives,” wrote David Fanger, senior vice president at Moody’s.

Excluding the gains from Tradeweb, Fanger said the bank is facing “muted client activity levels...investor concerns over trade and tariffs, uncertainty over shifts in central bank policy, and tighter credit markets compared with a year ago.”

Goldman Sachs is in the middle of a front-to-back business review launched by new Chief Executive David Solomon aimed at adding new businesses like credit cards and cash management to diversify the bank’s revenue streams. Goldman’s IPO investments were the biggest star of the second quarter. The investing & lending division reported net revenues of $2.5 billion, its highest in 8 years.

The bulk of revenues came from the performance and some sale of investments in Tradeweb Markets Inc, Avantor Inc AVTR.N, Uber Technologies Inc UBER.N and Headhunter Group Plc HHR.O, which together make up 55 percent of the bank's public investment portfolio.

While competitor banks JPMorgan Chase & Co JPM.N and Citigroup C.N also reported big gains this week from investments in Tradeweb, Goldman's gain had a proportionately bigger impact because it is smaller, analysts said.

Still an adroit trading house, Goldman reported equities trading revenues of $2 billion, or a 6 percent rise from last year, outperforming rival banks that reported equities revenue declined.

The bank said it benefited from improved client activity and market share.

Deutsche Bank AG DB.N put its share of the market up for grabs earlier this month when it said it would close its equities trading business.

“The success that Goldman had this quarter (in equities trading) is definitely a more sustainable performance than the large gains in the investing & lending business,” said UBS analyst Brennan Hawken.

“To the extent that people want to trade they’ll continue to have momentum there with clients.”

(This story was refiled to add “face” to headline.)