* Troeim, Midelfart sold shares after sharp gains
* Storebrand's shares drop more than 6 pct (Adds analyst, background, detail)
OSLO, Feb 21 (Reuters) - Norwegian investors Tor Olav Troeim and Celina Midelfart have sold out of Storebrand, they said on Wednesday, sending shares in the insurer sharply lower.
The couple had gradually built a holding of 13 million Storebrand shares, corresponding to 2.8 percent of the company, via Midelfart Capital and Troeim's Drew Holding.
They did not give a reason for the sale, which was completed at 68.15 Norwegian crowns per share, a 2.6 percent discount to Tuesday's closing price, resulting in proceeds of 886 million Norwegian crowns ($112.85 million).
"I guess they see bigger upside elsewhere," Nordea Markets analyst Thomas Svendsen said.
By 0933 GMT, Storebrand traded 4.9 percent lower for the day at 66.56 crowns, off an earlier low of 65.12 crowns.
In September 2015, Haakon Fure was appointed board member of Storebrand to represent both Drew Holding and Midelfart Capital, the companies said, but they did not elaborate on whether he would maintain his position.
Since Fure's election, Storebrand's shares have gained more than 150 percent, partly driven by cost cuts and expectations for higher global interest rates, as well as a return to dividend payments last year after a six-year break.
Troeim and Midelfart's holdings were built up over time however, with shares bought both before and after September of 2015, making it hard to calculate their exact gain earned from the 13 million shares.
Tor Olav Troeim, Celina Midelfart and Haakon Fure were not available for immediate comment on the share sale.
Troeim, the former right-hand man of Norwegian-born billionaire John Fredriksen, is a key investor in several listed companies, including Golar LNG, and the founder of offshore drilling rig owner Borr.
Midelfart inherited her father's fortune in her early 20s and became a savvy investor. The couple who have a child have done several investments together including Storebrand.
$1 = 7.8512 Norwegian crowns Reporting by Ole Petter Skonnord, Gwladys Fouche and Terje Solsvik; Editing by Matthew Mpoke Bigg