Bermuda-based reinsurer Platinum Underwriters Holdings Ltd reported a net loss of $20.4 million in the second quarter as catastrophes totalling $74.8 million took their toll on earnings.The net loss compared to a profit of $124.1 million for the same period in 2010.Platinum also posted a net loss of $177.6 million for the first six months of this year versus net income of $139.6 million a year earlier.Net premiums earned also dropped 9.9 percent or $19 million to $172.4 million, as did net investment income by four percent or $1.4 million to $34 million, while net realised losses on investments were $4.7 million versus net realised gains on investments of $49.5 million the previous year.Michael Price, Platinum’s CEO, said: “Our net income was adversely affected by natural catastrophe losses again this quarter. Our book value per common share, however, grew by 1.7 percent in the quarter to $45.43 as of June 30, 2011 aided by strong investment results on a total return basis.”He continued: “While seasonal forecasters are anticipating an elevated level of Atlantic windstorm activity this year, we enter the hurricane season strongly capitalised and well-positioned for the subsequent January 1 renewal period.”Net premiums written for the second quarter were also down 17 percent or $25.8 million at $125.9 million and the company’s GAAP combined ratio increased 52 percentage points to 119.4 percent.GAAP combined ratio rose by 76.9 points to 161.1 percent, while Platinum’s net investment income dropped nine percent or $6.5 million to $66.3 million for the first half of the year.The company’s net realised losses on investments of $4.3 million compared to net realised gains on investments of $54.9 million over the respective period.Shareholders’ equity was $1.7 billion as of June 30, 2011, a decrease of $199.7 million (or 10.5 percent) from $1.9 billion as of December 31, 2010. Book value per common share was $45.43 as of June 30, 2011 based on 37.3 million common shares outstanding, a decrease of $4.77 (or 9.5 percent) from $50.20 as of December 31, 2010 based on 37.8 million common shares outstanding.The company did not repurchase any common shares during the quarter.