(Adds insurance industry comment and background on DOJ analysis in paragraphs 7-8, 10-11) NEW YORK, Sept 8 (Reuters) - The leading U.S. physicians' organization said on Tuesday the proposed mergers of U.S. health insurers worth tens of billions of dollars would hurt competition in commercial health plans in as many as 17 states. Aetna Inc announced plans to buy smaller rival Humana Inc in early July and Anthem Inc agreed to buy Cigna Corp later that month. Both mergers are being reviewed by federal antitrust regulators as well as state insurance officials. The American Medical Association study focused on the impact of these combinations on the commercial fully insured and self insured markets, largely made up of employer-based plans. The health insurers also manage insurance plans for Medicare, Medicaid and other government programs... More