MetLife Inc, the largest U.S. life insurer, posted a first-quarter loss as its investment income dropped.

MetLife posted a quarterly net loss of $574 million, or 71 cents a share, compared with net income of $615 million, or 84 cents, the same quarter last year.

Life insurers have been hammered by weakening financial markets that have cut into their investment income. Declining equity markets have also cut into insurers' income from retirement products like annuities.

MetLife's shares have shed roughly half their value since the start of 2008.

(Reporting by Dan Wilchins, editing by Leslie Gevirtz)