American Express Co., the biggest credit- card issuer by purchases, said fourth-quarter profit fell 38% as expenses rose and the company took a restructuring charge.

Net income slid to $899 million, or 89 cents a share, from $1.45 billion, or $1.39, a year earlier, the New York-based company said Thursday in a statement. Adjusted earnings, which excludes a $335 million restructuring charge, beat the $1.12 average estimate of 30 analysts surveyed by Bloomberg.

Chief Executive Officer Ken Chenault, 64, is overhauling AmEx’s management and revamping its consumer businesses as the lender grapples with the loss of its biggest partner, Costco Wholesale Corp., and tries to end its steepest stock slump since the financial crisis. Quarterly results will be uneven and expenses are expected to rise as the company spends money to attract new customers, Amex has said.

Revenue fell 7.6% to $8.39 billion, matching the average estimate of 20 analysts surveyed by Bloomberg. Expenses rose 1.5% to $6.37 billion.

Amex shares fell 25% in 2015, the third-worst performance in the Dow Jones Industrial Average. The stock has slid 9.9% this year to $62.64. Visa Inc., the world’s largest payments network, rose 18% last year and MasterCard Inc. increased 13 percent.

Last year, American Express said it was ending its U.S. partnership with Costco, a relationship that accounted for 20% of Amex’s worldwide loans and 8% of customer spending. Citigroup Inc. will replace Amex as the issuer for Costco’s co-brand cards in March, a deal that’s subject to Citigroup’s purchase of the existing loan portfolio. AmEx said this month it hopes to sign an agreement with Citigroup by the end of February and complete the sale by mid-year.

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