Fannie Mae's gross mortgage portfolio dropped at a compound annualized rate of 16.4% in January, according to the latest monthly report from the government-sponsored enterprise.

"Fannie Mae's January mortgage investment portfolio saw the fastest decline in the seven months since the balance sheet grew to absorb delinquent loans purchased from mortgage-backed securities pools," said Jim Vogel, an analyst at FTN Financial.

The company's book of business also fell at a compound annualized rate of 1.1%. At Jan. 31, the GSE's gross mortgage portfolio balance hovered at $769.9 billion.

Meanwhile, the overall delinquency rate in Fannie's loan portfolio fell one-basis point to 0.71% in December. At the same time, the conventional single-family serious delinquency rate fell 2 basis points in December, hitting 4.48%.

Fannie Mae, which reported a fourth-quarter loss of $2.1 billion, said earlier in February it needs more federal assistance.

The government-sponsored enterprise, which was taken into conservatorship in September 2008 during the financial crisis, said its fourth-quarter loss includes $2.2 billion in dividend payments to the Treasury Department.

The Federal Housing Finance Agency requested $2.6 billion on the company’s behalf from the Treasury Department, more than 80% of which is the dividend payment.

Write to Kerri Panchuk.