Amgen (AMGN) reported late Thursday a better-than-expected fourth-quarter profit on strong demand for its top osteoporosis drugs that helped offset a decline for anemia treatment Aranesp.   

The world’s largest biotech company posted net income of $934 million, or $1.09 a share, compared with $1.02 billion, or $1.08 a share, in the year-earlier period.

Excluding one-time items, the company earned $1.21 a share, just behind average analyst estimates of $1.22 in a Thomson Reuters poll.

For the full year, the company earned $5.33 a share, matching the Street’s view. Amgen raised its profit forecast to a range of $5.15 to $5.30 in October shortly after announcing a 6% workforce cut in research and development to free up cash for pricey late-stage trials.

Amgen, which closed down about 1.6% before the closing bell, rebounded nearly 1% after hours.

Revenue for the three-month period climbed 3% to $3.97 billion from $3.84 billion a year ago, edging just ahead of average estimates of $3.91 billion.

The Thousand Oaks, Calif.-based maker of biologic drugs that help fight cancer and blood disorders attributed the 4% increase in product sales to growth of 31% and 59%, respectively, of osteoporosis drugs Xgeva and Prolia.

“We exited 2011 with good momentum and the outlook for 2012 is even stronger,” said Kevin Sharer, chairman & CEO of Amgen. “Our acquisition of Micromet, announced today, further builds our innovative oncology therapeutics pipeline and capabilities.”

Quarterly gains were partially offset by a 15% drop, to $538 million, of anemia treatment Aranesp, due to weakened demand and changes to the product label.

Amgen chief operating officer Robert Bradway told analysts earlier this month that revenue growth would accelerate in 2012. The company forecast 2012 revenue between $16.1 billion and $16.5 billion, Wall Street is looking for a profit of $16.05 billion.

It projects full-year earnings between $5.90 and $6.15 a share, in line with Wall Street’s $5.94 forecast.

Bradway will become Amgen’s fourth-ever CEO when Sharer steps down in May.

Follow Jennifer Booton on Twitter at @Jbooton