Amgen Inc. reported fourth-quarter financial results on Thursday that beat analyst estimates on earnings. For the fourth quarter, the Thousand Oaks pharmaceutical company reported adjusted net income of $2 billion ($2.37 a share), compared to $1.7 billion ($1.68) for the same quarter a year earlier. Revenue increased 4 percent to $5.5 billion. Analysts on average expected earnings of $2.29 a share on revenue of $5.5 billion, according to Thomson Financial Network. For the full year, Amgen had adjusted net income of $8 billion ($9.06) compared to $6.7 billion ($6.70) in 2014. Revenue climbed 8 percent to $21.7 billion. Analysts on average expected earnings of $10.08 a share on revenue of $21.7 billion. The company said its total product sales were up 3 percent for the quarter compared to a year earlier, with sales from osteoporosis medication Prolia and Sensipar – which reduces calcium, phosphorus and parathyroid hormone in the blood of dialysis patients – both up 21 percent. Operating expenses decreased by 4 percent in the fourth quarter of 2015 but were flat for the year. This can partially be attributed to changes in foreign exchange rates, the company said. “2015 was an exceptional year for Amgen with six innovative new launches, strong financial performance, continued pipeline advances and improved operating margins driven by our transformation efforts,” Robert Bradway, Amgen’s chief executive, said in a statement. “We remain on track to meet or exceed our 2018 commitments and deliver value for patients and shareholders.” Amgen shares closed down $2.12, or 1.4 percent, to $148.35 on the Nasdaq.