Adds analyst comment in paragraph 5 and 6

May 2 (Reuters) - Cigna CI.N on Friday raised its full-year earnings forecast and beat estimates for quarterly profit, helped by strong performance in its pharmacy benefit management business and lower-than-expected medical costs in its insurance arm.

It is the latest health insurer to outperform estimates, days after UnitedHealth UNH.N missed quarterly profit estimates for the first time since 2008 and warned of high costs related to its government-backed Medicare Advantage plans, shaking investor confidence in the sector.

Cigna, however, is insulated from such cost pressures as it recently sold its Medicare business to Health Care Service Corp. It relies on its pharmacy benefit management and commercial health insurance businesses, but those too face their own challenges.

The company missed profit estimates in the previous quarter due to high costs in its stop-loss insurance plans -- which help protect health plan sponsors, typically an employer, when medical claims pass a pre-designated threshold.

Oppenheimer analyst Michael Wiederhorn said in a research note that the first-quarter results showed a strong rebound for the company.

However, he noted that its full-year forecast raise was modest relative to the magnitude of the first-quarter profit beat, and thus possibly reflects some early-year conservatism.

The company forecast an annual profit of at least $29.60 per share, above its previous estimate of $29.50 and analysts' estimate of $29.61.

In comparison, its adjusted income from operations in the first quarter rose to $6.74 per share from $6.47 a year earlier, and came in above analysts' average estimate of $6.35.

Cigna's medical care ratio - the percentage of premiums spent on medical care - rose to 82.2% in the quarter from 79.9% a year earlier - but was lower than analysts' average expectation of 82.63%, according to data compiled by LSEG.

(Reporting by Manas Mishra and Sneha S K in Bengaluru; Editing by Shinjini Ganguli)

((Sneha.SK@thomsonreuters.com;))