Defense Secretary Lloyd Austin’s mysterious hospitalization is related to a prostate cancer diagnosis he received in December, Pentagon officials revealed Tuesday.

Austin has been hospitalized at Walter Reed National Military Medical Center in Bethesda, Maryland, since New Year’s Day for a complication related to a Dec. 22 operation on his prostate gland.

But news of his condition was not immediately shared with senior Biden administration leaders or even top Pentagon officials, prompting heated questions about the lack of information at a time when the U.S. is involved in several global conflicts.

“His prostate cancer was detected early, and his prognosis is excellent,” said a letter from Austin’s doctors released Tuesday.

Austin, 70, received a general anesthetic last month during his prostatectomy, a procedure that involves the full or partial removal of the prostate, and returned home the following morning.

His doctors said that he returned to Walter Reed on Jan. 1 with nausea and severe pain that turned out to be symptoms of a urinary tract infection. Austin was placed in an intensive care unit while doctors addressed the “back up of his intestinal contents” by “placing a tube through his nose to drain his stomach,” the letter said.

The doctors reported that the top commander’s infection “has cleared” and he never lost consciousness during the treatment, which was administered with another general anesthetic.

Austin had put Deputy Defense Secretary Kathleen Hicks in charge in his absence, although she was working remotely from Puerto Rico. The Pentagon announced Monday that Austin had resumed his duties Friday evening.

In a statement last week, Austin took full responsibility for the delays in notification. The White House had said it was kept in the dark about Austin’s hospitalization for three days.

Biden found out about Austin’s cancer diagnosis Tuesday morning when he was informed by White House chief of staff Jeff Zeints, according to White House National Security Council spokesperson John Kirby.

This week, the Biden administration ordered Cabinet members to notify the White House if they ever cannot perform their duties.

Maj. Gen. Patrick Ryder, the Pentagon’s press secretary, would not provide information about the timeline or Austin’s reasons for keeping his condition secret. A review of the events is underway.

“Prostate cancer and the associated procedures are obviously deeply personal,” Ryder told reporters, pledging better transparency “moving forward.”

He added: “I think we really need to allow this review to run its course.”

Told that it seemed like Ryder himself was “deceived,” the spokesperson declined to offer further comment.

President Joe Biden has said he has no plans to replace his defense secretary.