Vice President Mike Pence’s physician abruptly resigned on Friday with no public explanation, part of a bitter feud that has led to a shake-up in the small medical office that is responsible for treating President Trump, his family and other White House officials.

The White House Medical Unit has come under scrutiny in recent days after Dr. Ronny L. Jackson, Mr. Trump’s primary physician whom he selected to be secretary of veterans affairs, withdrew from consideration amid allegations that he overprescribed medication and was drunk on the job. The president vigorously defended Dr. Jackson, a Navy rear admiral, saying he was a good man who had been falsely accused and treated unfairly.

This week, CNN reported that one source of damaging accusations against Dr. Jackson had been Jennifer Pena, Mr. Pence’s physician, who drew up memos last fall alleging misconduct by the president’s doctor, including a violation of medical privacy laws and threatening behavior.

On Friday, Mr. Pence’s office issued a short statement confirming the departure of Dr. Pena, but did not elaborate on the reason, suggesting that the matter was not handled by the vice president’s staff.