The widow of Sen. John East (R-N.C.) has filed suit in U.S. District Court blaming the former attending physician of the Capitol and two doctors at Bethesda Naval Medical Center for failing to diagnose a thyroid ailment that she says led her husband to become deeply depressed and commit suicide.

Priscilla East is suing the federal government for $10 million for the wrongful death of her husband, who was found dead June 29, 1986, on the floor of his carbon-monoxide-filled garage in Greenville, N.C.

In her suit, filed Monday in Baltimore, East alleges that her husband underwent repeated exams over a two-year period with Adm. Freeman Cary, then at the Capitol, and Navy doctors, Capt. Ralph Gemelli and Capt. Kevin O'Connell, and his condition was not diagnosed as a thyroid ailment until after he slipped into a coma.

By the time that East was found to have hypothyroidism, a disease whose most common symptom is fatigue and depression, his ailment was so advanced that he did not respond well to thyroid replacement therapy, the suit says.

A year after the diagnosis, East, 55, was still suffering from listlessness and depression, the suit says, and "his ability to make decisions was so impaired that frequently he would try on six suits in the morning in an attempt to decide what to wear . . . .

"He could no longer read and understand the voluminous material necessary to cast a well-informed vote on the Senate floor. His thinking was clouded and he was constantly distracted. He acted as if he were constantly in a daze.

"As many as 15 times a day, he would telephone home and speak to Mrs. East or his daughters, crying and telling them he could not go on."

Such depression led East, a polio victim who had used a wheelchair since law school, to abandon reelection plans and to kill himself, the suit alleges.

Navy spokemen said yesterday they could not respond to the suit but said East's effort follows the rejection of an administrative claim she filed in February 1987 under the Federal Tort Claims Act. That claim for damages was reviewed and denied in May.

"It is certainly within their right to go one step further," said Lt. Janet Mescus, Navy spokeswoman who would not elaborate on the suit.

The Washington Post reported shortly after East's death that the senator left a suicide note that blamed Cary and Bethesda Naval Hospital. According to five people who saw the note, which was not made public by the family, East wrote: "Dr. Cary and Bethesda Hospital failed to diagnose my hypothyroidism (as they should have). They ruined my health." The parenthetical phrase was East's.

Priscilla East and the three doctors could not be reached for comment last night. Cary, a cardiologist, joined the Office of the Attending Physician in 1972 and became head of the office in 1973. He went on leave in July 1986 at a time when questions about East's care had been raised and retired from the Navy in September when he turned 60.

East committed suicide after what friends and associates described last year as a series of mysterious health problems. According to interviews with aides and friends in Washington, East began suffering occasional days of fatigue in 1983 and eventually had to cut back sharply on his schedule. By 1985, East's disorientation was becoming increasingly noticeable. He was so fatigued he spent nights in his office because he didn't have the strength to go home, they said.

East continued to receive treatment from Cary and the other Navy doctors during that time, according to the suit filed this week. It was not until April 1985, after East collapsed at home and was admitted to a psychiatric ward at Bethesda Naval Hospital suffering delusions, that doctors completed blood tests that led to the discovery of the thyroid ailment, the suit said.