Sen. John P. East (R-N.C.) committed suicide last month after suffering for several years from a debilitating thyroid disease that went undiagnosed by his physicians until April 1985, when he went into a rare, near-fatal coma caused by the illness.

In a handwritten suicide note found next to his body, East blamed his doctor, Rear Adm. Freeman H. Cary, the attending physician of the U.S. Capitol, and the Bethesda Naval Hospital for failing to detect the disease, which he told friends had severely diminished his intellectual abilities.

According to five people who saw the note, which has not been made public, 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.

Cary, during the past two weeks, declined in two interviews to discuss East's treatment, citing the confidentiality of doctor-patient relationships. When told the contents of the suicide note Tuesday, Cary said only: "He East obviously wasn't in a good state of mind when he wrote that note."

A Navy spokesman said Cary will be released from active duty in September and that he went on leave yesterday. The spokesman described the release as routine, pointing out that as a reserve officer Cary is required to retire when he turns 60, which he will in September. Cary asked to take accumulated leave time up to his release. The spokesman said all questions concerning Cary would have to be answered by Congress, which operates the Office of the Attending Physician.

The spokesman also said that the East case is under review by the Navy.

East, a polio victim who had used a wheelchair since before going to law school, was found dead June 29 on the floor of his carbon-monoxide-filled garage in Greenville, N.C. He left the note on top of a garbage can next to his family's station wagon.

The suicide ended three years of mysterious health problems, which began with occasional days of fatigue and became weeks of exhaustion that led East to cut back his schedule and spend nights on a bed in his office because he did not have the energy to go home.

Finally, it included a frightening weekend of disorientation and delirium that sent East to Bethesda Naval Hospital, where he was first diagnosed as a psychiatric patient before he went into the coma.

After the hypothyroidism was diagnosed, East was treated for the condition by drugs. But aides and friends said he was obsessed by Cary's failure to diagnose the disease, despite annual physical examinations and periodic office visits to complain about tiredness and fatigue. East family members declined to discuss his illness.

"He always returned to the same theme," said Sen. Alan K. Simpson (R-Wyo.). "He'd say, 'I don't understand how this disease could have gone on this long without being diagnosed by this community of fine medical personnel.' It was very vexing to him."

Dan Caprio, one of eight former East aides interviewed, said, "He felt he lost his mental abilities . . . . For someone like the senator who was paralyzed from the legs down, his mental capability was very important . . . . It's hard for us to realize the magnitude of his feelings ."

East's symptoms, which apparently began in mid-1983 and grew increasingly noticeable over the next 18 months, were typical of hypothyroidism, a disease that occurs when the thyroid gland is unable to produce two hormones necessary to keep the body's metabolism at a normal level. The most common symptom is fatigue, which makes the disease difficult to diagnose at an early stage, several medical experts said in interviews.

As the disease progresses, the symptoms become more characteristic of hypothyroidism: depression, muscle weakness, dry skin and lapses in concentration. A coma is "extremely" rare and should not occur, said Dr. Gilbert Daniels, co-director of the thyroid clinic at Massachusetts General Hospital and associate professor of medicine at Harvard University.

The persistence of the symptoms ordinarily leads a doctor to request a simple blood test to check for hypothyroidism, said Dr. John J. Canary, who examined East in late 1985 after East's thyroid condition became known. Canary, a professor of medicine at Georgetown University Hospital, would not discuss East's case specifically.

After the onset of the disease, medication usually relieves all symptoms within three months, the experts said. In some extreme cases, Canary said, there are long-term psychological problems, including depression. "Some people feel their intellectual ability has changed," he said.

In retrospect, his aides and friends said, the change in East was obvious. He arrived in Washington in 1981 with a reputation as someone who might become a key member of the New Right. He was an active man who relished debates, swam regularly to exercise his polio-stricken legs and drove a station wagon equipped with hand controls.

His typical day was a whirl of activity: speaking and voting on the Senate floor, even for the most routine of roll calls; attending luncheons with constituents; granting interviews to reporters, and regularly attending at least two subcommittee or committee hearings.

Three years later, said former spokesman Jerry Woodruff, East was too tired to keep up his exercise regimen. In 1984, he cut back on public appearances, stopped giving news conferences in North Carolina and declined two subcommittee chairmanships, telling his staff, "I can only bite off so much."

He went to the Senate with considerable energy. As chairman of the Judiciary Committee's subcommittee on separation of powers, East held 26 days of hearings on 10 subjects between January 1981 and June 1983. In the next 18 months, he presided over only one hearing -- in November 1983. It lasted two hours.

East did not complain to the staff about his fatigue until after his coma, but he could not hide the symptoms. Looking back, Woodruff remembers the fatigue beginning in late 1983. East started to take afternoon naps, asked Woodruff to curtail his schedule and stopped exercising on his crutches, which he used to improve his circulation.

The aides could not determine how many times East saw Dr. Cary in this period, but they remember him making appointments on the spur of the moment. The Office of the Attending Physician is located in the Capitol and a number of lawmakers use it. Cary, a cardiologist, has run the office since 1973.

Later, after his coma, East told the aides that he had talked to Cary about the fatigue during these visits.

In the spring of 1984, East stunned his staff when he begged off a subcommittee hearing and asked Sen. Jeremiah Denton (R-Ala.) to sit in his place, although the subcommittee was holding a hearing on a Denton bill.

"None of us understood it," said a former senior aide who asked not to be identified. "Until his hypothyroidism was diagnosed, he East never said the 'the reason I'm not doing this is that I don't have the energy.' He just said, "I'm not doing this.' And I couldn't understand why."

In February 1985, East went to Bethesda Naval Hospital for surgery on the urinary tract and underwent a routine blood test. But such a test would not indicate hypothyroidism unless the laboratory workers specifically checked for it.

In mid-April, Woodruff said, there was one incident in particular that stood out in hindsight. Woodruff told East that the North Carolina Broadcasters' Association wanted him to appear on a public service commerical against drunken driving.

The filming was set for April 18, Woodruff said. Just before the film crew arrived, East appeared to have forgotten that he had agreed to the filming. "Have we already agreed to this? " Woodruff remembers East asking. Woodruff said he reminded East of their conversation. "Could we do it later?" East asked. Woodruff said no.

In years past, Woodruff said, East spoke on camera without notes, ad-libbing easily. But on this day, he had trouble remembering the three-sentence script. With the cameras running, East glanced at the script, said a few words, then stumbled and glanced at the script again. He stumbled twice more.

Woodruff remembers thinking it strange. "I thought something was on his mind, something was bothering him."

The following day, a Friday, East went home to his Alexandria condominium and had trouble sleeping for the third night in a row, according to a friend, Palmer Stacy. The next day, East became disoriented and his wife, Priscilla, and a friend took him to Bethesda Naval Hospital, Stacy said.

At the hospital, the senator was admitted and treated as a psychiatric patient. An aide said later that East was delirious while he was the hospital. One doctor knowledgeable about the case said East went into the coma -- called a myxedema coma -- after receiving medication.

Dr. Canary said that medication can induce a coma because hypothyroid patients cannot metabolize drugs at the same rate as other patients.

One of East's medical records, according to one source, said that doctors at Bethesda linked the coma to untreated hypothyroidism. It is unclear how long it took for doctors at Bethesda to revive him from the coma.

After East was revived, he was given medication to synthetically replace the hormones of the thyroid gland. He was released from Bethesda after five weeks.

Blood tests showed that his TSH level -- a measurement that determines the severity of his illness -- was 100, evidence of a severe case. Normal levels are 6 to 10, medical experts said.

"You have to have a severe case to go into a coma," Daniels, the Harvard professor, said. Medication can trigger a coma, Daniels said, but not unless the illness has already progressed to a severe point.

After East left Bethesda, he told friends and aides that he had repeatedly complained to Cary about this fatigue. Sen. Simpson said they talked about the case, although Simpson did not elaborate about their conversations. Simpson did say: "He East said they the naval physicians were appalled when he got to Bethesda that he had reached that condition."

About six weeks after he left Bethesda, East returned to the Senate, still taking the synthetic thyroid pills and an antidepressant, according to two doctors. East underwent periodic blood tests, according to his aides.

"East was totally withdrawn, couldn't have conversations, he was very quiet," said a former senior aide who asked not to be identified. "He had a fearful look in his eyes. His voice was high-pitched and nervous and fast and it didn't sound like him. He never said anything on the Senate floor. He wouldn't say one word in public. He would vote but that was it."

In the fall of 1985, East regained some vigor. He had long conversations with a former senior aide, telling him he couldn't understand why Cary hadn't diagnosed his hypothyroidism earlier.

About the same time, East went to Georgetown University Hospital for a "second opinion" on his hypothyroidism, according to Dr. Dudley Jackson, one of East's physicians at Georgetown.

Physicians there found through blood tests that East had a dangerously low white blood count of 500, according East's medical record at the hospital. The lower limit of normal at the Georgetown laboratory is about 4000.

According to East's medical record at Georgetown, the low white blood cell count was caused by the antidepressant drug East had been taking since his hospitalization at Bethesda Naval Hospital.

"The doctors were very worried about it because his body wasn't able to fight infections," Woodruff said.

Jackson said East was taken off the antidepressant drug and his white blood cell count was restored to normal range before his release from Georgetown on Dec. 6, 1985.

East repeatedly told aides that he believed he was less mentally sharp as a result of the disease. He appeared depressed and his self-confidence was eroded, the aides said.

"Before East's coma he'd speak up, be very aggressive and self-confident" on the Judiciary Committee, said a former senior aide. "This is someone who rose above polio to get a Ph.D., a law degree and became a U.S. senator. But in the fall of 1985 when he did participate a bit, he was very nervous and felt he had done terribly. He couldn't be objective and see that he had done fine."

Said former aide Dan Caprio: "He just felt his thyroid condition had robbed him of his mental capability. There is nothing you could do or say that would convince him otherwise.