As premenstrual syndrome moves into the realm of established medicine as an accepted disorder, or cluster of disorders, researchers are finding that, indeed, much of it may be "all in the head."

The difference is that the once-derogatory phrase today refers to hormones and brain chemicals--enzymes, peptides, neurons, neurotransmitters--and the way they run the body, affect behavior and feelings and are themselves affected by behavior and feelings.

Psychosomatic doesn't mean what it used to mean, even a decade ago, as specialists realize more and more how complex brain-body-mind feedbacks are.

There is, however, still a body of feminists uncomfortable with identifying premenstrual syndrome as a genuine disorder out of concern that it could then be used as another weapon to "keep women in their place."

All of these matters came into play at a recent panel discussion on PMS at the Cedar Lane Unitarian Church in Bethesda, part of a lecture series on Medicine and Society. Speakers included Dr. Katharina Dalton, the British physician who practically single-handedly gave premenstrual syndrome its medical legitimacy; Dr. David Rubinow, who is conducting PMS studies at the National Institute of Mental Health, and Estelle Ramey, Georgetown University physiologist and feminist.

Dalton--who attracted international attention by showing that the violent and criminal acts of some British women prisoners correlated directly with their menstrual cycles--uses megadoses of progesterone to treat severe PMS in her patients. She is convinced, by her own experience and a number of studies, that low levels of progesterone are responsible for most PMS cases.

As Dalton's success with PMS patients became widely known, pressures intensified here to approve her techniques and treatment. The FDA has now approved preliminary checks in this country to determine the effects of large amounts of natural progesterone (one of four female sex hormones).

Some researchers in this country, although conceding that progesterone therapy seems to work in the very serious cases, believe that the British studies are flawed. Some also are uneasy about the widespread use of such powerful steroids. (Dalton's supporters note that drugs like Valium, alcohol and other powerful sedatives and stimulants--with no evidence of effectiveness--are handed out freely for PMS.)

Based on her treatment of about 30,000 patients over the past 35 years, Dalton figures that about half of all women suffer from degrees of premenstrual problems ranging from mild moodiness or irritability to the rage and anger that result in uncontrolled violence. About 10 percent of PMS sufferers, she says, are prone to the most severe symptoms.

Rubinow, an NIMH psychiatrist, led a recent two-day conference with PMS researchers from other parts of the country to try to determine the direction of research. One of the problems, he says, is that about 150 different symptoms--from suicidal depression to hemorrhoids--have been associated with PMS. "In fact, just about any symptom one would expect to encounter in a general medical practice . . ."

Rubinow found through interviews with about 450 women who described themselves as having PMS that many may have had cyclic mood changes not necessarily--or only coincidentally--linked to the menstrual cycle. Only about 30 percent of self-referred volunteers, he says, have genuine PMS.

In the ongoing NIMH studies and experimental treatment programs, he first requires that volunteers complete daily charts measuring detailed mood changes for three full months before he feels comfortable in making a diagnosis of PMS.

One woman, he said, was so certain her problem was PMS that she traveled to London to consult Dalton and was put on progesterone therapy. After three months of evaluation at NIMH it was determined that her cycle of mood changes only occasionally coincided with the premenstrual time period.

Rubinow is still seeking subjects to evaluate and possibly treat--with progesterone, in natural and synthetic forms--and in a program with Vitamin B-6, which some studies suggest may be helpful. Interested volunteers should call 301-496-9675.

Estelle Ramey cited two recent studies relating to the self-perceptions of men and women:

* At the University of Michigan premenstrual women said they had done more poorly than males and other females on a specific examination and gave their cycle as the reason. When the exams were graded, they had done as well or better.

* A psychologist studying moods of men during a several-months-long tour of underwater duty in a nuclear submarine found to his surprise that the charted moods fell into distinct cyclic patterns, without exception.

When the men were confronted with the patterns they rejected them and, in each case, ascribed the mood change to some external situation.

For an excellent roundup of research, charts for self-diagnosis and tips for reducing symptoms: "Self-Help for Premenstrual Syndrome" by Michelle Harrison, M.D. (Matrix, $4.50). Matrix Press, P.O. Box 740, Cambridge, Mass. 02238. Add $1.50 for mail orders.)