PITY THE POOR medical student.

Annual tuition is going up and up and now exceeds $15,000 at several American medical schools. By the time they graduate, most medical students are deeply in debt; those who are report an average indebtedness of about $20,000. By the time they finish their residencies and enter practice, that figure will grow. And, if they choose surgical practice, they face malpractice insurance costs of over $20,000 year.

That's one side of the coin.

The other is exemplified by my 78-year-old mother's experience in undergoing a hip arthroplasty operation a few months ago. The operation was successful and my mother, whose mobility and nighttime sleep were impaired by her painful hip, is now getting around without a cane, her pain is gone and she sleeps well.

For her two hours of surgery in a upstate New York community hospital, she was billed $2,300 by her surgeon, another $400 by his partner and $460 by the anesthesiologist, whom she is still hoping to meet. Medicare allowed $1,600 for the operation (Medicaid allows $500 as payment in full for the same procedure) and $170 for the anesthesia, leaving my mother in the bag for about $1,400, had she not had the good sense and wherewithal to purchase ancillary medical insurance coverage.

At $2,300 for a few hours' work, a $20,000 tuition debt or insurance bill ought to shrink pretty fast. With the current economic prospects of medical practice, little wonder that few are frightened away by the costs of medical education.

American medical schools are now more numerous than ever, their enrollments the highest in history. In addition to the 65,000 students enrolled domestically, about 15,000 Americans who couldn't get into U.S. schools are studying medicine abroad, many of them at Caribbean diploma mills.

In New York State, there are more medical schools (12), medical students (6,500) and doctors in training (about 10,000) than any other state in the nation. Even more sobering is the discovery that perhaps 25 to 30 percent of the "offshore" medical students are from the state, including several hundred who are receiving state aid to attend schools in Israel and Puerto Rico.

By the end of this decade, federal and congressional analysts predict the nation will have a physician oversupply ranging between 23,000 to 146,000.In New York, where the ratio of doctors to population exceeds the national average by about 40 percent, the physician concentration is at the point federal analysts foresee for the nation in 1990. Manhattan, for example, enjoys the cozy ratio of one active physician for every 100 or so residents.

Last year, New Yorkers spent about $28 billion on health care, or about $1,600 for every man, woman and child. That figure is well above the national average.

And therein lies a lesson for federal and state policymakers who seek to control the costs of health care. The lesson is that physicians authorize or order about 70 to 80 percent of our health care spending, and the greater the number of physicians we produce, the faster our health care costs will grow -- a complete refutation of the law of supply and demand.

Let me offer several examples of what I mean.

In Manhattan, according to a survey conducted by Dr. Sidney Wolfe, a consumer advocate who used to head the Health Research Group, the prevailing charge by surgeons to Medicare for a prostatectomy was $1,220. Across the river in Queens, where there are far fewer surgeons, the average charge was $775.

Over the past decade, we have witnessed an explosive growth in the number and proportion of Caesarean births, principally because the birth rate is low and the obstetrician supply is high. In New York State, the proportion has grown from 4 percent of live births in 1963 to about 20 percent in 1980. What this means is a longer hospital stay for mother and child, increased risk to both and a doctor's fee about twice that of a normal delivery.

America probably has more heart surgeons than the rest of the world combined. A study at Harvard reported recently in The New England Journal of Medicine suggest that about two-thirds of the 110,000 coronary bypass operations performed each year in the United States are unnecessary, that these patients would do just as well with conservative, less costly medical treatment.

More than a decade ago, when Congress extended Medicare coverage to patients with chronically failed lkidneys, it did so with the understanding that many of these patients would be trained to perfrom dialysis at home, where they could be maintained at about one- third the cost of private and hospital-based dialysis centers. Today, only a handful of patients advance to home dialysis, principally because doctors who own or run the dialysis centers don't want to lose their lucrative fees.

These examples are redolent of G. B. Shaw's observation that "medicine is not a profession; it is a conspiracy."

If federal and state officials hope to succeed in cutting or containing health costs, I believe they must go beyond institutional regulation and the collective mugging of the poor and the elderly, forcing them to pay a greater share of the costs of their care. Efforts must be made to reduce the economic prospects and attractiveness of medical practice, to assure that, as a nation, we have only the number we need and can afford.

As a step in this direction, the federal government should freeze Medicare fees at current levels and require that physicians accept them as payment in full for their services, which, as my mother's experience proves, few physicians do. Failure to comply would result in the physician's disqualification from the Medicare program.

States rich in physicians, such as New York, Massachusetts, California and the District of Columbia, should adopt an imnmediate, five-year moratorium on medical licensure. This would help assure that physicians will practice in states where they are still needed and wanted.

The 5,716 U.S. physicians who have defaulted on their federally guaranteed student loans should not be required to pay up. That would be too easy. Instead, they should be required to work off their indebtedness in doctor-bereft places such as the Bedford-Stuyvesant neighborhood in Brooklyn and the Saint Regis Indian Reservation near Massena, N.Y., at a rate of, say, $200 a week.

The federal government will soon end the captitation aid paid to medical schools for increasing their enrollments. What the government should do instead is to pay grants to schools which significantly decrease enrollment. A special bonus could be paid to schools which follow the lead of the U.S. Energy Department.

A simple way to end or greatly reduce U.S. students' enrollment in inferior foreign medical schools would be to deny them entry into domestic graduate training programs, which would effectively prevent most of them from returning here to practice.

And since what we do today will have little, if any, immediate impact on physician output, we should look for ways to share our bounteous supply of physicians with Third World nations which sorely need them. To foster such sharing, the federal government might offer to pay the costs of passage. One-way, of course.