BEGINNING this spring, up to 400 men in countries around the world will begin to test a synthetic form of the male hormone testosterone as a form of birth control. Researchers hope the use of the hormone for contraception will one day rival the condom in effectiveness and acceptance.
In the first clinical testing of the method, the men will receive the injections once a week for a year. Unlike in previous tests, they would use the injections as their sole source of birth control.
Dr. C. Alvin Paulsen, a professor of medicine at the University of Washington in Seattle, has been testing the method in the laboratory and on animals since 1972. The new tests will be conducted in the United States, England, China and other developed and developing nations selected by the World Health Organization, an agency of the United Nations. In the United States, the test will be performed on 30 men in Seattle.
The process of sperm production is complex. Normally, the amount of testosterone in the blood regulates the release by the pituitary gland of two additional hormones: one, called luteinizing hormone, stimulates the production of more testosterone. The other, called follicle-stimulating hormone, facilitates production of sperm. The researchers reason that if testosterone were maintained at a high level, the pituitary would not be signalled to produce the hormones needed to make testosterone, and the testes would stop producing sperm.
Although testosterone is used for treatment of other problems, such as infertility, Dr. Paulsen cautioned that its use as a contraceptive would have to be tested for several years. For example, he said, the prostate gland is stimulated by testosterone and doctors want to see if it is adversely affected by the injections of the synthetic substance, testosterone enanthate. Tests so far have not shown any effects on sex drive or other personality factors, he said.
''When you consider that we haven't had a new method of male contraception in more than 200 years, since the condom was invented, we're going pretty fast,'' he said. Dr. Paulsen, who is also director of the Population Center for Research in Reproduction, added: ''If a man could drop by a clinic and get an injection once every three months or so, then that's within the realm of the practical.'' Sperm Production Resumes
If the tests are successful, researchers believe the injections would be more effective than the condom and a useful alternative to vasectomies, which are not usually reversible. In previous testing, normal sperm production resumes shortly after the injections are stopped. However, the injections do not offer protection against sexually transmitted diseases such as AIDS.
The immediate goal, as outlined by the W.H.O., is to match or improve upon the condom's failure rate.
''I think what we're looking at is something that could eventually be 100 percent effective,'' said Dr. William Bremner, a member of the W.H.O. advisory committee that will monitor the tests.
Recent studies by the Food and Drug Administration listed the condom as having a failure rate of 17 percent; that is, 17 women in every 100 couples using no other birth control method became pregnant. Scientists at W.H.O. list a condom failure rate of 5 to 10 percent.
The F.D.A. said the diaphragm had a failure rate of 18 percent; vaginal foam 25 percent; the rhythm method 40 percent. The lowest rate was the birth control pill for women; fewer than 1 percent of its users became pregnant. #15 Years of Testing Scientists involved in the hormone tests by Dr. Paulsen said they were cautiously optimistic that they could eventually refine the dose to produce a failure rate below 1 percent.
In 15 years of testing of safety and dosage, University of Washington researchers have found that weekly hormone injections brought the sperm count down to zero in about 60 percent of the 500 volunteers, all of whom were tested weekly.
Researchers are still unsure what dosage will produce a sperm count of zero or a level considered low enough to prevent pregnancy. Typically, there are 40 million to 200 million sperm per milliliter of semen.
In the first phase of Dr. Paulsen's test, each man will get the same weekly dose of injected testosterone. Then, the men with a sperm count of zero will be separated from the other subjects and asked to use the injections as their only source of birth control. The other men would be studied for the effect of the injections on sperm count only. Work on Another Compound
''From there we can hopefully go on to developing a product for the consumer,'' said Dr. Paulsen. ''But if the failure rate is not below that of the condom, we're done - because it would be of little benefit to society.''
One problem is with the hormone itself. To work, the testosterone must be injected weekly to maintain the hormone level. It would be impractical, scientists say, to expect most men to take injections every week.
To get around that, W.H.O. researchers led by Dr. Gabriel Bialy at the National Institutes of Health center in Bethesda, Md., have been working with another synthetic testosterone that would be injected once every three months.
Dr. Paulsen said he has had no trouble finding volunteers for the tests. ''You'd be surprised at how many people out there are deeply interested in finding a new method,'' he said.
Several years ago, ago, a W.H.O. task force estimated that up to 75 percent of men would interested in such a method, if it was safe and practical.