A teenager named Dean was in an Iowa jail for a week when he pulled loose the nylon drawstring from a jacket, threaded one end through a ventilation grille in his cell, knotted the other end around his throat, then let his knees collapse. Before he killed himself, Dean penciled a message on the cell wall. "I ain't ready to die. Help me die." Dean's crime was that he was a runaway.

Yesterday, George P. Belitsos, director of Youth and Shelter Services, Inc., insumes, Iowa, told a Senate sub-committee that Dean's jail suicide "makes the need for alternatives" to jails for runaways who have not committed crimes "tragically clear."

Since the Iowa shelter house was founded five years ago, said Belitors, 1,200 clients much like Dean have been aided in a program that provides temporary shelter, family counseling and residential home alternatives to jail.

The Senate Subcommittee to Investigate Juvenile Delinquency held hearings yesterday in an attempt to see how well the Juvenile Justice and Delinquency Prevention Act of 1974 is being implemented. The act gives federal funds to states to improve their juvenile justice systems on the condition that states cease locking up juvennile "status offenders" - runaways, truants and neglected teenagers in need of supervision who have not committed any crime.

Progress toward creating alternatives to jail was "spotty, at best," said Sen. John Culver (D-Iowa), subcommittee chairman. He said it would take time to change years of practice. He pointed to the Iowa shelter homes and other experiments around the country as proof that fundamental changes in the treatment of status offenders and juvenile delinquents can be made.

Dr. Karl A. Menninger, the well known psychiatrist, who is head of the Menninger Foundation and The Villages, Inc., testified that 13 years ago he started "villages" where "surrogate parents" live with 10 children at a time. It was costly, but, he said, out of 152 who have lived in one village, only three have been jailed as adults.

Many testified yesterday that the status offender should be excluded from the juvenile justice system entirely. A Tucson juvenile court judge, John P. Collins, said the youth court system "destroys and impairs at least as many as it helps."

One major problem is funding for alternative programs. Another problem is fighting a pervasive attitude. Menninger said, that institutionalizing is still the best way to treat juveniles who are unwanted at home or who are runaways or who have committed petty crimes.

"The attitude goes, "if we make them suffer a little longer, they'll grow better." They don't. They become tomorrow's adult criminals," Menninger said.