MERCK and Co's "hair raising"research involves Proscar, itsexperimental prostate shrinking drug, which holds out a promise ofgreening the bald heads of men.Scientists believe Proscar mightgrow hair by blocking the formation of the malehormone dihydrotestosterone.People born with reduced levels ofthis hormone are rarely bald. Proscar apparently shrinks enlargedprostates by blocking the formationof the same hormone.