Ronald Eugene Nollet, 53, and his son, Ronald Nollet Jr., 31, pleaded guilty in San Diego on Tuesday to federal charges of counterfeiting Serostim, a costly human growth hormone used by some HIV-positive people to combat AIDS-related wasting. The pair admitted to ordering 6,000 vials of a similar, much cheaper medication from an Oregon firm that did not include somatropin, the active ingredient used in Serostim. They then labeled the vials to falsely indicate that the product was manufactured by Serono Laboratories, the Massachusetts firm that markets Serostim. Authorities seized several hundred of the 6,000 counterfeit Serostim vials the Nollets ordered in April and intercepted a second batch the men ordered in July. Each of the men faces up to three years in prison when sentenced in January.