4-PREGNEN-17-OL-3, 20-DIONE 21-ALDEHYDE HEMIACETAL from Steraloids. For over 60 years, we've supplied the finest research institutions, pharmaceutical companies, and law enforcement agencies with over 2,700 different androgens, estrogens, cholestins, progestins, bileacids, hormones, and metabolites synthesized to purified standards for purposes of research.