Intern, then resident in internal medicine Yale-New Haven Hospital, 1966-1968. United States Public Health Service research associate National Institute Arthritis and Metabolic Diseases, National Institutes of Health, 1968-1970. Dernham senior fellow oncology University California Medical School, San Francisco, 1970-1972, member faculty, since 1972, professor medicine and biochemistry and biophysics, since 1979, director, Metabolic Research Unit, 1981—2000.
Attending physician University California Medical Center, since 1972. Director endocrine research Howard Hughes Medical Institute, 1976-1981, investigator, 1975-1981. Chief division endocrinology Moffitt Hospital, 1980-1997.
Founder, director California Biotechnology, Inc., 1982-1992. Director, chairman SciClone scientific advisory board, since 1991.
Member American Chemical Society, American Society Hypertension, American Society Clinical Investigation, American Thyroid Association, Association American Physicians, American Federation Clinical Research, Endocrine Society, president, 2002-2003, Western Association Physicians, Western Society Clinical Research, Institute Medicine, National Academy of Sciences.