Dr. Yamaguchi graduated from Shizuoka College of Pharmacy (B.S.) in 1971 and obtained Ph.D of Pharmaceutical Sciences in 1976. He was engaged as Research Associate and Assistant Professor in Shizuoka College of Pharmacy (1973-1987). As Assistant Professor in School of Pharmaceutical Sciences, University of Shizuoka(1987-1991). As Associated Professor in University of Shizuoka, Graduate School of Nutritional Sciences (1991-1993) and Professor in University of Shizuoka, Graduate School of Nutritional Sciences (1993 ~ 2007) in Japan. From 2007, Yamaguchi was invited as Visiting Professor, Emory University School of Medicine, Department of Medicine. He was appointed Editorial Board Member of many Journals including International Journal of Molecular Medicine, Molecular Medicine Reports, Journal of Osteoporosis, International Journal of Medicine and Medical Sciences, International Journal of Nutrition and Metabolism, Molecular and Cellular Biochemistry, Endocrinology Studies, Alternative Medicine Studies, Experimental and Therapeutic Medicine, and Stem Cell Discovery. Yamaguchi published over 500 English original papers, review articles and books.

Dr. Yamaguchi's research fields include the bone and calcium endocrinology and metabolism, nutritional prevention of osteoporosis, and the exploration of intracellular signaling mechanism. Yamaguchi found the novel protein and genes which were named as Regucalcin and RGPR-p117.