Dr. Michael F. Holick, Ph.D., M.D., is a globally recognized expert in vitamin D research and metabolic bone health. As a professor of medicine, physiology, and biophysics at Boston University Medical Center, he has made groundbreaking contributions to our understanding of vitamin D's role in human health. Notably, Dr. Holick was the first to identify 25-hydroxyvitamin D3, the major circulating form used to assess vitamin D status, and to isolate and synthesize 1,25-dihydroxyvitamin D3, the active form crucial for treating various bone disorders.