In 1978, University of California, Berkeley (UC-Berkeley) scientist Choh Hao Li discovers Beta-endorphin, a substance produced in the brain that acts as a pain killer. Li was either the first or among the first to isolate and identify the anterior pituitary hormones.

The initial breakthrough came in 1940 when he isolated luteinizing hormone. ACTH was the first hormone to be chemically identified and partially synthesized. It took 32 years of research for Li to synthesize the human growth hormone. The identification, purification and later synthesis of human growth hormone and the identification of beta-endorphin were his two most widely recognized achievements. His last accomplishment was the identification and purification of insulin-like growth factor I.