Dr. David Kleinberg's laboratory has a long-standing and productive interest in control of mammary gland development. He and his group were responsible for demonstrating that growth hormone and prolactin are separate molecules in human beings, and that prolactin is an important hormone in clinical endocrine disorders, such as pituitary tumors. They then went on to demonstrate that mammary development was importantly controlled by growth hormone and IGF-1, while the role of prolactin was mainly that of lactogenesis. Recently, prostate development has also been shown to depend on growth hormone and IGF-1. Dr. Kleinberg's work has been continuously funded by NIH, the Veteran's Administration, or DOD.