IGF-1 (Insulin-Like Growth Factor) is a small polypeptide that plays a critical role in the proper regulation of adult cellular growth in almost all tissue types.* NOW® IGF-1 is extracted from New Zealand deer antler velvet. Competitive athletes who are regularly tested should check with their sanctioning body for the status of this supplement. ng is the abbreviation for nanograms (1 billionth of a gram). Natural color variation may occur in this product.