Ornithine can be made from arginine, and it in turn can proceed to form glutamic acid, citrulline, and arginine and further to proline and hydroxyproline. With arginine, ornithine is useful in nitrogen (ammonia) metabolism. It has been described as a stimulant for growth hormone release and is thought to help build the immune system, promote wound healing, and support liver regeneration. People who are poorly nourished or who lack protein in their diet may be deficient. Ornithine is usually supplemented along with arginine, as they have similar actions. The most common use is in body builders as a growth hormone stimulant. A dose of 1500–2500 mg. twice daily is required for this type of effect. Side effects might include insomnia.