Thymic extract is made from the thymus gland of cows.
But the claim that taking a combination of bovine thymus hormones can help patients with chronic hepatitis hasn't been proven and rests on shaky scientific ground. The story goes that Dr. Carson B. Burgsteiner, a Savannah, Ga., obstetrician-gynecologist, was an active carrier of hepatitis B and developed a product combining thymic extract with several vitamins, minerals and amino acids that he hoped would have a beneficial effect on his condition. He later reported that the treatment worked and began prescribing the same course of treatment for other disorders, including chronic hepatitis C, rheumatoid arthritis and lupus. They recruited 38 patients with chronic hepatitis C who didn't respond to or couldn't tolerate the side effects of the standard treatment, interferon. After three to six months, they tested the patients and found no benefit from the thymic formula.