The study was stopped early because of a cancer scare resulting from other Lilly research in which scientists found that rats developed bone cancer when given high lifelong doses of the drug. However, researchers eventually decided that the results do not suggest a higher cancer risk in people. Among other things, people with naturally high levels of the hormone as a result of overactive parathyroid glands are not especially prone to bone cancer, and none of the women in this or earlier studies of the hormone has developed the cancer. The entire parathyroid hormone contains 84 amino acids. Forteo is a 34-amino acid portion of this.
Experts believe it does the same job as the full hormone.