WASHINGTON, Sept 10 (Reuters) - NPS Pharmaceuticals Inc's hormone replacement therapy Natpara reduced the need for calcium and vitamin D supplements in clinical trials, though data from one trial site was excluded due to manufacturing violations, according to a preliminary review by the U.S. Food and Drug Administration.

The report, posted on Wednesday on the FDA's website, comes two days ahead of a meeting of outside advisers to the agency who will discuss the drug and recommend whether it should be approved. The FDA reviewers said serious adverse events were similar between the treatment group and the placebo group.

Natpara is designed to treat hypoparathyroidism, a condition in which the body's parathyroid gland does not secrete enough parathyroid hormone (PTH). The hormone works with vitamin D to regulate body calcium.

(Reporting by Toni Clarke; Editing by Susan Heavey)