Newly unveiled court documents show that ghostwriters paid by a pharmaceutical company played a major role in producing 26 scientific papers backing the use of hormone replacement therapy in women, suggesting that the level of hidden industry influence on medical literature is broader than previously known.

The articles, published in medical journals between 1998 and 2005, emphasized the benefits and deemphasized the risks of taking hormones to protect against maladies like aging skin, heart disease, and dementia. That supposed medical consensus benefited Wyeth, the pharmaceutical company that paid a medical communications firm to draft the papers, as sales of its hormone drugs, called Premarin and Prempro, soared to nearly $2 billion in 2001.

But the seeming consensus fell apart in 2002 when a huge federal study on hormone therapy was stopped after researchers found that menopausal women who took certain hormones had an increased risk of invasive breast cancer, heart disease, and stroke. A later study found that hormones increased the risk of dementia in older patients.

The ghostwritten papers were typically review articles, in which an author weighs a large body of medical research and offers a bottom-line judgment about how to treat a particular ailment. The articles appeared in 18 medical journals, including The American Journal of Obstetrics and Gynecology, and The International Journal of Cardiology.

The articles did not disclose Wyeth’s role in initiating and paying for the work. Elsevier , the publisher of some of the journals, said it was disturbed by the allegations of ghostwriting and would investigate.

The documents on ghostwriting were uncovered by lawyers suing Wyeth and were made public after a request in court from PLoS Medicine, a medical journal from the Public Library of Science, and The New York Times.

A spokesman for Wyeth said that the articles were scientifically accurate and that pharmaceutical companies routinely hired medical writing companies to assist authors in drafting manuscripts.

The court documents provide a detailed paper trail showing how Wyeth contracted with a medical communications company to outline articles, draft them, and then solicit top physicians to sign their names, even though many of the doctors contributed little or no writing. The documents suggest the practice went well beyond the case of Wyeth and hormone therapy, involving numerous drugs from other pharmaceutical companies.

“It’s almost like steroids and baseball,’’ said Dr. Joseph S. Ross, an assistant professor of geriatrics at Mount Sinai School of Medicine in New York, who has conducted research on ghostwriting. “You don’t know who was using and who wasn’t; you don’t know which articles are tainted and which aren’t.’’

Because physicians rely on medical literature, the concern about ghostwriting is that doctors might change their prescribing habits after reading certain articles, unaware they were commissioned by a drug company.

Wyeth faces 8,400 lawsuits from women who claim that the company’s hormone drugs caused them to develop illnesses.

© Copyright 2009 Globe Newspaper Company.