Allegations of industry-sponsored ghostwriting date back at least a decade, to scientific articles about fen-phen, the diet drug combination that was taken off the market in 1997 amid concerns that it could cause heart-valve damage. But evidence of the breadth of the practice has come to light only gradually, most recently in documents released in litigation over menopause drugs made by Wyeth.

The documents offer a look at the inner workings of DesignWrite, a medical writing company hired by Wyeth to prepare an estimated 60 articles favorable to its hormone drugs. In one publication plan, for example, DesignWrite wrote that the goal of the Wyeth articles was to de-emphasize the risk of breast cancer associated with hormone drugs, promote the drugs as beneficial and blunt competing drugs. The articles were published in medical journals between 1998 and 2005  continuing even though a big federal study was suspended in 2002 after researchers found that menopausal women who took certain hormones had an increased risk of invasive breast cancer and heart disease.

Wyeth has changed its policy in the years since the hormone papers were published, according to Douglas Petkus, a company spokesman, and now requires that scientific articles acknowledge any participation by Wyeth or a Wyeth-sponsored writer. Some leading medical journals have also beefed up their disclosure policies for authors.

Some of the authors of the Wyeth hormone articles played significant roles in the work, while others made minor changes to drafts that were prepared for them, the documents show. But, in the main, the articles did not disclose that they had been drafted by outside writers paid to advance the drug company’s views.

Many universities have been slow to react to evidence about the extent of the practice. In December, for example, Mr. Grassley released documents indicating that DesignWrite had drafted an article that was published under the name of a gynecology professor at New York University School of Medicine.

Eight months later, a spokeswoman said the school had not looked into the matter.

“If we had received a complaint, we would have investigated,” said Deborah Bohren, the vice president for public affairs at New York University Langone Medical Center. “But we have not received a complaint.”

She added N.Y.U. never condoned ghostwriting and was now drafting a written policy to that effect. Faculty members, however, are responsible for the integrity of their own work, she said.