Senator Charles E. Grassley wrote to 10 top medical schools Tuesday to ask what they are doing about professors who put their names on ghostwritten articles in medical journals  and why that practice was any different from plagiarism by students.

Mr. Grassley, of Iowa, the ranking Republican on the Senate Finance Committee, sent the letters as part of his continuing investigation of so-called medical ghostwriting. The term refers to publication of medical journal articles in which an outside writer  sometimes paid by a drug or medical devices company whose product is being studied  has done extensive work on the article without being named on the publication. Instead, one or more academic researchers may receive author credit.

Mr. Grassley said ghostwriting had hurt patients and raised costs for taxpayers because it used prestigious academic names to promote medical products and treatments that might be expensive or less effective than viable alternatives.

“Any attempt to manipulate the scientific literature, which can in turn mislead doctors to prescribe treatments that may be ineffective and/or cause harm to their patients, is very troubling,” the senator wrote.