Democratic presidential front-runner Hillary Clinton was reported to have had a massive coughing fit while delivering a speech on Monday, raising fresh doubts on her state of health a week before the Iowa caucuses, the start of the nearly year-long U.S. election process.

The 68-year-old Clinton had to stop talking to her audience in West Des Moines, Iowa, as she endured the coughing spell, WND reported.

"@HillaryClinton has coughing attack at West Des Moines event, may be unable to finish remarks," Amy Chozick of the New York Times said on Twitter.

Clinton's health has been a cause for worry since her last coughing fit before the House Select Committee on Benghazi on Oct. 22, 2015. Media titan Matt Drudge even called Clinton's apparent health issues as the "biggest revelation" of the Benghazi hearings.

"Hillary health was biggest revelation at hearing. Coughing fit. Slow-speaking, obviously induced by meds. Choose not to believe if you must," Drudge tweeted.

In a statement issued last July, Clinton's campaign confirmed that the former State secretary is suffering from hypothyroidism and allergies, adding that she is taking medication to treat an underactive thyroid.

The medication, called Armour Thyroid, can also be used to prevent certain types of enlarged thyroid glands and to manage thyroid cancer, Fox News reported last July 31.

Clinton also sustained a concussion after falling inside her home in December 2012. She was given blood thinners for a blood clot in her head and returned to work on Jan. 7, 2013.

The top Democratic presidential aspirant recently laughed off a question by an Iowa voter who asked if she "was really not equipped to be in the White House" because of health issues.

"Oh my. Well, you know, they say nearly anything about me. I've got to tell you," Clinton, said, ABC News reported Saturday. "There are several themes they keep beating the drums on. I'll match my endurance against anybody."