In an interview from his Park Avenue office, Dr. Harold Bornstein said he hastily wrote the letter, but defended his over-the-top wording, telling NBC Newsthat he "picked up [Trump's] kind of language" as he wrote.
"I thought about it all day, and at the end I get rushed and I get anxious when I get rushed, so I tried to get four or five lines done as fast as possible," Bornstein said of his writing process.
Bornstein's letter, released to the public in December, has again gained attention in recent days, as Trump and his surrogates have touted conspiracy theories about Hillary Clinton's health.
MSNBC's Rachel Maddow asked Trump's new campaign manager Kellyanne Conway in an interview earlier this week — after Trump pushed unsubstantiated rumors about Clinton's health — whether Trump should release a more serious health letter.
"As a doctor's letter, it's a little bit absurd. It's a non-serious letter," Maddow said, according to a transcript from MSNBC. "It's full of typos. It's hyperbolic. It's unprofessional. Most of the letter has no medical meaning."
Conway responded with a simple, "perhaps," adding that she did not want to comment on Clinton's health.
RELATED: See images of Trump and Pence on the campaign trail
Donald Trump and Mike Pence on the campaign trail since the RNC
Donald Trump and Mike Pence on the campaign trail since the RNC
Republican presidential nominee Donald Trump arrives for a rally at Duplin County Events Center in Kenansville, North Carolina on September 20, 2016. / AFP / MANDEL NGAN (Photo credit should read MANDEL NGAN/AFP/Getty Images)
ESTERO, FL - SEPTEMBER 19: Republican presidential candidate Donald Trump speaks during a campaign rally at the Germain Arena on September 19, 2016 in Estero, Florida. Trump is locked in a tight race against Democratic candidate Hillary Clinton in Florida as the November 8th election nears. (Photo by Joe Raedle/Getty Images)
Republican presidential nominee Donald Trump speaks during a rally at the JetCenters of Colorado in Colorado Springs, Colorado on September 17, 2016. / AFP / MANDEL NGAN (Photo credit should read MANDEL NGAN/AFP/Getty Images)
THE TONIGHT SHOW STARRING JIMMY FALLON -- Episode 0534 -- Pictured: (l-r) Republican Presidential Candidate Donald Trump during an interview with host Jimmy Fallon on September 15, 2016 -- (Photo by: Andrew Lipovsky/NBC/NBCU Photo Bank via Getty Images)
Republican presidential nominee Donald Trump speaks at the Bethel United Methedoist Church on September 14, 2016 in Flint, Michigan. / AFP / MANDEL NGAN (Photo credit should read MANDEL NGAN/AFP/Getty Images)
WASHINGTON, DC - SEPTEMBER 13: U.S. Republican vice presidental nominee Gov. Mike Pence addresses a news conference with House GOP leaders following a conference at Republican headquaters on Capitol Hill September 13, 2016 in Washington, DC. When asked about former vice presidential candidate Speaker Paul Ryan's reluctance to endorse presidential candidate Donald Trump, Pence said that the House Republicans and the campaign agree on a plan for America. (Photo by Chip Somodevilla/Getty Images)
Donald Trump, 2016 Republican presidential nominee, greets attendees after speaking at a campaign event in Des Moines, Iowa, U.S., on Tuesday, Sept. 13, 2016. Any path Trump might take to the presidency inevitably leads through the Rust Belt and industrial Midwest the places the Republican nominee describes as 'rusting and rotting' war zones of manufacturing decline. Photographer: Daniel Acker/Bloomberg via Getty Images
NEW YORK, NY - SEPTEMBER 12: (L-R) Chairman and CEO of Cantor Fitzgerald, Howard Lutnick, US Republican presidential nominee Donald Trump, and Executive Managing Director, North America for BGC, Daniel LaVecchia attend Annual Charity Day hosted by Cantor Fitzgerald, BGC and GFI at BGC Partners, INC on September 12, 2016 in New York City. (Photo by Larry Busacca/Getty Images for Cantor Fitzgerald)
AKRON, OH - AUGUST 22: Republican Presidential candidate Donald Trump addresses supporters at the James A. Rhodes Arena on August 22, 2016 in Akron, Ohio. Trump currently trails Democratic Presidential candidate Hillary Clinton in Ohio, a state which is critical to his election bid. (Photo by Angelo Merendino/Getty Images)
FREDERICKSBURG, VA - AUGUST 20: GOP nominee Donald Trump holds a rally in Fredricksburg, VA on August 20, 2016 in Fredericksburg, Virginia. (Photo by Leigh Vogel/WireImage)
US Republican Presidential candidate Donald Trump addresses supporters at the Summit Sports and Ice Complex on August 19, 2016 in Diamondale, Michigan. / AFP / JEFF KOWALSKY (Photo credit should read JEFF KOWALSKY/AFP/Getty Images)
Donald Trump, 2016 Republican presidential nominee, pauses while speaking during a campaign rally at the Erie Insurance Arena in Erie, Pennsylvania, U.S., on Friday, Aug. 12, 2016. Two days after Trump said that President Barack Obama had founded Islamic State, and a day after he insisted that he meant what he said, the Republican presidential nominee reversed himself on Friday and claimed the statement was nothing more than sarcasm. Photographer: Ty Wright/Bloomberg via Getty Images
Donald Trump, 2016 Republican presidential nominee, speaks during a campaign rally at the Erie Insurance Arena in Erie, Pennsylvania, U.S., on Friday, Aug. 12, 2016. Two days after Trump said that President Barack Obama had founded Islamic State, and a day after he insisted that he meant what he said, the Republican presidential nominee reversed himself on Friday and claimed the statement was nothing more than sarcasm. Photographer: Ty Wright/Bloomberg via Getty Images
SUNRISE, FL - AUGUST 10: Republican presidential candidate Donald J.Trump addresses the audience during a campaign event at BB&T Center on August 10th, 2016 in Sunrise, Florida. (Photo by Johnny Louis/WireImage)
WILMINGTON, NC - AUGUST 9: Republican presidential candidate Donald Trump shakes hands with supporters during a campaign event at Trask Coliseum on August 9, 2016 in Wilmington, North Carolina. This was TrumpÃs first visit to Southeastern North Carolina since he entered the presidential race. (Photo by Sara D. Davis/Getty Images)
Donald Trump, 2016 Republican presidential nominee, is seen on a monitor speaking during an event to discuss his economic plans at the Detroit Economic Club in Detroit, Michigan, U.S., on Monday, Aug. 8, 2016. Trump is promising the biggest overhaul to the personal income-tax code since Ronald Reagan, as well as a deep cut in the corporate tax rate. He's also pledging to end excessive regulation and lift restrictions on the nation's energy producers. Photographer: Sean Proctor/Bloomberg via Getty Images
PORTLAND, ME - AUGUST 4: Presidential candidate Donald Trump shakes hands with Maine Gov. Paul LePage being introduced at a rally in Merrill Auditorium on Thursday, August 4, 2016. (Photo by Derek Davis/Portland Press Herald via Getty Images)
COLORADO SPRINGS, CO - JULY 29: Republican presidential nominee Donald Trump waves to supporters after his speech at the Gallogly Event Center on the campus of the University of Colorado on July 29, 2016 in Colorado Springs, Colorado. (Photo by Joe Mahoney/Getty Images)
SCRANTON, PA - JULY 27: Republican presidential candidate Donald Trump speaks to a crowd of supporters on July 27, 2016 in Scranton, Pennsylvania. Trump spoke at the Lackawanna College Student Union Gymnasium. (Photo by John Moore/Getty Images)
DORAL, FL - JULY 27: Republican presidential candidate Donald Trump holds a press conference at Trump National Doral on July 27, 2016 in Doral, Florida. Trump spoke about the Democratic Convention and called on Russia to find Hillary Clinton's deleted e-mails. (Photo by Gustavo Caballero/Getty Images)
Donald Trump, the Republican presidential nominee, waves to the crowd after addressing the 117th annual VFW National Convention at the Charlotte Convention Center on Tuesday, July 26, 2016. (David T. Foster III/Charlotte Observer/TNS via Getty Images)
CHARLOTTE, NC - JULY 26: Republican vice presidential candidate, Indiana Gov. Mike Pence speaks as Republican presidential candidate Donald Trump looks on at the 117th National Convention of the Veterans of Foreign Wars of the United States as veterans strive for a photo at the Charlotte Convention Center on July 26, 2016 in Charlotte, North Carolina. One day after Democrat presidential candidate Hillary Clinton faced the same group, Trump promised a revision to health care for veterans. (Photo by Sara D. Davis/Getty Images)