Brennan, who won gold in the single skulls at the Rio Olympics, was one of 11 athletes whose medical data was leaked on Friday by a Russian hacking group, which is known as APT28 and Fancy Bear by US cyber-security researchers.
The documents leaked included details of a Therapeutic Use Exemption (TUE) granted to Brennan after she was administered adrenalin in a hospital emergency room following a severe allergic reaction in January 2014, Rowing Australia said in a statement.
The TUE authorises her to carry an EpiPen, the lifesaving allergy treatment.
Russian President Vladimir Putin said on Friday that the leaked records "raised a lot of questions" with healthy athletes seemingly taking banned substances.
"To call into question the use of a substance administered by a doctor in a hospital emergency department to combat a severe allergic reaction is beyond disappointing," Brennan said.
"This administration of adrenaline was in no way performance enhancing. I was seriously ill following this hospitalisation and I am upset I have to justify in the public domain my personal medical records."
The documents, which were held by the World Anti-Doping Agency (WADA), were the third tranche of records to be leaked by the hackers this week.
The other Australian rower whose records were leaked on Friday, Rio silver medallist Alexander "Sasha" Belonogoff, also carries an EpiPen because of a food allergy, Rowing Australia said.
The governing body joined the Australian Sports Anti-Doping Authority (ASADA) in condemning the "malicious attacks by Fancy Bears and their blatant disregard for athlete privacy and well-being".
"We at Rowing Australia back the two rowers named as absolutely clean and having abided by ASADA's rules," said Rowing Australia medical officer Professor Peter Fricker.
"A TUE is granted for therapeutic purposes only and not for performance enhancement."
WADA considers the attacks are being carried out as retaliation for the agency's investigations that exposed state-sponsored doping in Russia and led to almost the entire track and field team being banned from last month's Olympics.
Russia was also banned from sending a team to the Paralympics.
WADA has said it believes the hackers gained access to itsanti-doping administration and management system (ADAMS) via anIOC-created account for the Rio Games.
"I followed all WADA procedures in ensuring I received the appropriate permissions for this treatment and strongly believe in doping free sport," Brennan added.
"The highly concerning issue here is the leak of personal medical information."
Image: Australian rower Kim Brennan poses with her gold medal at the Rio Olympics
Photograph: Carlos Barria/Reuters