UTRECHT, Netherlands (Reuters) - Dutchman Lars Boom started the Tour de France on Saturday despite showing low levels of cortisol in a test on the eve of the race.
Low levels of the hormone can be explained by the use of corticoids, anti-inflammatory drugs that are allowed out of competition but forbidden while racing unless a rider is granted a Therapeutic Use Exemption (TUE).
Boom had an outside chance of victory in Saturday's 13.8-km time trial but eventually finished 23rd, 44 seconds behind winner Rohan Dennis of Australia.
"I did not have the best preparation," Astana rider Boom told reporters.
Astana, the team of defending Tour champion Vincenzo Nibali, are members of the MPCC (Movement for Credible Cycling) that applies stricter rules than the International Cycling Union (UCI) and the World Anti-Doping Agency (WADA).
Under MPCC rules Boom should have rested for eight days but UCI regulations, by contrast, do not forbid him from racing.
UCI president Brian Cookson said the rider had not broken any anti-doping rule.
"No rules of the UCI and the World Anti-Doping Agency have been broken so he's allowed to ride the Tour de France," added Cookson.
"No anti-doping rules have been broken in this case. Low cortisol levels in themselves are not proof of an anti-doping violation."
The team's bid to replace Boom with Italian Alessandro Vanotti was turned down by the UCI who said on Friday that their request was made too late.
"Astana ... received confirmation from the UCI that as a low cortisol result is no risk to the health of the rider...there are no valid grounds for a late substitution," the Kazakh-funded team explained in a statement.
"Team medical staff have advised that Boom's low cortisol result is the consequence of a long-standing and well-known application of anti-asthma therapy by the athlete and is not a violation of UCI rules and regulations.
"Team medical staff have advised there is no danger to the rider's health or safety to start the 2015 Tour de France."
Astana are no strangers to controversy, having come close to losing their World Tour license this year following positive tests from Kazakh riders in the team.
Editing by John O'Brien