DASHING Melbourne defender Christian Salem has been moved to a modified training program due to a thyroid issue.

There has been no timeframe given for his return to the main group, and it is a concern that has occurred twice in his nine years on Melbourne's list.

The thyroid gland helps controls body temperature, heart rate, blood pressure and weight.

Salem lost six kilograms during a flare-up just after he was drafted in late 2013, and in 2016 didn't return to the senior side until round 23 after a re-emergence of the issue following round eight.

Christian Salem kicks the ball during Melbourne's clash against Brisbane in round 15, 2022. Picture: AFL Photos

"Christian is currently undergoing treatment for an illness resulted to his thyroid gland," Melbourne's head of medical Dr Laura Lallanec said.

"Christian has had a similar issue in the past where his thyroid becomes overactive.

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"He will continue to be monitored closely by his specialist and reintegrate into training as his thyroid levels stabilise."

Salem had a stellar 2021 campaign, named in the All-Australian squad of 40 as the Demons broke through for a long-awaited premiership, but missed nearly three months in the first half of last season due to a knee injury sustained in round one.