Popular sports commentator Clinton Grybas died from a combination of a heart condition and an allergic reaction, his Melbourne radio station says.

Graeme Bond, football director of Fairfax Radio Network station 3AW, said a coroner's report found Grybas died of natural causes.

Mr Bond said the report found Grybas had a faulty heart valve and that he may also have experienced an allergic reaction to something he ate or drank on the night he died.

Grybas, 32, was found dead in his 15th-floor Southbank apartment on January 5 after failing to show up for 3AW's Sports Today program, which began at noon (AEDT) that day.

At the time there was speculation he may have fallen and injured himself while sleepwalking.

Mr Bond said the coroner's report was released to Grybas' immediate family five weeks ago.

He said knowing the cause of Grybas' death didn't lessen the shock.

"It changes nothing. It was an unexpected, tragic death that no one saw coming," Mr Bond told AAP