The pop superstar was told by doctors when he was in his 30s that his levels of the male sex hormone were equivalent to those of an ''80-year-old man'' after he sought medical help for his depression.
The 'Angel' singer was put on a course of testosterone injections to provide him with a normal level of the hormone, and Ayda says the medication transformed her husband's life.
Speaking on UK TV show 'Loose Women' on Monday, she said: ''Robbie suffered with low testosterone, and for some men it means a loss of libido, but it was nothing to do with that for him. He had lethargy and depression. He actually didn't know, and we got his blood panels done and he they said he had the testosterone of an 80-year-old man. He was in his 30s at the time. I think he was surprised ... The minute he took the testosterone he felt as though he had a new lease on life, he could do things, he was happy, he was motivated and it had nothing to do with getting big muscles.''
Ayda - who has two children, daughter Teddy - admits she was worried that Robbie, 44, might have felt emasculated by the diagnosis, but when he decided to go public with it she was super proud of him for being so honest with his fans.
She said: ''It was probably a bit emasculating but I didn't really want to circle on that, I didn't want to go, 'Do you feel like less of a man?' Look, why should a man in his 30s have the testosterone levels of an 80-year-old man?
''There's this thing with men where they're not allowed to talk about these things, I'm so proud of him because he's always so open about his struggles.''
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