The greatest threat to Justin Bieber's career may not be lawsuits, piracy or Willow Smith – but puberty. The 16-year-old's voice is dropping, according to reports, and his label is offering him "vocal conditioning".

Bieber's fans first noticed his vocal troubles in November, during the singer's shaky performance of Pray at the American Music awards. Since then, label boss LA Reid has stepped in by hiring Jan Smith, the vocal coach who helped Bieber's mentor, Usher, in the early-90s. "She has me doing vocal ... exercises regularly," Bieber said.

This obviously is not the first time a teen star's voice has cracked. More than a decade ago, it was Usher who was struggling with his upper range – and it almost ruined him. "Losing my voice fucked me up," Usher recently told the Hollywood Reporter. His label – Island Def Jam, which now represents Bieber – was far from sympathetic. "[I] lost it," admitted Reid. "I heard [Usher] at a showcase, and he couldn't sing. I was embarrassed. It was like: 'Damn, where's the voice? What happened to his tone? Where's the power and the range?' It was all gone. I wanted to drop him. I wanted to be out of business with him. I broke his heart. I broke his mother's heart. It was a very tough period in both our lives."

Thankfully for Usher, Diddy – then known as Puff Daddy – stepped in and told Reid not to "be a fool". "[He said,] 'Don't sell your stock in Usher,'" Reid said. "'He's still going to be a star. He's everything you thought he was the day you signed him.'" Reid's patience has since reaped its rewards – Usher remains a huge star – and the label boss is applying the same attitude to Bieber's pubescent troubles. "I know how to be encouraging now," Reid said. "Puffy was right."

For the moment, Bieber is promoting his new 3D movie, Never Say Never, which opens today. "I'm not just some packaged thing that some A&R put together," he told MTV News. "I'm just a regular 16-year-old having fun, just living my dream." But he's also a 16-year-old with millions of fans. As The-Dream put it, describing the sound of Bieber's new material, Justin is "somewhere between Fergie and Jesus". Even Jesus Christ's voice had to break some time.