Teen Mom 2" Cast The Season 5 cast of MTV's "Teen Mom 2," from left, Jenelle Evans, Chelsea Houska, Kailyn Lowry and Leah Calvert Photo: MTV/TeenMom2

It appears “Teen Mom 2” just lost one of its leading cast members. Longtime star Leah Calvert announced to her fans on social media Friday that she will not be returning for the MTV program’s sixth season. The network has yet to confirm the mom of three is leaving.

"Are you doing Season 6?" one viewer tweeted to Leah Friday. The reality-TV star replied with a shocker: "No." Following her bombshell announcement, the 22-year-old "Teen Mom 2" star elaborated on her departure after one viewer speculated that the rest of the cast, Jenelle Evans, Kailyn Lowry and Chelsea Houska, would also not return for another installment of the reality-TV program.

“If @TM2LeahDawn isn’t doing Season 6… That probably means none of them are,” said the viewer. After Leah’s former co-star Jenelle told the fan not to “assume” anything, Leah responded, confirming her fate. “I hope my girls continue to move on with TM2,” she said. “I wish them the BEST xoxo.”

Fans later expressed their consternation over Leah’s departure, claiming the show “wouldn’t be the same” without her. Leah attempted to console her fans, saying, “I’m sorry! My girls still do what they do and keep things going!”

Leah later suggested that parting ways with MTV was the best choice for her children, Adalynn, 1, with her husband Jeremy Calvert, and her 4-year-old twins Ali and Aleeah, with her ex-husband, Corey Simms. “I will miss you on TM2 but you know the right for your family. God bless u and the 3 amazing little girls you have,” one fan posted, a message which Leah retweeted to her followers Friday.

The casting shakeup comes two weeks after InTouch Weekly reported that MTV was planning to send Leah to a rehab facility to treat her alleged drug issues. Last month, the Ashley’s Reality Roundup reported that Leah’s alleged drug use and marital issues with Jeremy were causing a Season 6 filming delay. According to the site's report, as of Oct. 22, the couple were the only “Teen Mom 2” cast members who had yet to return their contracts to the network.

Leah is the second of MTV’s teen moms to part ways with the long-standing series. In August, MTV confirmed that original “Teen Mom” star, adult film actress Farrah Abraham, would not return for Season 5. Her former co-stars, Maci Bookout, Catelynn Lowell and Amber Portwood, will be back. The next installment of "Teen Mom" is due to premiere on MTV in 2015.