Launched in October 2010, the Hub has struggled to compete against Viacom's Nickelodeon empire and Walt Disney Co.'s Disney Channel and Disney XD. The network's ratings have grown, but its audience is tiny in comparison to its more entrenched rivals. Its most popular shows include "My Little Pony Friendship Is Magic" and "Littlest Pet Shop."
The departure of Loesch, a well-regarded programmer with lots of experience in the kids space, will likely set off speculation about the future strategy for the channel and the Discovery partnership with Hasbro.
The relationship between Hasbro and the Hub has been tense at times. Some former Hub executives have grumbled that Hasbro, which produces much of the content on the network, was more interested in a programming strategy that would help it sell toys versus attract viewers.
In some cases that meant shows that did well in the ratings but weren't moving product off the shelf were canceled, these people said. One such show was "G.I. Joe Renegades," which was pulled despite decent ratings. Another show, "Family Game Night," in which participants play life-sized versions of Hasbro games, had its episode order cut when board games became less important to Hasbro.
Asked about these concerns in an interview last year, Loesch said Hasbro does not "tell us how to run the business."
Advertising has also been an issue for the Hub. Because the network is half-owned by Hasbro, many rival toy manufacturers have avoided spending money on the network. Because of that, the Hub started adding more family fare and movies in the hopes of broadening its audience and being less reliant on just kids.
Hasbro has sunk several hundred million dollars into the Hub. Neither Discovery nor Hasbro discloses financial results for the network but Loesch said in the statement announcing her departure that the network is in "excellent financial health."
In a statement, Hasbro Chief Executive Brian Goldner praised Loesch's tenure, saying her "commitment to quality children's and family television entertainment is unparalleled."
Hasbro has given no public indication that it would like to exit the partnership. However, several months ago, Turner Broadcasting's Cartoon Network approached the Hub about a possible purchase of the channel, three people with direct knowledge of the situation said. Hasbro was said to be intrigued by the approach but Discovery was not interested, one of the people said.
A Hasbro spokesperson did not respond to a request for comment on the unsolicited Cartoon Network approach. Spokespeople for Discovery and Turner declined to comment.
No replacement has been named but there has been speculation on Tom Cosgrove, who currently heads Discovery's 3-D channel. Cosgrove has kids TV experience and worked with Loesch when she was running kids programming at Fox.
News of Loesch's departure was first reported by Deadline.
Follow Joe Flint on Twitter @JBFlint.