Lena Dunham wanted her fans to know what had happened to her dog Lamby.

Ms. Dunham, the writer, producer and actor best known for the HBO series “Girls,” adopted Lamby in January 2013. But the cream-colored mutt stopped making appearances in Ms. Dunham’s social media feeds, replaced, it seemed, by two fresh-faced poodles, Susan and Karen.

So on June 21, Ms. Dunham disclosed on Instagram that Lamby had “suffered terrible abuse as a pup” and that, because of the resulting behavioral problems, she handed him over to a facility in Los Angeles.