According to Yelich-O'Connor, Pearl had been sick for most of his life but a specialist had identified the issue and "everything was looking good" as she administered new medications.
She has credited her dog with helping her write her next album, saying "he was instrumental to the discovery that was taking place. I felt he led me towards the ideas."
And with his passing, she has shared that it will take time for her to recalibrate, "now that there's no shepherd ahead of me, to see what the work is going to be."
She concludes her letter by asking fans for patience, writing, "I have lost my boy, and need some time to see the good again."
Lorde has previously released three albums: her debut, Pure Heroine, in 2013, followed by the EP, Love Club, and Melodrama in 2017.