Megan,
My grandaughter takes DDAVP for kidney/bladder control. This hormone is regulated by the pitutary system.You can ask about it with your endocrinologist. Jennifer takes it thru the nasal tube. It basically helps control her sodium level to which your daughter may be having some issues that you just don't know of yet.( sodium level ) that is. The DDAVP controls her urine output.
Good luck,
George