Re: abnormal serum prolactin
Mine was also abnormal (slightly low like yours). Gyn thought it was related to hypothyroid and would resolve with thyroid treatment. (She might be referring me to an endocrinologist, though, too.)
A lot of times when things are borderline low or high, doctors just ignore them. Having had a LOT of bloodwork over the last few months, it's amazing how much my levels of all sorts of things swing around. So often an isolated, slightly abnormal reading is just overlooked.
If you're concerned, though, have them repeat the test in a few months. If it's still low, then you could look into it.