Prolactin can have an indirect action on body composition through other hormones that regulate glucose and fat metabolism. In particular the hormone adiponectin. Adiponectin stimulates glucose utilization and fatty-acid oxidation, mainly in visceral fat. Elevated levels of prolactin will decrease adiponectins function, which is seen in those with insulin resistance and hypertriglyceridemia. In contrast, healthy, in range prolactin levels upregulate adiponectin function.
I think I recall there's a relationship of sodium retention and prolactin levels? To what degree, I'm not sure.
Prolactin is involved with many biological actions such as immunological and dermatological.