A novel type of prolactin expressed in the bullfrog pituitary specifically during the larval period.

•PRL1B cDNA was cloned from the larval bullfrog pituitary.•PRL1B mRNA levels decline at metamorphic climax.•The adult pituitary neither expresses PRL1B mRNA nor immunoreactive PRL1B.•Immunoreactive PRL1A and PRL1B exist in the larval pituitary.•This is the first report on the presence of PRL1B in the amphibian pituitary.