Expression of Two Glycoprotein Hormone Receptors in Larval, Parasitic Phase, and Adult Sea Lampreys.

•Expression of two lGpH receptors was determined in the three major lamprey life stages, larval, parasitic phase and adult.•lGpH-R I and II were co-expressed in larval endostyle and parasitic/adult thyroids.•lGpH-R I was expressed in larval ovaries; lGpH-R I and II were co-expressed in parasitic phase and adult ovaries.•lGnRH-I, -II, or -III increased plasma E2 concentrations.•lGnRH-III increased thyroid lGpH-R II expression with no significant change in plasma T4 concentrations in mature lampreys.