ABSTRACT
Gonadotrophins and prolactin are protein hormones of the anterior pituitary. Human prolactin is of another physicochemical character than gonadotrophins; it is a single polypeptide chain of some 200 amino acids without carbohydrate attachment. Its primary structure is very different from that of human growth hormone but exhibits some 80% homology with ovine prolactin. Prolactin acts on ectodermal or integumentary structures in all classes of vertebrates: mammary gland, broad patch of birds, epidermal sloughing in reptiles, skin changes associated with water drive in amphibians, and mucus production in teleosts. Bioassay methods have been proposed for the measurement of prolactin but none of them are entirely satisfactory. All in vivo methods are insufficiently sensitive and thus none of them are applicable to plasma without preliminary extraction. Most of the bioassay methods for prolactin require an extraction of prolactin from urine or serum in order to be able to measure the concentration of the hormone in these body fluids.
