title: Circadian periodicity of serum prolactin concentration in man.
abstract: Immunoreactive human serum prolactin of pituitary origin has been measured by a radioimmunoassay developed for ovine prolactin. Blood samples were collected at four-hour intervals during a 24-hour period from 12 non-pregnant women, three pregnant women, and seven adult men. A circadian periodicity was found in serum prolactin concentration, with peak values during the night, between 1 a.m. and 5 a.m. for the non-pregnant women, and at 5 a.m. for the adult men. Mean serum levels of prolactin were 1.5 times higher in non-pregnant women than in men. In women investigated during the last month of their pregnancy the mean serum prolactin levels were 2.3 times higher than in the non-pregnant women, but there was no circadian periodicity.
mesh_terms: D000328:Adult; D002940:Circadian Rhythm; D005260:Female; D006801:Humans; D007456:Iodine Isotopes; D008297:Male; D008875:Middle Aged; D011247:Pregnancy; D011388:Prolactin / Q000097:blood*; D011863:Radioimmunoassay; D012737:Sex Factors
chemical_list: D007456:Iodine Isotopes; D011388:Prolactin