[Circadian changes in serum prolactin in a group of apparently healthy subjects].

Serum immunoreactive prolactin was evaluated in 16 female and 5 male apparently healthy subjects aged 21-76 yr. After a period of synchronisation, with sleep from 22 to 5 and standardized meals at 8-8.30, 12-12.30, 17.30-18, venous blood samples were taken at 4, 8, 12, 16, 20 and 24. The radioimmunological data were processed using an ordinary chronogram technique and quantified by mean cosinor method. A significant (p less than 0.05) circadian rhythm was noted, with an acrophase at 1.45, amplitude of 2.17 and Mesor 6.89. Chronobiological studies are thus needed to determine the best normal temporal values of prolactin when setting control standards in pathological situations.