Hourly integrated concentrations (IC) of growth hormone (GH), prolactin (PRL) and cortisol were determined by a continuous sampling procedure in six obese women, before and at the end of a 12 day fast, and in eight normal controls under basal conditions. Hormonal 24 h IC and nyctohemeral variations were calculated from these data. Nyctohemeral rhythms were investigated by the periodogram method.

A significant increase over basal values of 24 h IC of PRL, GH and cortisol was observed at the end of the fasting period. Nyctohemeral variations-but not nyctohemeral rhythm-of IC-GH were found in normal subjects. They were abolished in obese patients under basal conditions but restored during fasting. The circadian rhythm of cortisol was not altered in obesity. A shift of the normal nyctohemeral rhythm of PRL was observed in obese patients, but the normal pattern was restored during fasting.