Twenty-four hour prolactin (PRL) secretory patterns during pregnancy

To determine if the central nervous system "program" controlling PRL secretion is operative during pregnancy, three pregnant women (12th, 20th and 32nd week of gestation) had 24-hour, 20-minute interval plasma sampling and polygraphic monitoring of nocturnal sleep. All three subjects showed episodic PRL secretion during waking which became augmented during nocturnal sleep. Since the number of "major" PRL secretory episodes was similar to normals, the increased PRL levels were most probably achieved by increased secretion per secretory episode. These findings suggest that during pregnancy, the PRL sleep related secretory "program" is maintained in a qualitative manner, albeit at a higher set-point.