Abstract
The circadian and pulsatile secretions of prolactin were studied in 15 pregnant and 5 puerperal women. Blood samples were taken every 15 minutes for 3 hours during daytime and at night. Diurnal levels of prolactin and estradiol were examined in 135 pregnant women. In addition, prolactin and estradiol of 8 parturient women were measured every 15 minutes until 24 hours after delivery. Prolactin and estradiol levels increased gradually in advance of pregnancy, and a positive correlation was revealed between prolactin(Y) and gestational weeks(X): Y = 7.125X-42.997, r = 0.9955. Furthermore, a positive correlation between prolactin(Y) and estradiol(X) levels was observed: Y = 4.439X + 44.115, r = 0.7590. The circadian secretion of prolactin was observed in 15 out of 20 cases studied. The pulsatile secretion of prolactin was revealed in all 20 cases. The daytime pulse-frequency significantly decreased in the 2nd trimester and that of the nighttime also decreased in the 3rd trimester. The pulse-amplitude increased in advance of pregnancy, but amplitude/baseline value ratio was stationary 28% during the daytime and 34% during the nighttime in every trimester of pregnancy. 63.0% of coincidence in prolactin pulse with increase of immunoreactive LH-hCG was observed. The pulsatile secretion of hCG has not been yet reported. However, the pulsatile increase of immunoreactive LH-hCG was observed in 10 pregnancies, while LH was not detected in any pregnancy by highly specific LH assay. This suggested that immunoreactive hCG changed in a pulsatile manner in the blood of pregnant subjects. A highly significant decline of prolactin levels was observed from 10 hours before until 4 hours after delivery, which did not correlate with changes of estradiol levels. These results indicated that the pulsatility and circadian secretion of prolactin were preserved during pregnancy and puerperium and also suggested that prolactin secretion during pregnancy, delivery and puerperium was regulated by at least 3 factors: estradiol, dopamine and LH-hCG.
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