Serum prolactin levels at different stages of menstrual cycle and during a 24-hour period in Malay women

Radioimmunoassay technique has been used to investigate the variation in the serum human prolactin (hPRL) levels at different stages of menstrual cycle and during a 24-hours period in Malay women. The results showed that the serum hPRL concentrations during menstrual (24.5 ± 4.3 ng/ml), preovulatory (36.6 ± 7.4 ng/ml), ovulatory (29 ± 5.3 ng/ml) and postovulatory (26.6 ± 5.2 ng/ml) periods were not significantly different among each other. The hPRL level was highest during night-sleeping, at 0200hr and was significantly different from the values obtained at 1400, 2000, 0800 and 1400 (last sampling) hours (P < 0.01).