[Clinical significance of measurement of plasma melatonin concentration in women with irregular menstrual cycles].

To study the effects of melatonin on the human hypophyseal ovarian axis, we measured the concentrations of melatonin in the plasma of women with a regular menstrual cycle and of women with an abnormal menstrual cycle, at days 5 through 10 after the onset of menstruation or withdrawal bleeding. In seven women with a regular menstrual cycle, there was a tendency for the plasma melatonin concentration to gradually decrease chronologically from 49.0 +/- 9.8pg/ml (M +/- S.E.) at 9:30 h to 19.0 +/- 4.0pg/ml at 12:00 h. On the other hand, the plasma melatonin concentration at 21:30 h was 50.3 +/- 7.4pg/ml which was almost the same as the level at 9:30 h, while the concentration during the night significantly increased chronologically to 106.3 +/- 28.6pg/ml at 24:00 h. By comparing the plasma melatonin concentration measured during the day with that measured during the night, a significant difference was discovered after 21:40 h (p less than 0.05). The plasma melatonin concentration at 10:00 h and 22:00 h in 20 women with a regular menstrual cycle was 28.1 +/- 3.4pg/ml and 72.2 +/- 9.9pg/ml, respectively, showing a diurnal rhythm with a significantly higher level during the night than during the day. On the other hand, the plasma melatonin concentration in most of the women with an anovulatory cycle or amenorrhea was within the range of the mean level of +/- 1.5 x the standard deviation obtained from the 20 women with a regular menstrual cycle. However, an increase in plasma melatonin during the night was not found in three of nine women with an anovulatory cycle and one of two women with second grade amenorrhea.(ABSTRACT TRUNCATED AT 250 WORDS)