Patterns of spontaneous LH release in normo- and hyperprolactinaemic women

Hyperprolactinaemia may be associated with functional amenorrhoea. In order to evaluate the possible role of abnormal spontaneous LH secretion in hyperprolactinaemic amenorrhoeic women, plasma LH was measured at 15 min intervals for 300 min in 12 normal women during the early follicular phase of the menstrual cycle and compared to that observed in 11 hyperprolactinaemic amenorrhoeic subjects. Mean plasma prolactin was 9.1 +/- 3.6 ng/ml (X +/- SEM) in the euprolactinaemic and 168 +/- 32 ng/ml in the hyperprolactinaemic group. Sex steroids including oestrone, oestradiol, progesterone and 17-hydroxyprogesterone were similar in the 2 groups. Mean plasma LH levels over the 300 min sampling period were 9.4 +/- 1.6 mIU/ml in the normal subjects and 7.5 +/- 1.0 mIU/ml in the hyperprolactinaemic patients (P greater than 0.10). Every normal woman exhibited at least one LH spike in excess of 10 mIU/ml. Five hyperprolactinaemic patients failed to exhibit any LH spikes above 10 mIU/ml (P less than 0.02 compared to controls). Thus, hyperprolactinaemia was associated with an absence of LH spike activity in 45% of patients studied and this abnormality may play an aetiologic role in the hypogonadism observed in these subjects; in those hyperprolactinaemic subjects with pulsatile LH secretion, however, other explanations for their amenorrhoea should be considered.