Present study was performed to investigate whether TRH or metoclopramide (MCP) loading test was useful for the diagnosis of so-called occulted or latent hyperprolactinemia (transient increase of serum prolactin levels more than 30ng/ml during night; OHP).
The circadian profiles of serum prolactin levels were examined in 31 women (age : 23-32 years old) whose BBT charts showed biphasic patterns. Blood samplings had been done every two hours through an intravenous indwelling catheter without any disturbances. And seven cases of the OHP were selected. Five cases of the control were also selected at random. Then, LH-RH (100 μg) and TRH (500μg) loading test and LH-RH and MCP (10mg) loading test were performed to these cases in the mid-luteal phase of the same menstrual cycle at interval of two or three days, and serum FSH, LH and prolactin levels (at 0, 30, 60, 90,120 min. after the loading test) were determined by radioimmunoassay.
Serum prolactin levels in the OHP group showed significant higher levels than those of the control from 22 to 6 o'clock (p<0.05-0.005). By the administration of 500μg of TRH, serum prolactin levels of the OHP group increased significantly compared to those of the control at all sampling points (p<0.05-0.005), and also by the administration of 10 mg of MCP, the same result was obtained (p<0.05-0.02). The maximum peak of serum prolactin levels appeared at 30 min. after TRH or MCP loading. From these results, the diagnostic criteria for the OHP were decided tentatively as follows; serum prolactin levels more than 150 ng/ml at 30 min. after TRH loading or more than 250 ng/ml at 30 min. after MCP loading. Each value was approximated to the value of Mean - 1 S.D. in the OHP group which was obtained in this study. The usefulness of these criteria was examined in the patients with anovulatory cycles in the sterility clinic of our hospital and 24 cases of OHP by the TRH loading test (group A) and 19 cases of OHP by the MCP loading test (group B) were selected. Bromocriptine (5 mg/day) was administered for more than 30 days to these two groups and the effectiveness for the ovulation induction by the administration of bromocriptine was investigated for the confirmation whether the diagnostic criteria were appropriate.
The ovulations were induced in 18 cases of group A (75%) and 14 cases of group B (73.7%) by the administration of bromocriptine. There was no significant difference in the ratio of the ovulation induction between these two groups.
From these results, both TRH and MCP loading test were useful for the diagnosis of the OHP and the diagnostic criteria obtained in this study were appropriate for the diagnosis of the OHP.
