An evaluation of the diagnostic value of synthetic luteinizing hormone releasing hormone.

The potential use of LH-RH as a test of pituitary function in women has been investigated. In this study the synthetic material was administered intravenously, and samples of peripheral blood were removed at defined times. The levels of plasma oestradiol, LH and FSH were determined by radioimmunoassay. The administration of incremental doses of LH-RH (from 1.56 to 450 mug) demonstrated that a maximal response was obtained with 100 mug in the majority of apparently healthy subjects. Accordingly, this amount was selected as the standard dose for use in a test of pituitary function. The application of this test to 96 patients with secondary amenorrhea showed that the release of LH and FSH (as assessed by the maximum value, and the area under the response curve) was within the normal range in 82, high in 4 and low in 10. There was no correlation between the cause of the amenorrhea, the results of the LH-RH test, and the endogenous levels of oestradiol, LH and FSH. In addition 5 patients with primary amenorrhea and 8 patients with pituitary disorders were tested with LH-RH. In primary amenorrhea low basal levels of LH were found, but all subjects had a normal response to LH-RH. In 3 patients with clinical hypopituitarism the basal levels of gonadotrophins were in the normal range, but there was an impaired response to LH-RH. It is concluded that 100 mug of LH-RH administered intravenously may be used to test the ability of the pituitary to release LH and FSH, but the magnitude and duration of the response is not of additional diagnostic value.