Forty-three patients with secondary hypothalamic amenorrhea and 17 healthy women in the early and late folliculin phases of the normal cycle were tested with 100 micrograms synthetic LH-RH i. m. The LH and FSH concentration in the plasma was measured before and after the injection of synthetic LH-RH. The patients were divided into two groups, according to the degree of estrogen deficit. The basal concentration and maximum LH increase in the group of hypothalamic amenorrhea with a milder estrogen deficit proved to be significantly higher than in the group with a higher estrogen deficit (22.2 +/- 7.2 versus 12.7 +/- 9,3 p less than 0.01 and, respectively, 74.8 +/- 17.00 versus 34.4 +/- 11.2, p less than 0.01). In healthy women with the normal cycle, the basal LH and FSH concentrations and the maximum increase after the LH-RH application were significantly higher in the late than in the early folliculin phase. The basal LH and FSH concentrations and their increase after the LH-RH injection appear to depend on the concentration of endogenous estrogens, both in normal cycle and in secondary hypothalamic amenorrhea.