Luteinizing hormone secretory pattern before and after removal of Leydig cell tumor of the testis

We studied the luteinizing hormone (LH) secretory pattern in three patients, aged 30, 23 and 43 years, with gynecomastia due to Leydig cell tumor of the testis, before and 6 months after unilateral orchidectomy. The results were compared to those of 11 normal fertile controls aged 20-35 years. Blood sampling was done at 20-min intervals from 22.00 h to 10.00 h. The LH data were analyzed with the Cluster analysis algorithm with "optimal parameters for LH male data" to determine the pulse interval and pulse amplitude. The Expfit program was applied to LH pulses to calculate the apparent half-life of immunoreactive LH. Before surgery, when compared to controls, the patients had a low to normal testosterone/estradiol ratio (0.053, 0.110, 0.046 vs 0.148 +/- 0.038) and mean LH levels (1.96, 3.7, 2.55 vs 4.0 +/- 1.9 IU/l), decreased pulse amplitude (2.65, 3.01, 2.21 vs 3.31 +/- 1.41 IU/l) and reduced apparent half-life of LH (74, 69, 78 vs 97 +/- 16 min). After removal of the Leydig cell tumor, the testosterone/estradiol ratio returned to the normal range (0.141, 0.177, 0.093) while an increase in mean LH levels (5.75, 7.90, 4.88 IU/l), LH pulse amplitude (3.07, 6.05, 2.86 IU/l) and apparent half-life of LH (138, 106, 104 min) was observed in all three patients. Our data indicate that endogenous hyperestrogenism in patients with Leydig cell tumor of the testis results in an inhibition of LH secretion, and suggests that such inhibition could result from a reduction in pulse amplitude and apparent half-life.