Testicular Steroid Response to Continuous and Pulsatile Intravenous Luteinizing Hormone-Releasing Hormone Administration in Normal Men

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Abstract
In 18 healthy normal men Leydig cell response was examined following intravenous luteinizing hormone-releasing hormone (LH-RH) administration under standardized conditions. The same total amount of LH-RH was administered for 3 hours both in a continuous (1 .mu.g/min; C (1,1)) and in a pulsatile fashion, by giving a 20 .mu.g dose at 20 minute intervals, P (20,20), and a 60 .mu.g dose at 60 minute intervals, P (60,60). Following the different modes of LH-RH administration which all caused 3-4 fold elevations of the mean endogenous luteinizing hormone (LH) concentrations and 1.7-2 fold elevations of the mean follicle-stimulating hormone (FSH) serum levels, an overt increase of the mean testosterone (T) levels was noticed up to 1.5 x the baseline value. No difference was observed in the total amount of T release among the investigated groups. The patterns of the T response, however, clearly differed from one another with a rapid increase, during the C (1,1) and the P (20,20) LH-RH administration, and a delayed but persistent T increase in the P (60,60) experiment. The mean 17-hydroxyprogesterone (17-OHP) concentrations demonstrated a similar course to T in the P (60,60) experiment, while significant increases of the oestradiol (E 2) levels were never observed in all three experiments. In view of the comparable LH and FSH increments in response to LH-RH administration in either experiment the differences in T responses may be explained by assuming a direct effect of LH-RH on Leydig cell steroidogenesis in the men.

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