Serum LH, FSH and testosterone response to the administration of a new LH-RH analog, D-Trp6-LH-RH, in normal men.

A long-acting superactive analog of LH-RH, D-Trp6-LH-RH was given to 23 normal men by several routes of administration (iv, im, sc, continuous infusion) and in increasing doses of 1 to 50 microgram. LH and FSH responses were obtained at doses as low as 2.5 microgram. The maximal absolute LH and FSH increment in response to a 10 microgram iv bolus injection of this analog was similar to 100 microgram of LH-RH. In addition, after administration of the analog the LH and FSH level was maintained at a higher than basal level for at least 8 hours. With a 50 microgram iv bolus injection, from 30 minutes onwards the increases in LH levels were significantly greater (P less than 0.05) than those elicited by the 10 microgram dose for at least 8 hours. Maximum release of LH and RSH was observed when this same dose was given as continuous infusion for 8 hours (P less than 0.05). There seemed to be no significant differences between the im and sc routes. Following the administration of the D-Trp6-LH-RH, testosterone levels were maintained above the normal values (P less than 0.02). The high potency and prolonged duration of action of this compound suggest its potential usefulness for increasing testosterone levels and for stimulation of spermatogenesis in men.