Pharmacokinetics of intravenous luteinizing hormone-releasing hormone administration in men: effects of various dosages

Abstract

Exogenous luteinizing hormone-releasing hormone (LH-RH) was intravenously administered as a single-bolus injection to 26 healthy normal men. LH-RH doses were selected at 1, 2.5, 5, and 20 micrograms for exploration of the optimum LH-RH dose to obtain adequate pituitary stimulation. Blood samples (for LH-RH and LH determinations) were collected at frequent intervals from 10 minutes before to 60 or 90 minutes after injection. LH-RH peak levels varied, in a dose-dependent way, between 119 +/- 16 and 517 +/- 70 ng/l. Peak values were all reached between 1 and 3 minutes after injection, and elimination occurred rapidly, with half-lives between 2.6 +/- 0.4 and 5.2 +/- 1.0 minutes. The area under the curves increased significantly (P less than 0.01) if the doses of LH-RH had been augmented from 1 to 20 micrograms. Maximum LH values were reached more rapidly in the low-dose (1 and 2.5 micrograms) experiments (between 13.5 and 16.3 minutes), with an obvious decline afterwards. The area under the LH curves increased (P less than 0.01) if the doses of LH-RH had been elevated from 1 to 2.5 micrograms, but no further increase of LH release occurred (P greater than or equal to 0.21) if LH-RH doses were further elevated from 2.5 to 20 micrograms. The current study demonstrates that a 2.5-micrograms intravenous LH-RH dose is best suited for an adequate pituitary stimulation in normal men.