AJP - Endocrinology and Metabolism, Vol 256, Issue 4 E510-E515, Copyright © 1989 by American Physiological Society
Interpulse interval of GnRH stimulation independently modulates LH secretion
L. S. O'Dea, J. S. Finkelstein, D. A. Schoenfeld, J. P. Butler and W. F. Crowley Jr
Reproductive Endocrine Unit, and Massachusetts General Hospital, Boston.
To examine the importance of the interpulse interval of
gonadotropin-releasing hormone (GnRH) stimulation in modulating gonadotroph
responsiveness, a fixed individualized dose of GnRH was administered to
eight GnRH-deficient men at intervals selected randomly from the
distribution of luteinizing hormone (LH) interpulse intervals of normal
men. The responses were compared with data derived from a study of LH
pulses in 20 normal men. A positive relationship was found between LH pulse
amplitude and the preceding interpulse interval both in the GnRH-deficient
(P less than 0.05) and in the normal (P less than 0.003) men. The
distributions of LH pulse amplitudes appeared to differ between the two
groups with failure of the study paradigm to reproduce the distribution of
low-amplitude pulses of the normal men in the GnRH-deficient men. There was
significantly more variability about the line that related interpulse
interval and LH amplitude in the normal men (P less than 0.004) in whom the
amount of GnRH could vary physiologically. This difference remained
significant both for pulses with amplitudes below (P less than 0.01) or
above (P less than 0.03) the mean of the normal men. These studies
demonstrate that the GnRH interpulse interval is an independent determinant
of pituitary responsiveness and that alterations in the amount of GnRH
secreted from the hypothalamus are an important determinant of LH pulse
amplitude in men.
