Twenty-Four Hour Pattern of Luteinizing Hormone Secretion in Normal Men with Sleep Stage Recording

Abstract

Plasma luteinizing hormone (LH) was measured by radioimmunoassay at 20-min intervals around the clock for 24 hr in 5 normal adult men. During the nocturnal S-hr sleep period, polygraphic monitoring of sleep stages was carried out. All 5 subjects showed episodic secretion of LH characterized by rapid rises and the declining slopes approximated the half-life of LH. Calculation of LH “half-life” from the declining phase of the LH secretory episodes gave variable estimates within subjects and between subjects (65–114 min). The longer T1/2 estimates calculated by this method, contrasted with previous studies where LH half-life was determined directly by the measurement of LH disappearance, is probably the result of small amounts of LH being secreted during the declining phase of the LH secretory episode. This study failed to show a 24-hr LH rhythm or relationship of LH secretory activity to the sleep-wake cycle. The marked temporal variability of the LH system throughout the 24-hr period clearly demonstrates the limitations of the isolated daily LH determination. The finding that the initiation and cessation of LH secretory episodes occurred within narrow, well-defined ranges may be considered evidence in favor of some degree of negative feedback control. Comparison between the LH and cortisol secretory patterns was made in an attempt to characterize differences in endocrine control mechanisms.