The luteinizing hormone pulsatile secretion: Diurnal excursions in normally cycling and postmenopausal women

Abstract

While numerous investigations have determined characteristics of episodic luteinizing hormone (LH) secretion in women, any diurnal LH rhythmicities during eugonadal and hypogonadal states have not been accurately addressed. Accordingly, blood was sampled at 15-min intervals for 24 h in 45 normally cycling women (16 early follicular (EFP), 14 late follicular (LFP), 15 mid-luteal phase (MLP) women) and in eight postmenopausal women (PMW). Pulse attributes (amplitudes, interpulse intervals) determined in the LH secretory profiles were fitted to cosinor functions to assess diurnal variabilities. In both eugonadal women and PMW, significant (p less than 0.05 or less) diurnal excursions were observed in mean LH levels, with maximal acrophase amplitudes occurring in the EFP and MLP. While these 24-h swings peaked at comparable times (11.00-17.00) during the menstrual cycles, a significant (p less than 0.001) shift in acrophase times to early morning hours (05.30) was noted for PMW. Significant (p less than 0.05 or less) 24-h periodicities were also found for the LH pulse amplitudes. LH pulses were of greater magnitudes during night hours in both cycling women and PMW. A slowing of LH pulses (p less than 0.05 or less) was noted during sleep in EFP and, distinctly, in MLP women. These observations demonstrate diurnal variations in LH secretion and its pulsatile attributes in eugonadal women. Differences in time course and magnitude of these diurnal excursions may be explained by variations in the sex steroid environments. In turn, steroids may modulate other neuroendocrine determinants regulating central time-keepers.

Differential and Gonad Stage-Dependent Roles of Kisspeptin1 and Kisspeptin2 in Reproduction in the Modern Teleosts, Morone Species1

“…During the course of the experiment, we observe a gradual increase in plasma Lh levels also in the control group. This phenomenon may be explained by diurnal rhythms of Lh as reported in mammals [59,60] and fish [61,62] or may be due to acute stress imposed by the handling and treatments [63]. Kiss1-15 also up-regulates gnrh1 and gpr54-2 mRNA levels in prepubertal fish, although higher levels than Kiss2-12 are needed to obtain the same effect (Fig.…”

Progesterone acutely increases LH pulse amplitude but does not acutely influence nocturnal LH pulse frequency slowing during the late follicular phase in women

“…Moreover, some methods of assessing LH pulse changes may have masked true differences. For instance, although one study described significant diurnal changes of LH pulse frequency in 11 of 14 women in the late follicular phase, cosinor analysis of composite data revealed no significant changes (28).…”

“…Although several studies by Loucks and colleagues (15)(16)(17) suggest that late follicular LH pulse frequency slows by 20 -30% during sleep, others have not found nocturnal decreases in LH frequency during the late follicular phase (6,28,29,35). The reasons for discrepancies among these studies are unclear, but possibilities include the use of different LH assays, unfavorable LH sampling frequencies [e.g., every 15 (28,29) or 20 (35) min vs. every 10 min (15-17)], and older methods of pulse detection [e.g., Santen and Bardin method (6,35)]. Methods for assigning LH pulse frequency differed as well, although employed methods were not always clearly reported.…”

“…In addition to the above, some (6,28,36) but not all (35) studies have suggested diurnal slowing of LH pulse frequency during the luteal phase. Taken together, these and our findings suggest that diurnal slowing of LH pulse frequency may occur throughout the menstrual cycle in adult women, with changes being most prominent in the early follicular phase.…”

Circadian Rhythms during Aging

“…However, a 24-hour variation in LH secretion has been reported in postmenopausal women in several studies, with maximal levels observed during the nighttime hours [34]. In contrast, another group reported no consistent 24-hour variation after menopause [35].…”