Acute effects of testosterone infusion and naloxone on luteinizing hormone secretion in normal men.

To evaluate the role of endogenous opioid pathways in the acute suppression of LH secretion by testosterone (T) infusion in men, we studied eight normal healthy volunteers who received a saline infusion, followed 1 week later by a T infusion (960 nmol/h) starting at 1000 h and lasting for 33 h. After 2 h of infusion (both saline and T), four iv boluses of saline were given hourly, and after 26 h of infusion, four hourly iv boluses of naloxone were given. Blood was obtained every 15 min for LH and every 30 min for T. T infusion increased the mean plasma T concentration 2.1-fold (18.7 +/- 2.1 to 39.5 +/- 3.5 nmol/L, saline vs. T infusion, P < 0.01). The mean plasma LH concentration was 7.9 +/- 0.5 IU/L during the saline control study and was decreased to 6.9 +/- 0.6 IU/L by the infusion of T (P < 0.05). LH pulse frequency was similar during both saline and T infusions (0.48 +/- 0.02 vs. 0.43 +/- 0.04 pulses/man.h, saline vs. T infusion). The mean LH pulse amplitude decreased from 4.3 +/- 0.4 IU/L during saline infusion to 3.3 +/- 0.2 IU/L during T infusion (P < 0.05). The administration of naloxone increased the mean plasma LH concentration significantly during saline infusion (7.6 +/- 0.4 to 10.0 +/- 0.9 IU/L, saline vs. naloxone boluses, P < 0.01), but not during T infusion (6.9 +/- 0.6 vs. 7.3 +/- 0.6 IU/L). LH pulse frequency increased significantly after the administration of naloxone during both saline and T infusions (0.54 +/- 0.04 to 0.71 +/- 0.08 pulses/man.h, saline vs. naloxone boluses during saline infusion, and 0.46 +/- 0.08 to 0.60 +/- 0.07 pulses/man.h during T infusion; P < 0.05). LH pulse amplitude was suppressed by T infusion, but administration of naloxone did not reverse this suppression. The mean amplitude of the LH response to exogenous GnRH (250 ng/kg) was decreased by T infusion from 48 +/- 13.5 to 31.2 +/- 8.5 IU/L (P < 0.01). Therefore, in men, the administration of naloxone increases LH pulse frequency during both saline and T infusions, but the acute suppression of LH pulse amplitude seen with T infusion was not reversed by naloxone. This pattern contrasts sharply with the effects of T infusion in pubertal boys, as elucidated by our earlier studies. The negative feedback effects of T on LH secretion are primarily hypothalamic in early pubertal boys and change to pituitary suppression in men.     

Acylated ghrelin inhibits spontaneous luteinizing hormone pulsatility and responsiveness to naloxone but not that to gonadotropin-releasing hormone in young men: evidence for a central inhibitory action of ghrelin on the gonadal axis

Context: Recent evidence suggests that ghrelin exerts a negative modulation on the gonadal axis. Ghrelin was reported to suppress LH secretion in both animal and human models. Moreover, acylated ghrelin (AG) also decreases the LH responsiveness to GnRH in vitro. Objective: The objective of the study was to evaluate the effects of AG infusion on spontaneous and stimulated gonadotropin secretion. Design, Participants, and Intervention: In seven young healthy male volunteers (age mean +/- sem 26.4 +/- 2.6 yr), we evaluated LH and FSH levels every 15 min during: 1) iv isotonic saline infusion; 2) iv saline followed by AG; LH and FSH response to GnRH (100 mug iv as a bolus), 3) alone and 4) during AG infusion; LH and FSH response to naloxone (0.1 mg/kg iv as a slow bolus), 5) alone and 6) during AG infusion. Results: Significant LH but not FSH pulses were recorded in all subjects under saline infusion. AG infusion inhibited LH levels [area under the curve((240-480)): 415.8 +/- 69.7 mIU/ml.min during AG vs. 744.6 +/- 120.0 mIU/ml.min during saline, P < 0.02] and abolished LH pulsatility. No change in FSH secretion was recorded. The LH and FSH responses to GnRH during saline were not affected by AG administration. However, AG inhibited the LH response to naloxone [area under the curve ((120-210)): 229.9 +/- 39.3 mIU/ml.min during AG vs. 401.1 +/- 44.6 mIU/ml.min during saline, P < 0.01]. FSH levels were not modified by naloxone alone or in combination with AG. Conclusions: AG inhibits both spontaneous LH pulsatility and the LH response to naloxone. Because AG does not affect the LH response to GnRH, these findings indicate that the ghrelin system mediates central inhibition of the gonadal axis.     

Naloxone increases the frequency of pulsatile luteinizing hormone secretion in women with hyperprolactinemia

The ability to change the frequency and amplitude of pulsatile GnRH secretion may be an important mechanism in maintaining regular ovulatory cycles. Hyperprolactinemia is associated with anovulation and slow frequency LH (GnRH) secretion in women. To assess whether the slow frequency of LH (GnRH) secretion is due to increased opioid activity, we examined the effect of naloxone infusions in eight amenorrheic hyperprolactinemic women (mean +/- SE, serum PRL, 160 +/- 59 micrograms/L). After a baseline period, either saline or naloxone was infused for 8 h on separate days, and LH was measured in blood obtained at 15-min intervals. Additional samples were obtained for plasma FSH, PRL, estradiol, and progesterone. Responses to exogenous GnRH were assessed at the end of the infusions. LH pulse frequency increased in all subjects from a mean of 4.0 +/- 0.5 pulses/10 h (mean +/- SE) during saline infusion to 8.0 +/- 1.0 pulses/10 h during naloxone infusion (P less than 0.01). LH pulse amplitude did not change, and mean plasma LH increased from 7.4 +/- 0.8 IU/L (+/- SE) to 11.2 +/- 1.5 IU/L during naloxone (P less than 0.01). A small but significant increase was seen in mean plasma FSH. Plasma PRL, estradiol, and progesterone were unchanged by naloxone infusion. These data suggest that elevated serum PRL reduces the frequency of LH (GnRH) secretion by increasing hypothalamic opioid activity and suggest that the anovulation in hyperprolactinemia is consequent upon persistent slow frequency LH (GnRH) secretion.     

Increased luteinizing hormone pulse frequency during sleep in early to midpubertal boys: effects of testosterone infusion

Gonadotropin secretion is pulsatile in prepubertal and early pubertal boys, and the onset of puberty is characterized by a sleep-associated rise in LH pulse amplitude. To determine whether an augmentation in LH pulse frequency as well as amplitude occurs at the onset of puberty, we studied gonadotropin secretion in 21 early to midpubertal boys. Blood samples were taken every 20 min (every 15 min in 4 boys) for LH determinations. A 2-fold increase in LH pulse frequency occurred during the nighttime sampling period (2200-0400 h) compared to that in the hours when the boys were awake (1000-2200 h). The maximum frequency (0.7 pulses/h) occurred between 2400 and 0200 h. The mean plasma LH concentration increased during the night from 2.3 +/- 0.2 (+/- SE) mIU/mL (2.3 +/- 0.2 IU/L) between 2000-2200 h to a maximum of 6.2 +/- 0.4 (6.2 +/- 0.4 IU/L) between 0200-0400 h. The mean plasma LH decreased to 5.5 +/- 0.4 mIU/mL (5.5 +/- 0.4 IU/L) between 0400-0600 h and to 4.2 +/- 0.5 (4.2 +/- 0.5 IU/L) between 0600-0800 h. Plasma testosterone rose during the night to a mean maximum value of 2.4 +/- 0.5 (+/- SE) ng/mL (8.3 +/- 1.7 nmol/L). This finding suggested that the rise in testosterone might play a role in decreasing LH secretion during the later hours of sleep (after 0400 h). To address this question and to study further the effects of testosterone in early puberty, we measured plasma LH concentrations every 10 min from 2000-0800 h in 8 early to mid-pubertal boys before and during short term testosterone administration. Saline or testosterone at a concentration of 9.33 micrograms/mL (32 mumol/L) was infused at a rate of 10 mL/h from 2100-1200 h to shift the nighttime testosterone rise 3 h earlier than would occur spontaneously. Blood samples were obtained every 10 min for LH and every 30 min for testosterone determinations from 2000-0800 h. Pituitary responsiveness was assessed by administering sequential doses of synthetic GnRH (25 and 250 ng/kg) at 1000 and 1200 h, respectively. The nighttime increase in LH pulse frequency and mean plasma LH concentration occurred between 2300 and 0200 h despite testosterone infusion. However, testosterone infusion was associated with significantly lower mean plasma LH concentrations from 0200-0800 h compared to those on the night of the saline infusion. Pituitary responsiveness to synthetic GnRH was unaltered by testosterone administration.(ABSTRACT TRUNCATED AT 400 WORDS)     

Naloxone does not reverse the suppressive effects of testosterone infusion on luteinizing hormone secretion in pubertal boys

In this study we wished to test whether, and if so when, the suppressive effects of testosterone on LH and, by inference, GnRH secretion are mediated via endogenous opioid pathways during male pubertal maturation. As a preliminary study, we evaluated the acute effects of a 24-h infusion of testosterone (T) in eight pubertal boys with constitutional delay of growth in order to determine the optimal time for administration of naloxone. Eight additional pubertal boys received a saline infusion, followed 1 week later by a similar T infusion starting at 1000 h and lasting for 33 h. After 2 h of infusion (both saline and T), four iv boluses of saline were given hourly, and after 26 h of infusion, four hourly iv boluses of naloxone were given. Blood was obtained every 15 min for LH and every 30 min for T measurements. T infusion increased the mean T concentration by 3.8-fold (P less than 0.001). Mean LH and LH pulse frequency were suppressed (P less than 0.01), and the sleep-associated increase in LH secretion was abolished. Naloxone administration during the infusion of T did not reverse the suppression of LH secretion. Compared to the saline control period, mean LH was significantly lower during T infusion during the time naloxone boluses were given (4.5 +/- 0.9 vs. 5.9 +/- 1.1 IU/L, T infusion and naloxone boluses vs. saline respectively, P less than 0.01). Although the suppression of LH pulse frequency remained significantly lower than that during the saline control period (0.23 +/- 0.04 pulses/boy.h during T infusion and saline boluses; 0.33 +/- 0.04 pulses/boy.h during T infusion plus naloxone boluses; 0.44 +/- 0.06 pulses/boy.h during saline infusion and saline boluses). Naloxone increased mean LH and LH pulse frequency only in the four older, more mature boys during the infusion of saline. Pituitary responsiveness to exogenous GnRH was not altered by infusion of T. We conclude that acute administration of T suppresses LH secretion and, by inference, GnRH secretion at all stages of pubertal maturation in boys. These negative feedback effects, however, cannot be reversed by coadministration of naloxone, even in mid- to late pubertal boys who respond to naloxone with increased pulsatile secretion of LH. These studies suggest that during pubertal maturation in boys, endogenous opioid pathways do not play a major role in the regulation of the negative feedback effects of T.     

Naloxone administration does not affect gonadotropin secretion in agonadal men either basally or during testosterone treatment

Naloxone administration has no effect on plasma gonadotropin levels of agonadal men. The present study was designed to evaluate whether testosterone replacement therapy could restore LH responsiveness to naloxone in such men. We measured plasma LH and FSH levels at 15-min intervals during naloxone infusion (8 mg in 1 min followed by 12 mg in 3 h) and for the following 3 h in a group of agonadal men both before and after at least 2 months of three different schedules of testosterone replacement therapy: 1) testosterone undecanoate, 40 mg three times a day by mouth; 2) testosterone enanthate 200 mg im every 2 weeks; and 3) testosterone enanthate 100 mg im once a week. Mean plasma gonadotropin levels as well as LH pulse frequency did not vary during naloxone infusion vs. placebo either basally or during each testosterone regimen. These results suggest that long term testosterone therapy does not affect the altered opioid modulation of gonadotropin secretion which is present in agonadal men.     

Central opioid activity in polycystic ovary syndrome with and without dopaminergic modulation

It has been hypothesized that brain opioid activity may be decreased in patients with the polycystic ovary syndrome (PCO) and that this decrease may, in part, explain the elevated levels of LH characteristic of the syndrome. We, therefore, examined the LH and PRL responses to naloxone infusions (2 mg/h for 4 h) in seven women with PCO and five weight- and estrogen-matched normal women. The infusions were given both before and after pretreatment with L-dopa-carbidopa (L-DOPA-C) because dopaminergic activity may be decreased in PCO, and dopamine may interact with the brain opioid system. Both PCO patients and normal women had similar responses of serum LH during naloxone treatment; the mean maximum LH responses were 53 +/- 15% (+/- SE) in normal women and 51 +/- 12% in PCO patients (P greater than 0.05). PRL levels were also unaffected by naloxone infusion. After L-DOPA-C pretreatment, baseline LH and PRL levels were unchanged in normal women and PCO patients, and the naloxone-induced LH rise was completely abolished in the normal women. However, in PCO patients, LH increased from 24.7 +/- 4 to 31 +/- 5 mIU/ml, with a mean maximum increase of 112 +/- 33% during naloxone infusion (P less than 0.05). We conclude that 1) brain or central opioid activity is not decreased in PCO; 2) increased central opioid activity does not appear to be responsible for the increased LH levels characteristic of the syndrome; and 3) decreased central dopamine activity and/or the interaction between the dopaminergic and opioid systems may be altered in PCO.     

The effect of naloxone on endogenous opioid regulation of pituitary gonadotropins and prolactin during the menstrual cycle

To determine the influence of ovarian sex steroid hormones on endogenous opioid regulation of pituitary FSH, LH, and PRL secretion, six women were studied during the follicular phase (days 8-9) and luteal phase (days 21-23) of their menstrual cycles. An iv bolus dose of 10 mg of the opiate antagonist naloxone was given, and plasma FSH, LH, and PRL were measured at -30, -15, 0, 15, 30, 45, 60, 90, 120, and 180 min. During the follicular phase, baseline plasma FSH and LH levels were 10.7 +/- 0.9 and 16.7 n+/- 2.0 mIU/ml (mean +/- SEM), respectively; the plasma PRL level was 11.7 +/- 1.2 ng/ml. Naloxone did not significantly alter plasma FSH, LH, or PRL during the follicular phase. Basal levels of LH were significantly lower during the luteal phase than during the follicular phase (P less than 0.01). During the luteal phase, plasma LH increased significantly from a basal level of 10.0 +/- 1.0 to 20.8 +/- 3.0 mIU at 30 min (P less than 0.001) and remained significantly elevated at 90 min. Similarly, plasma PRL increased significantly from a basal level of 11.0 +/- 0.7 to 16.2 +/- 2.7 ng/ml at 30 min (P less than 0.025), but decreased by 90 min to 12.5 +/- 1.5 ng/ml. Plasma FSH did not change after naloxone treatment. Our results suggest that endogenous opiates have a prominent inhibitory effect on pituitary gonadotropin and PRL secretion only during the luteal phase of the menstrual cycle.     

Role of endogenous opioid peptides in the initiation of the midcycle luteinizing hormone surge in normal cycling women

While compelling evidence indicates a pivotal role for endogenous opioids in the regulation of GnRH-LH pulsatile activity during the late follicular and luteal phases of the menstrual cycle, the participation, if any, of the opioidergic mechanism in the initiation of the midcycle surge has not been examined. Accordingly, we measured serum LH, FSH, estradiol (E2) and progesterone (P4) levels daily during 2 consecutive cycles in 12 normal cycling women. After a control cycle, each woman was infused with naloxone (30 micrograms/kg.h) for 24 h starting 3 days before the anticipated spontaneous midcycle surge. Blood samples were obtained at 15-min intervals for 8 h before, during, and 16 h after the naloxone infusion. Serum LH and FSH concentrations were measured in all samples, and serum E2 and P4 concentrations at 2-h intervals. Pulsatile LH secretion was analyzed using the cluster program. The opioidergic blockade elicited a robust increase in LH pulsatile activity and a 3-fold rise in serum FSH levels in 6 of the 12 women. This increased gonadotropin secretion lasted more than 24 h and was characterized by a progressive increase in LH pulse amplitude, which was 9-fold greater during the last 8 h of naloxone infusion [mean LH pulse amplitude, 36.5 +/- 4.5 (+/- SE) vs. 4.1 +/- 0.4 IU/L; P less than 0.001]. This increase was accompanied by a corresponding increase in transverse mean serum LH levels (83.3 +/- 13 vs. 20.7 +/- 3.2 IU/L; P less than 0.001), but no alteration of the interpulse interval (93 +/- 11 vs. 85 +/- 4 min). The peak serum LH concentrations exceeded 100 IU/L in all 6 of these women. This naloxone-advanced gonadotropin surge, resembling closely the spontaneous midcycle surge, resulted in a significantly shortened (P less than 0.001) follicular phase and a more than 2-fold elevation of serum P4, followed by assumed ovulation and normal luteal function. These 6 women had serum E2 levels immediately before naloxone infusion that were comparable to those during the preovulatory peak during the control cycle. In the 6 women who did not have a naloxone-induced increase in gonadotropin secretion the preinfusion serum E2 levels were substantially lower (P less than 0.001) than the values during the control cycle. These findings suggest that a transient decrease in opioidergic activity may contribute to the initiation of the midcycle gonadotropin surge in women.     

LUTEINIZING HORMONE AND FOLLICLE STIMULATING HORMONE SECRETION PATTERNS IN BOYS THROUGHOUT PUBERTY MEASURED USING HIGHLY SENSITIVE IMMUNORADIOMETRIC ASSAYS

Pulsatile gonadotrophin secretion patterns were studied in 32 normal boys (chronological age, CA 7.2-14.6 years) at different stages of pubertal development (5 in stage G1, 11 in G2, 5 in G3, 4 in G4, 7 in G5). Plasma LH and FSH concentrations were measured at 10 min intervals from 1200 to 1800 h and from 2400 to 0600 h using an immunoradiometric assay with a lower limit of detection of 0.15 IU/l for both LH and FSH. Plasma testosterone (T) was measured hourly. In the young prepubertal boys plasma LH was not detectable during day or night. In contrast, plasma FSH ranged from 0.7 to 1.4 IU/l. Plasma T was not detectable either (less than 0.25 nmol/l). In the older prepubertal boys a discrete pulsatile LH pattern (2 per 6 h) became discernible only during the night (range 0.1-0.4 IU/l). Plasma FSH also revealed a pulsatile pattern only during the night (2 per 6 h), while plasma T still remained undetectable. In the early pubertal boys (G2) a median daytime LH value of 0.37 IU/l was determined with 1 pulse per 6 h and at night definite LH pulses (4 per 6 h) were found in all boys (range 0.4-4.7 IU/l). Plasma FSH increased considerably to a median level of 2.50 IU/l during the day; most boys had a pulsatile FSH pattern (one per 6 h). Plasma T became detectable during the day (median 0.54 nmol/l) and night (median 1.16 nmol/l). With the progression of puberty the mean plasma level of LH and FSH, the LH/FSH pulse number and the LH/FSH pulse amplitude increased; plasma T rose as well, more obviously during the night. In G5, however, the LH pulse number decreased, while the LH level and pulse amplitude still increased, presumably as a result of the increased negative feedback action of sex steroids. Simultaneous LH/FSH pulses developed during the night at onset of puberty but during the day only towards the end of pubertal development. The use of these novel highly sensitive IRMA methods demonstrated nocturnal LH and both diurnal and nocturnal FSH pulsatility to be present in older prepubertal boys. The early detectable FSH level plus the existence of solitary FSH pulses throughout puberty as well as in adult men support the hypothesis of the existence of a GnRH-independent FSH secretion in men. Our results are in accordance with the following hypotheses: (1) puberty is brought about by GnRH secretion increasing with time, both in frequency and amplitude, and first appearing during the night.(ABSTRACT TRUNCATED AT 250 WORDS)     

ROLE OF ENDOGENOUS OPIOIDS IN REDUCING THE FREQUENCY OF PULSATILE LUTEINIZING HORMONE SECRETION INDUCED BY PROGESTERONE IN NORMAL WOMEN

It is well-established that the frequency of LH pulses varies during the normal menstrual cycle with a significant reduction in frequency in the luteal phase. Previous studies have indicated that both progesterone and opioids are able to reduce the frequency of LH pulses and in this study we sought to clarify the possible interaction between progesterone, endogenous opioids and GnRH neurons. Sixteen normal women in the mid-follicular phase (days 8-12) were randomly allocated to a control or treatment group and LH pulsatility assessed on one or two occasions by taking blood samples at 15 min intervals over 8 h. For the control women, LH pulsatility was assessed on one occasion during a saline infusion. The treated women received progesterone (50-100 mg/d for 7 d) at the end of which LH pulsatility was assessed before and after a naloxone infusion (2 mg/h for 8 h). Mean +/- SEM LH pulse frequency in the control women was 4.9 +/- 0.5 pulses/8 h which was significantly decreased to 3.0 +/- 0.3 pulses/8 h (P less than 0.01) in the progesterone treated women but not different from 5.5 +/- 0.3 pulses/8 h in those also treated with naloxone. Mean +/- SEM LH pulse amplitude in the control women was 2.3 +/- 0.3 IU/l, which was significantly increased to 4.8 +/- 0.7 IU/l (P less than 0.05) in the progesterone treated group, and to 3.7 +/- 0.4 IU/l (P less than 0.05) in the progesterone-treated women after naloxone. We conclude that progesterone slows the frequency of LH pulsatility by increasing endogenous opioid activity in the hypothalamus which may in turn inhibit the firing rate of the GnRH neurons.     

Aromatization mediates testosterone's short-term feedback restraint of 24-hour endogenously driven and acute exogenous gonadotropin-releasing hormone-stimulated luteinizing hormone and follicle-stimulating hormone secretion in young men

The present clinical study examines the neuroregulatory hypothesis that feedback restraint of LH and FSH secretion by testosterone requires in vivo aromatization. To test this postulate, we prospectively and randomly assigned 47 healthy young men to 1 of 5 parallel short-term (5-day) double-blind interventions with: 1) placebo; 2) high-dose ketoconazole (KTCZ, 400 mg orally 4 times daily) to block both Leydig-cell and adrenal steroidogenesis; 3) KTCZ and transdermal testosterone delivery (7.5 mg daily); 4) KTCZ and transdermal estradiol (0.05 mg daily); or 5) KTCZ, testosterone, and the selective and potent aromatase inhibitor, anastrazole (5 mg orally twice daily). Blood was sampled every 10 min for 27 h on the last day of intervention to quantitate 24-h mean spontaneous and 3-h post-GnRH-stimulated (100 ng/kg iv bolus) LH and FSH release. KTCZ administration lowered the serum total testosterone concentration markedly from (mean +/- SEM) 423 +/- 57 ng/dL (15 +/- 2.0 nmo/L) during placebo ingestion to 58 +/- 8.6 ng/dL (2.0 +/- 0.3 nmol/L) (P < 10(-3)). Transdermal androgen addback along with KTCZ blockade increased testosterone levels to 607 +/- 57 ng/dL (21 +/- 2.0 nmol/L). KTCZ exposure alone drove a 3-fold increase in serum LH concentrations (P < 10(-3)) and a 2.5-fold rise in FSH secretion (P = 0.015), as assessed by high-specificity immunoradiometric assays. Concomitant transdermal testosterone (or estradiol) delivery repressed the elevated secretion of both LH and FSH to mid-normal baseline values. A 3-fold administration of anastrazole, KTCZ, and testosterone completely opposed exogenous testosterone's suppression of 24-h LH and FSH secretion. Anastrazole coadministration likewise abolished testosterone-dependent inhibition of 3-h GnRH-stimulated LH and FSH release. In summary, assuming the specificity of anastrazole's inhibition of aromatase activity, we conclude that circulating testosterone in healthy men curtails endogenously driven as well as exogenous GnRH-stimulated LH and FSH secretion conditional on its in vivo aromatization.     

Operating characteristics of the male hypothalamo-pituitary-gonadal axis: pulsatile release of testosterone and follicle-stimulating hormone and their temporal coupling with luteinizing hormone

To appraise the physiological pattern(s) of episodic testosterone and FSH release in man, we withdrew blood samples at 10-min intervals for 24-36 h in a total of 15 normal men. We subjected the resulting FSH (15 men) and testosterone (5 men) time series to 3 statistically based and mathematically independent procedures for detecting hormone pulsatility, viz. Cluster analysis, the Detect program, and Fourier transformation. The Cluster technique disclosed discrete testosterone and FSH peaks occurring at mean (+/- SEM) interpulse intervals of 112 +/- 14 and 85 +/- 3.4 min, respectively. These values were not significantly different from the mean LH interpulse interval of 95 +/- 11 min. The average durations of the testosterone and FSH pulsations were 90 +/- 11 and 59 +/- 3 min, respectively. The mean testosterone pulse amplitude reached a maximal value of 910 +/- 92 ng/dL (31.5 +/- 3.2 nmol/L), which represented a mean increase of 242 +/- 26 ng/dL (8.4 +/- 0.9 nmol/L) above the preceding nadir. FSH pulses had a maximum of 7.2 +/- 0.3 IU/L, and an incremental amplitude of 1.3 +/- 0.1 IU/L. An independent pulse detection procedure. Detect, yielded a testosterone pulse frequency of 12.3 +/- 0.8 pulses/day [P = NS vs. Cluster program (13 +/- 1.9 pulses/day)]. The Cluster and Detect estimates of FSH pulse frequency were also similar, viz. 16 +/- 1.9 and 16 +/- 0.6 pulses/day. Further analysis by Fourier transformation revealed significant circadian periodicities for serum testosterone, FSH, and LH, which had mean nyctohemeral amplitudes of 185 ng/dL (6.4 nmol/L), 0.38 IU/L, and 1.3 IU/L, respectively. Cross-correlation analyses disclosed significantly positive uncorrected cross-correlations between LH and testosterone that were maximal at a testosterone lag of 60 min (range, 50-70 min). To eliminate high intrinsic autocorrelations within the testosterone and LH time series, stepwise autoregressive fitting was employed. The resulting partial cross-correlation matrices indicated that LH concentrations at any given instant were significantly positively correlated to testosterone concentrations lagged by 10 and 20 min. Similarly, contemporaneous LH and FSH concentrations were significantly positively correlated (r = 0.40-0.89; P less than 0.001). Moreover, autoregressive modeling disclosed significantly positive partial cross-correlations between LH and FSH at a FSH lag of 10 min. In summary, we have identified significant pulsatile as well as circadian (24-h) patterns of testosterone and FSH release in normal men.(ABSTRACT TRUNCATED AT 400 WORDS)     

QUANTITATIVE AND QUALITATIVE CHANGES IN LH SECRETION FOLLOWING PULSATILE GnRH THERAPY IN A MAN WITH IDIOPATHIC HYPOGONADOTROPHIC HYPOGONADISM

The pattern of bioactive and immunoreactive LH secretion before and during pulsatile GnRH therapy (18 micrograms/90 min) in a hypogonadotrophic hypogonadal male has been studied. Before treatment the patient was azoospermic and had low testosterone (1.2 nmol/l) with low and apulsatile immunoreactive LH (1.9 +/- 0.2 IU/l) and FSH (1.4 +/- 1.9 IU/l) levels. There was no detectable LH bioactivity. During the first 24 h of GnRH therapy there was a small increase in immunoreactive (5.4 +/- 0.8 IU/l) and bioactive (6.7 +/- 1.3 IU/l) LH, with an irregular pattern and little effect on testosterone production (2.2 nmol/l). Within 1 week of treatment both bioactive (30.5 +/- 6.8 IU/l) and immunoreactive (13.6 +/- 1.5 IU/l) LH levels were above the normal range and the pattern of secretion was pulsatile. The bioactive to immunoreactive (B:I) LH ratios within the pulses (2.6 +/- 0.3) were higher (P less than 0.01) than between pulses (1.97 +/- 0.1) and the testosterone concentration (17.8 +/- 2.1 nmol/l) was now normal. At one month LH secretion was similar and testosterone pulses of high amplitude were evident corresponding to high-amplitude bioactive LH pulses. By 3 months mature spermatozoa (1.3 x 10(6)/ml) were seen in the patient's semen. The pattern of LH secretion was pulsatile but the levels of bioactive (13.1 +/- 3.6 IU/l) and immunoreactive (9.5 +/- 1.3 IU/l) LH decreased towards the normal range reflecting maturation of the testicular feedback control at the pituitary level. This effect was more pronounced on bioactive rather than immunoreactive LH secretion (57% vs 32% relative decrease). At 6 months LH levels were similar and the sperm count was normal (34 x 10(6)/ml).     

Kisspeptin-54 stimulates the hypothalamic-pituitary gonadal axis in human males

CONTEXT: Mutation of the G protein-coupled receptor 54 is associated with a failure of reproductive function. The endogenous neuropeptide agonist for G protein-coupled receptor 54, kisspeptin, potently stimulates the hypothalamic-pituitary-gonadal axis in rodents and primates. OBJECTIVE: The present study was designed to determine the effects of elevating circulating kisspeptin levels on LH, FSH, and testosterone in male volunteers. DESIGN: This was a double-blind, placebo-controlled, crossover study. Setting: This was a hospital-based study. PARTICIPANTS: Male volunteers (n = 6) were recruited. INTERVENTIONS: Each volunteer received a 90-min i.v. infusion of kisspeptin-54 (4 pmol/kg x min) and a control infusion of saline (0.9%) in random order. MAIN OUTCOME MEASURE: Plasma LH, FSH, and testosterone concentrations were measured. RESULTS: Kisspeptin-54 infusion significantly increased plasma LH, FSH, and testosterone concentrations compared with saline infusion (mean 90-min LH: kisspeptin, 10.8 +/- 1.5 vs. saline, 4.2 +/- 0.5 U/liter, P < 0.001; mean 90-min FSH: kisspeptin, 3.9 +/- 0.7 vs. saline, 3.2 +/- 0.6 U/liter, P < 0.001; mean 180-min testosterone: kisspeptin, 24.9 +/- 1.7 vs. saline, 21.7 +/- 2.2 nmol/liter, P < 0.001). The plasma half-life of kisspeptin-54 was calculated to be 27.6 +/- 1.1 min. The mean metabolic clearance rate was 3.2 +/- 0.2 ml/kg x min, and the volume of distribution was 128.9 +/- 12.5 ml/kg. CONCLUSION: Elevation of plasma concentrations of kisspeptin in human males significantly increases circulating LH, FSH, and testosterone levels. Kisspeptin infusion provides a novel mechanism for hypothalamic-pituitary-gonadal axis manipulation in disorders of the reproductive system.     

Serum inhibin levels in normal men and men with testicular disorders

Serum concentrations of inhibin, FSH and LH were measured in 39 normal men and 127 men with testicular disorders resulting in infertility. The infertile men were divided into groups on the basis of their mean sperm count, FSH levels and karyotype. The mean (+/- S.D) serum concentrations of inhibin in the normal men was 554 +/- 156 U/l and did not differ significantly from those groups with oligospermia, azoospermia or Klinefelter's syndrome. Combined analyses of all groups did not reveal any significant correlation between serum concentrations of inhibin and FSH or with any other parameter measured. Serum concentrations of FSH and LH were positively correlated, and Leydig cell dysfunction, as evidenced by increased serum LH levels, low testosterone levels or a declining testosterone/LH ratio were found with severe spermatogenic damage. The failure of serum concentrations of inhibin to correlate with those of FSH levels or the degree of testicular damage raise questions as to the clinical value of this parameter alone.     

Endogenous opioid peptides modulate the effect of corticotropin-releasing factor on gonadotropin release in the primate

Stress can induce endocrine abnormalities and menstrual dysfunction in the primate. Here, we examine the effects that CRF, the principal neurohormone in control of the hypothalamic-pituitary-adrenal axis, exerts on pulsatile gonadotropin secretion and the role that the endogenous opioid peptides may play in this phenomenon. Ovariectomized rhesus monkeys were given a 5-h continuous iv infusion of physiological saline (2 ml/h), human CRF (100 micrograms/2 ml . h), or hCRF plus the opiate receptor antagonist naloxone (2 mg/2 ml/h; 5 mg in two experiments; n = 7 experiments/group). LH and FSH concentrations were measured at 15-min intervals for a 3-h preinfusion baseline control, during the 5-h infusion, and during a 2-h postinfusion observation period, while cortisol concentrations were measured at frequent intervals during the entire experiment. CRF infusion produced a progressive and significant decrease in both LH and FSH. Mean areas (+/- SE) under the LH and FSH curves during the 5-h CRF infusion, expressed as a percentage of preinfusion baseline, were 59.9 +/- 4.6% and 83.0 +/- 3.1% (+/- SE), respectively (P less than 0.001 and P less than 0.01 vs. saline controls). Large amplitude LH pulses were abolished during the CRF infusion. However, after cessation of CRF infusion, there was a rapid resumption of LH pulsatile release in four of the seven experiments. Addition of naloxone to CRF prevented the CRF-mediated suppression of LH and FSH release. Mean areas for LH and FSH during the 5-h combined infusion were 100.3 +/- 6.6% and 99.6 +/- 4.3% of the preinfusion baseline, respectively (P less than 0.001 and P less than 0.05 vs. CRH alone; NS vs. saline), and pulsatile LH secretion was maintained. Regardless of whether naloxone was administered, CRF increased cortisol levels significantly. Mean cortisol levels at the end of the CRF and CRF plus naloxone infusions were 48.2 +/- 10.4 and 52.9 +/- 7.4 micrograms/dl (+/- SE), respectively, compared to 21.0 +/- 3.0 with saline (P less than 0.05). These results demonstrate that in the ovariectomized rhesus monkey, CRF suppresses the secretion of both LH and FSH, and this effect can be sustained. They also indicate that the CRF inhibitory action on gonadotropin is primarily mediated by endogenous opioid peptides, independent of glucocorticoid levels.     

THE PITUITARY-LEYDIG CELL AXIS IN MEN WITH SEVERE DAMAGE TO THE GERMINAL EPITHELIUM

Eighteen men (mean age 27, range 18-30 years) treated for Hodgkin's disease with 6-8 courses of MVPP (Mustine, Vinblastine, Procarbazine and Prednisolone) have had Leydig cell function assessed by their steroidogenic responses to stimulation by a single bolus dose of HCG (1000 units intramuscularly). Normal age-matched men (n = 16) acted as controls. Baseline immunoreactive FSH was markedly raised in the patients (mean 18.1 +/- SD 6.9 vs 2.0 +/- 1.5 IU/l, P less than 0.0001) reflecting damage to the germinal epithelium. Immunoreactive LH was also greater in patients (10.3 +/- 3.9 IU/l) than in controls (3.9 +/- 1.9 IU/l, P less than 0.0001). There were no differences between the baseline testosterone, androstenedione, oestradiol, oestrone and sex hormone binding globulin (SHBG) concentrations. The testosterone/SHBG ratios were similar in the two groups and there was no correlation between baseline LH and testosterone concentrations or testosterone/SHBG ratios. Testosterone, androstenedione, oestradiol and oestrone secretion in response to HCG stimulation were similar at 24 h and 96 h in both groups. In order to explain the paradox of elevated immunoreactive LH in the face of normal testicular steroidogenesis in such patients, LH biological activity (B) as well as LH immunoreactivity (I) and FSH and testosterone were estimated in a second similar group of patients (n = 17, mean age 27, range 17-43 years) and in a further age-matched control group (n = 17). Bioactive and immunoreactive LH levels were significantly increased (P less than 0.005 and P less than 0.001, respectively) in the patient group.(ABSTRACT TRUNCATED AT 250 WORDS)     

CHANGES IN THE QUALITATIVE AND QUANTITATIVE SECRETION OF LUTEINIZING HORMONE (LH) FOLLOWING ORCHIDECTOMY IN MAN

The effect of orchidectomy and thus withdrawal of testicular hormones on the biological and immunological properties of plasma LH was studied. Plasma samples were obtained from five men (mean age 71, range 65-81 years) with advanced carcinoma of the prostate, before orchidectomy and 1, 4, 8 and 16 weeks after surgery. LH bioactivity was estimated by a mouse Leydig cell bioassay and immunoreactivity by radioimmunoassay, using the same human pituitary LH standard 68/40. FSH and testosterone were measured by radioimmunoassay. Similar baseline data were obtained from a group (n = 17) of normal adult men (26, 19-36 years). Baseline bioactive (40 IU/l, median) and immunoreactive (10.8 IU/l) LH levels in the patients were higher (P less than 0.01) than in the controls (15.1 and 5.7 IU/l respectively), but bioactive to immunoreactive (B:I) LH ratios (3.4 +/- 0.2 versus 2.8 +/- 0.7) and testosterone levels (15.3 vs 18.7 nmol/l) were no different, consistent with compensated Leydig cell failure in the elderly men. After orchidectomy there was a greater increase in immunoreactive (46.6 IU/l at 16 weeks) than bioactive (80.3 IU/l) LH levels i.e. a fourfold vs twofold increase from baseline values. Consequently the B:I LH ratio decreased significantly (1.8 +/- 0.4 at 16 weeks) from the baseline ratio (P less than 0.0001) and that of the controls (P less than 0.01). These data indicate that acute withdrawal of testicular sex steroids results not only in quantitative change in LH secretion but also in qualitative change that decreases the biopotency of the LH molecules.     

Stimulation of ovarian follicular maturation with pure follicle-stimulating hormone in women with gonadotropin deficiency

According to the 2-cell theory, ovarian steroidogenesis requires the coordinate action of both FSH and LH. To evaluate the relative importance of these hormones in follicular maturation, a randomized cross-over study was performed in 10 women with complete gonadotropin deficiency (absence of pulsatile LH secretion and no LH response to LHRH). Five women were treated with highly purified FSH (LH bioactivity, 0.09%) and 3 months later with human menopausal gonadotropin (hMG; LH bioactivity, 65%), each given for 10 days at a daily dose of 225 IU FSH, im. The sequence was reversed in the other 5 women. hCG (5000 IU) was administered im 24 h after the last injection of FSH or hMG. Plasma estradiol (E2), estrone (E1), androstenedione (A), testosterone, LH, and FSH concentrations and urinary LH and FSH were measured daily by RIA. Ultrasonography was performed during each treatment and 2 days after each hCG injection. After FSH treatment, mean plasma and urinary FSH levels increased, mean plasma LH did not change, and urinary LH increased slightly but not significantly from 91 +/- 32 (SE) to 164 +/- 55 mIU/24 h (10(-3) IU/24 h). After hMG treatment, mean plasma and urinary LH and FSH levels increased accordingly. The mean basal plasma E2 [11 +/- 1 pg/mL (40 +/- 4 pmol/L)] and E1 [14 +/- 4 pg/mL (52 +/- 15 pmol/L)] levels increased after FSH treatment to 207 +/- 69 pg/mL (760 +/- 253 pmol/L) and 82 +/- 21 pg/mL (303 +/- 78 pmol/L), respectively (P less than 0.01), but plasma A did not change. In response to hMG, the mean plasma E2, E1, A, and testosterone levels increased more than during FSH treatment. Ultrasonography revealed multiple preovulatory follicles (greater than or equal to 16 mm) in 2 women after hMG and 1 woman after FSH treatment; therefore, hCG was not administered. In 3 women given FSH, hCG did not induce ovulation. hCG induced ovulation in 8 women given hMG and in 6 women given FSH, based on ultrasonography and plasma progesterone levels. Thus, in the presence of profound gonadotropin deficiency pharmacological doses of FSH, with minute LH contamination, are capable of stimulating ovarian follicular maturation, underlining the key role of FSH in folliculogenesis.