FSH Pulses Research Articles

The pulsatile secretion of bioactive luteinising hormone in normal adult men

We have studied bioactive and immunoreactive LH pulsatility in 11 normal men. The temporal relationship of plasma LH, testosterone, and FSH were also investigated. Blood samples were taken at 10-minute intervals for 6 h and bioactive LH levels were determined using an in vitro mouse Leydig cell bioassay. Testosterone, LH and FSH were determined by standard radioimmunoassay. Twenty-two bioactive LH pulses were detected (amplitude 8.5 +/- 4.9 IU/l, mean +/- SD) with a frequency of 2 +/- 0.8/6 h compared with only 18 immunoreactive LH pulses (amplitude of 3.6 +/- 1.8 IU/l) and a frequency of 1.6 +/- 0.5/6 h. Bioactive:immunoreactive LH ratios increased (p less than 0.01) from the preceding pulse nadirs (2.26, range 1.66-4.28) to the pulse peaks (2.71, range 1.99-4.67). Twenty FSH pulses (seen in all but one subject) of low amplitude (0.7 +/- 0.6, median 0.5 IU/l) were also present. There was a close temporal relationship between testosterone and FSH secretion with bioactive and immunoreactive LH pulses with lags of 30-60 and 0 min, respectively. We conclude that immunoreactive LH pulses are discordant from bioactive LH pulses in 18% of occasions. Further, the mean amplitude of bioactive episodes were approximately 2.6 times greater than that of immunoreactive episodes, whereas interpulse period and pulse duration were similar. The increase in bioactive:immunoreactive ratio at pulse peaks may indicate that in normal men LH pulses are enriched with a more biopotent form of the molecule.

Postmenopausal androgen secreting ovarian tumour: pathophysiological implications; a case report

Hyperandrogenism in women is usually accompanied by a disruption of the hypothalamic-pituitary-ovarian axis; however, the precise effect of chronically elevated androgens on this axis is poorly understood. We report a postmenopausal woman with a virilizing ovarian tumour in whom the effects of chronic testosterone secretion on the hypothalamic-pituitary axis was investigated. A 56-year-old woman was evaluated for hirsutism and hyperandrogenism of recent onset. Peripheral serum testosterone was high (19.4 nmol/l), while gonadotropins were below normal for a postmenopausal woman, FSH (19.7 IU/l) being higher than LH (10.3 IU/l). Four LH and 1 FSH pulse were detected over 4 h. A left intraovarian testosterone secreting tumour, shown by catheterization of the ovarian veins and containing imperfect crystalloids of Reinke, was excised. Postoperatively, peripheral testosterone became undetectable, while gonadotropins rose to normal postmenopausal values. This patient's LH FSH ratio was less than 1, in contrast with other situations of chronic hyperandrogenism. This could be explained by the concomitant hypoestrogenic state, and/or the theoretical absence of inhibin. The interest of this case resides in that it constitutes an appropriate model for studying the effects of testosterone on LH and FSH secretion in the absence of the other two classically involved modulators, namely oestrogens and inhibin.

Pulsatile Secretion of LH and FSH in Prepubertal and Early Pubertal Boys Revealed by Ultrasensitive Time-Resolved Immunofluorometric Assays

Pulsatile secretion of LH and FSH was examined in 10 prepubertal (aged 4.5-12.9 y) and seven early pubertal (aged 12.8-14.5 y) boys with ultrasensitive (0.019 and 0.014 IU/L) time-resolved immunofluorometric assays. Plasma LH and FSH levels were measured every 15 or 20 min for 6 h during the day and night. The lowest mean LH level in a prepubertal boy was 0.02 IU/L and in eight other prepubertal boys mean LH levels were less than 0.4 IU/L. In early pubertal boys the mean LH levels ranged from 0.3 to 6.5 IU/L. The difference in mean FSH level between prepubertal (0.61 IU/L) and early pubertal boys (1.85 IU/L) was smaller than the difference in LH level. All boys had significant LH and FSH pulses. The LH interpulse interval was 135 +/- 86 min (mean +/- SD) and 76 +/- 65 min for the prepubertal and pubertal boys, respectively (p less than 0.01). For FSH, the respective values were 150 +/- 122 and 221 +/- 157 min (p = NS). The mean LH pulse amplitudes were 11-fold greater in the early pubertal boys than in the prepubertal boys, whereas the mean FSH pulse amplitudes were similar between the two groups. The present method shows that the mean LH levels in prepubertal boys are much lower, and the increase during puberty larger, than previously reported. The increase is apparently due to increased pulse frequency and amplitude. The increase in mean FSH level is smaller and evidently not caused by an increase in pulse frequency or pulse amplitude.

Patterns of Pulsatile Pituitary Glycoprotein Secretion in Central Hypothyroidism and Hypogonadism*

Five patients with central hypothyroidism and hypogonadism due to mass or infiltrative lesions of the pituitary and hypothalamus were studied to determine pulsatile pituitary glycoprotein secretion patterns. Blood samples were obtained every 15 min over 24 h, and TSH, LH and FSH were measured by immunoradiometric assays. Hormone pulses were located by cluster analysis, and pulse patterns were compared to those in normal subjects. Three patients had unmeasurable LH levels, while two had a normal number of low amplitude pulses. In contrast, all patients had normal FSH pulse frequency, and only one had low pulse amplitude. Three patients had normal 24-h TSH pulse frequency and amplitude, while two had slightly decreased pulse parameters. However, all failed to show normal nocturnal increases in TSH pulse amplitude. Thus, anatomical hypothalamic-pituitary lesions disrupt pulsatile glycoprotein secretion in a discordant fashion. LH is most severely affected, with abnormal pulse patterns similar to those in idiopathic central hypogonadism. FSH and TSH pulses are relatively preserved, but loss of the usual nocturnal increase in TSH pulse amplitude is sufficient to cause clinical hypothyroidism. Whether these defects reflect intrinsic pituitary disease or impaired hypothalamic releasing factor function remains to be determined.

Gonadal Control of Pulsatile Secretion of Luteinizing Hormone and Follicle-Stimulating Hormone in Prepubertal Boys Evaluated by Ultrasensitive Time-Resolved Immunofluorometric Assays

To elucidate the role of the testis in the control of LH and FSH secretion before puberty, we examined pulsatile LH and FSH secretion in six prepubertal boys with primary testicular failure (two boys with masculine pseudohermaphroditism, two boys with the Klinefelter's syndrome, and two boys with anorchia) and eight normal prepubertal boys. Plasma LH and FSH levels were measured every 15 min for 6 h during the day and night with ultrasensitive (0.019 and 0.014 IU/L) time-resolved immunofluorometric assays. In all six hypogonadal boys the mean FSH level was above the range of the normal prepubertal boys, whereas the LH level was elevated in only one boy. All boys had LH and FSH pulses. The FSH pulse interval in the anorchid boys was shorter than that in the normal boys, but this was not observed in the other hypogonadal boys. The LH pulse interval in the anorchid and other hypogonadal boys was the same as that in the normal boys. The FSH pulse amplitudes were higher in the anorchid and other hypogonadal boys than in the normal boys, but the LH pulse amplitudes were higher only in the anorchid boys. We conclude that in prepuberty the testes have little effect on LH secretion, but that they are involved in the regulation of FSH levels. In primary testicular failure, the elevation of FSH levels is associated with an increase in FSH pulse amplitude and, in the absence of testicular steroids, possibly also with an increase in FSH pulse frequency.

Pulsatile Secretion of Ovarian Steroids in the Mid-luteal Phase of the Menstrual Cycle

The possibility of the pulsatile secretion of pituitary gonadotropins (LH and FSH) and ovarian steroids (estradiol and progesterone) was studied. In addition, an evaluation was made of the regulatory factors for steroid secretion of corpus luteum in view of the response behavior of the secretion of LH, FSH, estradiol and progesterone when loaded with hCG and gonadotropin releasing hormone (Gn-RH). The study was performed on 9 cases of infertile women in the mid-luteal phase of a normal menstrual cycle. In 5 cases, blood was collected every 30 minutes and over 24 hours. Thereafter, 2,500 iu of hCG was given twice to another subject at 8 hour intervals, and blood was collected every 30 minutes from immediately after the 1st administration over 16 hours. In the other 3 cases, 15 micrograms of Gn-RH was given at an interval of 90 minutes, and blood was collected every 20 minutes for 16-24 hours. Then, the frequency and amplitude of each pulse for LH, FSH, estradiol and progesterone were calculated under the modified Santen's rule in situ and when loaded with Gn-RH, and the relationship between pulses of gonadotropins and those of estradiol and progesterone was analysed by determining the number of concomitant pulses. The hormone dynamics when loaded with hCG were also assessed. The pulse frequency and amplitude in situ of each hormone were 10.6 +/- 0.8 times/24 h and 4.9 +/- 0.6 miu/ml for LH, 9.9 +/- 9.9 times/24h and 1.3 +/- 0.1 miu/ml for FSH, 9.2 +/- 0.9 times/24h and 34.3 +/- 2.7 pg/ml for estradiol, 7.4 +/- 0.5 times/24 and 3.7 +/- 0.4 ng/ml for progesterone. The coincidence of estradiol pulses and LH pulses was 37 times, and the concomitant ratio of LH pulse to estradiol pulse was 81%. The coincidence of progesterone pulses and LH pulses was 31 times, and the concomitant ratio of LH pulse to progesterone pulse was 84%. Furthermore, the concomitant ratio of FSH pulse to estradiol pulse or progesterone pulse was 61% or 70%, respectively. The mean plasma concentration of LH, estradiol and progesterone during 8 hours after the 1st administration and 2nd administration of hCG changed from 29.9 +/- 2.3 to 41.8 +/- 1.6 miu/ml, from 140.3 +/- 3.0 to 160.6 +/- 3.6 pg/ml and from 19.2 +/- 1.0 to 25.7 +/- 0.6 ng/ml, respectively. These values increased significantly after the second injection (P less than 0.001).(ABSTRACT TRUNCATED AT 400 WORDS)

Determination of the Normal Range of Serum LH and FSH Levels in Normal Adult Males

To determine the normal range of serum LH and FSH levels, blood samples from 53 normal adult males were measured by a double antibody radioimmunoassay system and a new immunoradiometric assay (IRMA) system. It was necessary to evaluate the individual pulsatile secretion and the differences in measured values among laboratories to determine the normal range. Therefore, in 53 normal adult males lacking any evidence of hormonal abnormalities, blood was sampled at 9:00 a.m. daily for 3 days, and these samples were measured in 3 laboratories. The result of the hormone concentration of blood sample was not appropriate as the normal range because of the high amplitude of LH and FSH pulses. Coefficient values (CV) between the mean value of the first two samples and the mean value of all three samples were small. Therefore, the mean value of the first two samples was clinically accurate for use as the normal range. Significant differences in measured values were observed among the 3 laboratories. The normal range, which included individual pulsatile secretion, and the differences in measured values among the laboratories was as followings: LH (RIA): 7.6-13.7 mIU/ml, LH (IRMA): 2.1-4.7 mIU/ml, FSH (RIA): 4.7-9.5 mIU/ml, FSH (IRMA): 3.0-7.4 mIU/ml. The serum LH and FSH levels of 68 untreated male infertility patients tended to rate high with respect to our normal range. It was considered that the normal range determined in this study was useful for clinical management.

Bioactive Follicle-Stimulating Hormone Release in Nutritionally Growth-Retarded Ovariectomized Lambs: Regulation by Nutritional Repletion*

The nutritionally growth-retarded ovariectomized lamb provides a model system to investigate the regulation of immunoreactive and bioactive FSH release in the absence of feedback effects of ovarian products. We examined the acute effects of nutritional repletion on FSH release in this model. Five March-born lambs were weaned at 7 weeks of age and placed on a limited diet. All were ovariectomized at 31 weeks. At 37 weeks, they were fed ad libitum for 14 days. Blood samples were collected at 12 min intervals for 4 h on day -1 (restricted) and days 2, 7, and 14 of ad libitum feeding, and serum FSH concentrations were measured by both RIA and a Sertoli cell aromatase in vitro bioassay. Mean concentrations of serum immunoreactive FSH (I-FSH) and the bioactive FSH (B-FSH) increased 2- and 3-fold, respectively, after ad libitum feeding for 14 days. Pulse analyses by two objective computerized programs, DETECT and CLUSTER, revealed the presence of FSH pulses (predominantly B-FSH) during the restricted phase, as well as ad libitum fed phases, at times where I-LH pulses were not detected. In contrast to the increases in I-LH pulse frequency during ad libitum fed states, FSH pulse frequency remained stable whereas pulse amplitude increased. In addition, the overall B-FSH pulse amplitudes were 57 +/- 7% (mean +/- SE of three different pulse analyses) greater than I-FSH pulse amplitudes, implying preferential enrichment of FSH bioactivity. The results suggest that the mechanisms governing both the quantitative and qualitative changes in circulating FSH concentrations are extremely sensitive to changes in level of nutrition. The asynchronous occurrence of FSH pulses in the absence of I-LH pulses suggests that FSH may be more sensitive to small changes in GnRH secretion than I-LH, or that a hypothalamic releasing factor specific for FSH may be released.

Changes in pulsatile secretion patterns of LH, FSH, progesterone, androstenedione and oestradiol in cows after superovulation with PMSG

Six heifers were injected i.m. with 2500 i.u. PMSG followed by 15 mg prostaglandin 48 h later. Serial blood samples were collected through a catheter in the caudal vena cava every 10 min for 8 h on Day 10 (7 h after PMSG administration), during luteal regression (7 h after prostaglandin administration) and on the day thereafter. Four normally cyclic heifers served as a control group. Concentrations of progesterone, androstenedione, oestradiol, LH, FSH, and PMSG in the vena cava samples were measured and the frequency and amplitudes of episodic pulses of all hormones were estimated except for PMSG. Ovaries were collected by ovariectomy at 50 h after onset of luteal regression to determine the number of preovulatory follicles (non-atretic follicles greater than or equal to 10 mm). Stimulation of follicular growth by administration of PMSG resulted in the following effects on the secretion of steroids and endogenous gonadotrophins. (1) There were no alterations in progesterone concentration and the amplitude and frequency of episodic pulses. Mean (+/- s.e.m.) concentrations were 54.1 +/- 5.8, 19.1 +/- 3.1 and 3.4 +/- 0.9 nmol/l on Day 10 (L), during luteal regression (LR) and on the day thereafter (F) respectively. (2) There were no alterations in the episodic secretion patterns of androstenedione. Mean concentrations were 0.20 +/- 0.02, 0.15 +/- 0.02 and 0.11 +/- 0.02 nmol/l for the L, LR and F periods respectively. (3) There was an increase in oestradiol concentration from 17.1 +/- 3.0 pmol/l during the L period to 233.7 +/- 86.4 pmol/l during the F period. Pulse amplitude was enhanced compared to corresponding periods in control animals whereas pulse frequency remained the same. The oestradiol concentration was significantly correlated with the number of preovulatory follicles (r = 0.82, P less than 0.05). (4) There was a suppression of the frequency of episodic LH pulses (/8 h) during the LR (3.2 +/- 0.7) and F (4.3 +/- 0.4) periods compared to corresponding periods in control heifers (9.5 +/- 0.9 and 7.0 +/- 1.5 respectively). The preovulatory LH peak occurred earlier in 4 of 6 treated heifers. (5) There was a suppression of FSH concentrations, pulse amplitude and frequency during the LR and F (17.4 +/- 0.9 mg/l, 4.7 +/- 0.8 microgram/l and 7.5 +/- 0.4 pulses/8 h) periods compared to the corresponding F-period values (35.6 +/- 6.2 mg/l, 9.8 +/- 1.6 micrograms/l and 9.3 +/- 0.3 pulses/8 h) in control heifers.(ABSTRACT TRUNCATED AT 400 WORDS)

Specific, Time-Dependent Actions of Low-Dose Ethinyl Estradiol Administration on the Episodic Release of Growth Hormone, Follicle-Stimulating Hormone, and Luteinizing Hormone in Prepubertal Girls with Turner's Syndrome *

To investigate the actions of acute and chronic low doses of ethinyl estradiol (EE) on the pulsatile characteristics of GH and gonadotropin release we studied seven girls with Turner's syndrome [mean age, 7.5 +/- 0.75 (+/- SE) yr] on 3 separate study days. At baseline (study I), blood was drawn every 20 min from 2000-0800 h for GH, LH, and FSH determinations. One month after study I the patients were started on 100 ng/kg EE, orally, daily, and an identical study was repeated 1 week (study II) and 5 weeks (study III) from the initiation of low dose EE therapy. A pulse detection algorithm, Cluster, was used to objectively analyze pulsatility profiles. There were consistent and significant increases in all seven patients after 5 weeks of low dose EE therapy in mean GH concentrations (study I, 7.0 +/- 1.1 micrograms/L; study III, 13.4 +/- 1.7; P = 0.008), mean area under the GH pulse (study I, 602 +/- 52 micrograms/L.min; study III, 1350 +/- 261; P = 0.026), and mean GH pulse amplitude (study I, 14.0 +/- 2.2 micrograms/L; study III, 32.8 +/- 6.0; P = 0.018); with no detectable changes in GH pulse frequency (study I, 5.3 +/- 0.6 pulses/12 h; study III, 5.3 +/- 0.4). These findings were not accompanied by any significant changes in plasma somatomedin-C or serum estradiol concentrations or urinary cytological maturation indexes. Conversely, the amount of radioimmunoassayable FSH activity was suppressed after low dose EE therapy, with a decrease in mean FSH concentrations (study I, 23.5 +/- 6.6 IU/L; study III, 5.9 +/- 1.2; P = 0.035) and mean pulse amplitude (study I, 28.6 +/- 8.6 IU/L; study III, 8.2 +/- 1.8; P = 0.038), with no detectable changes in FSH pulse frequency (study I, 7.6 +/- 0.6 pulses/12 h; study III, 7.3 +/- 0.6). Similar qualitative changes in LH pulsatility were observed after low dose estradiol administration. In conclusion, our results demonstrate that low dose EE therapy results in a significant augmentation of pulsatile GH activity, with reciprocal decreases in gonadotropin concentrations in girls with Turner's syndrome. Such observations indicate an exquisite sensitivity of gonadotrope and somatotrope function to low dose estrogen action in this prepubertal hypogonadal model.

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)

LHRH pulse frequency in normal and infertile men

The aim of this study was to examine the hypothesis that decreased LHRH pulse frequency may be responsible for the preferential rise in FSH in infertile men. The LH pulse pattern was determined as an index of hypothalamic LHRH secretion in 21 infertile patients with idiopathic azoospermia or oligoasthenozoospermia and 14 fertile age-matched controls by frequent blood sampling at 10-min intervals for 24 h. The infertile patients were further divided into three groups according to their relative concentrations of FSH and LH: (1) normal FSH and LH, (2) raised FSH but normal LH, and (3) raised FSH and LH. LH pulses were detected by a computerized algorithm (Munro) validated against a threshold method. Concentrations of FSH, testosterone, sex hormone-binding globulin and oestradiol were measured in pooled plasma. Luteinizing hormone pulse frequencies in normal men were not significantly different from the infertile group as a whole. Similarly, mean LH pulse frequencies in infertile subgroups 1, 2 and 3 were not significantly lower than normal. Pulse interval, however, was increased in subgroup 1 compared with normal. Mean 24 h LH in group 2 was significantly higher than normal, but still within the normal range. The total testosterone, but not the free testosterone index was significantly decreased in the infertile group compared with normal. There was no correlation between mean FSH and LH pulse frequency or interval. In conclusion, our results show that in patients with seminiferous tubular dysfunction, the typical pattern of raised plasma FSH, increased LH pulse amplitude, raised FSH: LH ratio and normal or marginally low testosterone was not associated with any significant deviations in LHRH pulse frequency from the range observed in normal fertile men. This is not compatible with the hypothesis that decreased LHRH pulse frequency is associated with or the cause of the preferential rise in FSH in men with idiopathic infertility. Thus unlike anovulatory infertility in females, functional defects of hypothalamic LHRH secretion remain an uncommon finding in male infertility. Attempts to treat idiopathic oligozoospermia by altering LHRH pulse frequency is therefore unlikely to yield any clinical benefit.

Endogenous Inhibin Suppresses Only Basal Follicle- Stimulating Hormone Secretion but Suppresses All Parameters of Pulsatile Luteinizing Hormone Secretion in the Diestrous Female Rat

The purpose of these studies was to ascertain which parameters of pulsatile gonadotropin secretion are regulated by endogenous inhibin in the intact diestrous female rat. This was determined by examining the changes in the secretion parameters of FSH and LH that resulted from immunoneutralizing endogenous inhibin in diestrous I female rats. Passive immunoneutralization of endogenous inhibin was achieved using specific, high titer ovine antiserum generated against the alpha-subunit of the recently described inhibin molecule. The optimal times after inhibin immunoneutralization to observe the changes in FSH secretion were determined in initial experiments. Pulsatile secretion of both FSH and LH was observable in the diestrous female. Two hours after inhibin immunoneutralization, the mean trough level, mean peak level, and overall mean level of FSH began to increase. The maximal increase and plateau of these parameters were observed 5 h after antiserum injection. During the period of increase, mean FSH pulse amplitude was also increased, but returned to the level observed in control (normal sheep serum-injected) animals when the parameters of trough, peak, and overall mean FSH reached their plateau levels. FSH pulse frequency was not changed at any time. These results indicate that endogenous inhibin affects only the basal parameters of FSH secretion without affecting pulsatile FSH secretion. The transient increase in FSH pulse amplitude resulted from FSH pulses being superimposed on the increasing basal FSH secretion. In contrast, immunoneutralization of endogenous inhibin rapidly increased all parameters (i.e. pulse amplitude and frequency, mean trough and peak levels, and mean plasma levels) of LH secretion. In addition, pituitary sensitivity to an exogenous LHRH challenge was increased in inhibin-immunoneutralized females in terms of stimulated LH secretion. As a result of the already increased rate of basal secretion, the actual quantity of FSH released in response to the LHRH challenge was greatly increased in the inhibin-immunoneutralized rats compared with the normal sheep serum-injected controls; however, the increase in the rate of FSH secretion stimulated by the LHRH challenge was the same in both groups. The observations from these studies collectively demonstrate that inhibin acts endogenously to suppress those parameters of gonadotropin secretion that are regulated by LHRH.

Secretory patterns of LH and FSH and follicular growth following administration of PGF 2α during the early luteal phase in cattle

Two studies were conducted to determine the changes in gonadotropin secretion associated with growth and development of the largest follicle and the ability of the largest ovarian follicle present on Day 5 following estrus to ovulate if luteal regression is induced. In both studies, cows received either saline (i.m.) or prostaglandin F 2α (PGF 2α; 25 mg i.m.) on the fifth day post estrus. Frequency of LH pulses declined (P<0.01) with increasing day of cycle, while pulse amplitude and duration increased (P<0.05) in saline-treated cows. In PGF 2α-treated cows, LH remained as high frequency-low amplitude pulses. Secretory patterns of FSH were similar between the two groups. In Experiment 2, the largest ovarian follicle present was marked around its periphery with sub-epithelial injections of charcoal. In saline-treated cows, the size of the charcoal marked follicles generally decreased, indicating atresia. A corpus luteum was present within the area of a previously marked follicle in three PGF 2α-treated cows. The size of the marked follicles either decreased or increased in the remaining PGF 2α-treated cows, with ovulation occurring at a different site. In summary, PGF 2α-induced luteal regression on the fifth day of estrus subsequently alters the frequency, amplitude and duration of LH pulses, but not FSH pulses, and the largest follicle present on Day 5 either increases or decreases in size or ovulates when PGF 2α is given on Day 5 following estrus.

Effects of gonadal steroids on gonadotropin secretion in males: studies with perifused rat pituitary cells.

The feedback effects of testosterone (T) and estradiol (E2) on FSH and LH secretion were compared in dispersed pituitary cells from adult male rats perifused with pulses of GnRH. Cells were stimulated with 10 nM GnRH for 2 min every 1 h. T (10 nM) pretreatment for 24 h reduced the amplitude of FSH and LH pulses to 77 +/- 4% (mean +/- SE) and 47 +/- 3% of control values, respectively (P less than 0.01), whereas 6-h T treatment was without effect. By contrast, interpulse secretion of FSH was increased after 24 h T to 184 +/- 7% of the control value (P less than 0.01), but interpulse LH release was unchanged (104 +/- 5%). E2 (0.075 nM) treatment of pituitary cells reduced GnRH-stimulated FSH and LH release within 2 h to 75 +/- 2% and 73 +/- 3% of control values, respectively (P less than 0.01). E2 pretreatment for 24 h stimulated (P less than 0.025) GnRH-induced FSH (136 +/- 10%) and LH (145 +/- 8%) release and also increased (P less than 0.01) interpulse FSH (127 +/- 5%) and LH (145 +/- 8%) secretion. These data indicate that the suppression of FSH and LH secretion by T in males is due in part to a direct effect on the pituitary. The findings that T suppresses GnRH-stimulated FSH less than LH, and that T stimulates interpulse FSH, but not LH, provide evidence for differential regulation of FSH and LH secretion by T. The dissimilar actions of T on GnRH-stimulated pulses and interpulse gonadotropin secretion suggest that interpulse secretion is unrelated to stimulation by GnRH, although its physiological significance is unknown. Since E2, in physiological levels for males, increased pituitary FSH and LH secretion, the suppression of gonadotropin secretion by E2 in vivo in males may result from an effect on the hypothalamic pulse generator; however, additional studies are needed before extending these conclusions to higher mammals and men.

Transferrin Secretion in Response to Different Modes of FSH Stimulation and Cycloheximide in Superfused Sertoli Cell Cultures

The influence of different modes of FSH stimulation and cycloheximide on transferrin secretion by rat Sertoli cells was investigated using a superfusion culture system. Sertoli cells from 18-day-old rats were cultured in serum-free medium on Matrigel-covered slides first in static conditions for 19 hours, and then superfused at a flow rate of 2.5 ml/hour. After an equilibration period of 48 hours to establish the basal rate of transferrin secretion, the cultures were exposed to various modes of FSH stimulation. Sertoli cells stimulated intermittently (20 min/2 hours) up to 22 hours responded to each consecutive FSH pulse with a rapid increase of transferrin secretion followed by a decline toward basal values. Continuous 22-hour exposure to FSH elicited an immediate increase followed by irregular fluctuations and a transient decline towards the baseline. With either mode of FSH stimulation, there was a secondary prolonged increase in transferrin secretion. Although cultures stimulated intermittently or continuously during the entire experimental period (22 hours) secreted similar cumulative amounts of transferrin (10.8 +/- 0.5 micrograms and 11.1 +/- 0.8 micrograms, respectively), there was a direct correlation between the secreted amount of transferrin and the duration of FSH exposure up to 8 hours. Addition of cycloheximide decreased both basal and FSH-stimulated transferrin secretion. However, even when cycloheximide was added 1 hour before FSH, an early secretory peak in response to FSH was still observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of administration of an alpha 2-adrenergic agonist, xylazine, on pulsatile gonadotrophin secretion in anoestrous horse mares.

Two experiments were performed to test the hypothesis that the seasonal suppression of gonadotrophin pulse frequency in anoestrous horse mares reflects inhibitory neural mechanisms. In a preliminary experiment (Exp. 1) conducted in February, 4 anoestrous mares were sedated by repeated intravenous injections of xylazine, an alpha 2-adrenergic receptor agonist. On the day of treatment, 1-2 LH pulses were observed in xylazine-treated mares. In contrast, during a 12-h period only 1/8 untreated control mares exhibited a LH pulse. In Exp. 2, the effect of xylazine-induced sedation on pulsatile gonadotrophin release was examined in 4 anoestrous mares on two occasions before (18 November and 9 December) and after (23 December and 6 January) an abrupt, artificial increase in day length. Treatment with xylazine was associated with an overall increased FSH (P less than 0.01) and LH (P less than 0.05) pulse frequency, compared with that observed during 12-h pretreatment periods. To evaluate an effect of treatment at the various time during the experimental period, the change in FSH pulse frequency was analysed, since occasionally FSH pulses were unaccompanied by a change in serum LH values indicative of a LH pulse. On two occasions before increased daylength only 1/4 and 3/4 mares exhibited an increase in FSH pulses; in contrast, 14 days after increased daylength (23 December), 4/4 mares exhibited increased FSH pulse frequency associated with treatment. After 27 days of increased daylength (6 January), endogenous FSH pulse frequency was greater than before increased daylength and treatment with xylazine was unaccompanied by a further increase.(ABSTRACT TRUNCATED AT 250 WORDS)

139 PREMATURE THELARCHE VARIANT: A NEW SYNDROME OF PRECOCIOUS SEXUAL MATURATION

Studies of gonadotrophin pulsatility and pelvic ultrasound morphology distinguish between isolated premature thelarche (IPT) and central precocious puberty (CPP) (Eur J Pediatr 1986; 145:190) We have observed 6 girls (age range, 2.2 - 6.9 yrs) with premature sexual development which fitted neither diagnostic category. Features characteristic of IPT were absent pubic hair (n=6), fluctuating breast size (n=4), a small uterus on ultrasound without an endometrial echo (n=6). Features more consistant with CPP were accelerated growth (n=5) and progressive breast enlargement (n=2). Ovarian ultrasound morphology showed that all 6 girls had ovaries containing large numbers of small cysts between 3 - 4 mm in diameter. 5 girls had predominant FSH response to i/v GnRH. The results of overnight serum gonadotrophin secretion were not typical of CPP or IPT. Discrete LH and FSH pulses were seen with neither prcdominating. 5 girls were treated unsuccessfully with intranasal (D-Ser6) GnRH but 2 girls responded to subcutaneous administration. 2 girls had spontaneous regression of breast development after intranasal therapy ceased. We believe that our patients represent a spectrum between IPT and CPP which is relevant for prognosis and treatment as well as for understanding disorders of ovarian maturation.

Pulsatile GnRH treatment of the ovariectomized rat and release of LH and FSH.

The effect of pulsatile GnRH administration on the levels of LH and FSH was investigated in rats that had been ovariectomized 2 weeks earlier. Also the asynchronous occurrence of endogenous and GnRH-induced LH and FSH pulses was analysed. A small pulse dose of GnRH (1.25 ng/100 g) was given iv at a frequency of once every 60 min or once every 120 min during 24 h. A larger dose of 5 ng/100 g was given once every 60 or 120 min during either 24 h or 96 h. Blood was sampled arterially every 5 min around the two first and last GnRH injections and LH and FSH were measured. Only the treatment with the larger GnRH pulse dose resulted in a change of LH and FSH plasma levels. LH levels declined under all circumstances, whereas FSH was found to be increased temporarily after 24 h of treatment. The pituitary LH response to pulses of GnRH (5 ng/100 g) decreased irrespective of the frequency or duration with which GnRH was administered. There was a marked asynchronicity between LH and FSH pulses and almost every injection of GnRH (5 ng/100 g) resulted in clear LH pulses but not in FSH pulses.

Alterations in the pulsatile properties of gonadotropin secretion in alcoholic men.

The functional characteristics of the hypothalamic-pituitary-testicular axis were examined quantitatively in 10 chronic alcoholic men without hepatic dysfunction or clinical nutritional deficiencies. Spontaneous gonadotropin pulsatility was analyzed in blood sampled every 20 minutes over a 24-hour period 3 to 16 days after abstinence from alcohol and again 29 to 39 days later. The numbers of LH and FSH pulses per 24 hours were normal in these alcoholic men compared with controls. However, we found increased mean 24-hour concentrations of immunoactive LH (P = 0.012) and FSH (P = 0.018), increased peak heights for LH (P = 0.035) and FSH (P = 0.004), decreased fractional LH (P = 0.002) and FSH (P = 0.044) pulse amplitudes and increased interpulse valley mean LH (P = 0.010) and FSH (P = 0.018) concentrations. Serum levels of total testosterone, total estradiol and estrone were normal, whereas concentrations of free testosterone and free estradiol were increased. Pituitary release of LH and FSH was normal in response to low (5-micrograms) and high (95-micrograms) doses of GnRH given intravenously. The present observations indicate that in chronically alcoholic men, acute abstinence from ethanol is associated with elevated circulating concentrations of immunoactive gonadotropins in the presence of intact spontaneous gonadotropin pulsatility, preserved pituitary responsiveness to exogenous GnRH, and increased concentrations of free testosterone and free estradiol. Such findings are consistent with alterations in the endogenous feedback actions of sex steroid hormones in this setting.