Gonadotropin pulsatile secretion in girls with premature menarche

Five prepubertal girls (2.3-8.1 years old) were studied for isolated or recurrent vaginal bleeding in the absence of other signs of precocious puberty (premature menarche). Four of these girls with recurrent vaginal bleeding were studied for pulsatile gonadotropin secretory patterns. During sleep 3 girls showed luteinizing hormone (LH) pulses with low amplitude and a pubertal pattern of frequency whereas follicle-stimulating hormone (FSH) increased without demonstrable episodic secretion. Luteinizing hormone-releasing hormone (LHRH) tests demonstrated that FSH responses are greater than the LH responses, as in prepuberty. In 3 cases estradiol levels had augmented above normal prepubertal range. The menses spontaneously stopped during the follow-up. A reevaluation of the gonadotropin pattern, having the menses stopped for 6 months, in one of the girls with pulsatile LH secretion showed an apulsatile prepubertal LH pattern. Also estradiol levels returned to prepubertal range. A follow-up of 10-66 months of these patients did not show any growth and bone acceleration or signs of precocious puberty. Our data suggest that in premature menarche a partial and transient activation of hypothalamo-pituitary axis could be present. Premature menarche seems to be a benign and self-limiting condition and one of the girls had a normal onset of puberty during follow-up.     

Changes in circulating levels of immunoreactive follicle stimulating hormone, luteinizing hormone, and testosterone during sexual development in the rhesus monkey, Macaca mulatta

Basal serum levels of follicle stimulating hormone (FSH), luteinizing hormone (LH), and testosterone (T) and the responsiveness of these hormones to a challenge dose of luteinizing hormone releasing hormone (LHRH), were determined in juvenile, pubertal, and adult rhesus monkeys. The monkey gonadotrophins were analyzed using RIA reagents supplied by the World Health Organization (WHO) Special Programme of Human Reproduction. The FSH levels which were near the assay sensitivity in immature monkeys (2.4 +/- 0.8 ng/ml) showed a discernible increase in pubertal animals (6.4 +/- 1.8 ng/ml). Compared to other two age groups, the serum FSH concentration was markedly higher (16.1 +/- 1.8 ng/ml) in adults. Serum LH levels were below the detectable limits of the assay in juvenile monkeys but rose to 16.2 +/- 3.1 ng/ml in pubertal animals. When compared to pubertal animals, a two-fold increase in LH levels paralleled changes in serum LH during the three developmental stages. Response of serum gonadotrophins and T levels to a challenge dose of LHRH (2.5 micrograms; i.v.) was variable in the different age groups. The present data suggest: an asynchronous rise of FSH and LH during the pubertal period and a temporal correlation between the testicular size and FSH concentrations; the challenge dose of LHRH, which induces a significant rise in serum LH and T levels, fails to elicit an FSH response in all the three age groups; and the pubertal as compared to adult monkeys release significantly larger quantities of LH in response to exogenous LHRH.     

Treatment of precocious puberty with a long-acting preparation of D-Trp6-LHRH

D-Trp6-LHRH was tested in 6 girls 1-8 years old and 7 boys 2-10 years old with precocious puberty. All children had advanced bone age, breast or testis enlargement and a pubertal LH response to LHRH. 60 micrograms LHRH-A/kg body weight was given intramuscularly on days 1 and 21 and thereafter every 4 weeks for 6-21 months. In girls, breast enlargement disappeared and mean uterus size decreased within 6 months. Mean ovary length decreased from 25.0 +/- 1.9 to 16.0 +/- 2.7 (p less than 0.02). In boys, mean testis volume decreased from 8.0 +/- 1.1 to 6.7 +/- 1.4 ml (p less than 0.05) within 6 months. In both sexes, growth velocity decreased significantly and bone maturation was reduced. Plasma levels of estradiol or testosterone and FSH levels decreased significantly within 3 weeks. The LH response to LHRH was reduced to normal prepubertal values after 7 weeks. No secondary clinical or biochemical escape occurred. No side effects occurred except for transient vaginal bleeding in one girl after the first and second injection. No antibodies to LHRH-A were detected in the patients' sera. This study demonstrates the ability of a delayed release formulation of D-Trp6-LHRH to suppress pituitary and gonadal secretion and pituitary response to LHRH for as long as 2 years of therapy. This treatment appears to be more efficient in treating both clinical and biochemical abnormalities than does treatment with inhibitory steroids. Additionally the method of administration is more practical and ensures better patient compliance.     

Pulsatile infusion of luteinizing hormone-releasing hormone induces precocious puberty (vaginal opening and first ovulation) in the immature female guinea pig

Previously we have hypothesized that an increase in luteinizing hormone-releasing hormone (LHRH) due to hypothalamic maturation is the key factor controlling the onset of puberty. This led to the working hypothesis that precocious puberty would be induced if LHRH is administered with an appropriate protocol. Thus, effects of pulsatile infusion of LHRH on the onset of first vaginal opening and first ovulation in immature female guinea pigs were studied. Luteinizing hormone-releasing hormone in hourly pulses of either 5 ng or 50 ng was infused through a chronically implanted jugular catheter for 9-29 days starting at 20 days of age. For the control experiment saline was infused in a similar manner. Infusion of 5 ng LHRH/h resulted in significantly earlier (P less than 0.001) ages at first vaginal opening (24.7 +/- 0.9 days) and at first ovulation (28.8 +/- 0.9 days) compared to saline controls (first vaginal opening 53.3 +/- 6.8 days; first ovulation 55.2 +/- 6.5 days). Infusion with a 10-fold higher LHRH dose (50 ng/h) also advanced the age at first vaginal opening (25.3 +/- 0.7 days), but precocious ovulation was no longer induced (53.7 +/- 5.3 days). Interestingly, LHRH infusion with the high dose resulted in a prolonged period of vaginal opening and cornification without ovulation. These results indicate that 1) pulsatile infusion of a small amount of LHRH with a constant frequency induces precocious puberty in a laboratory rodent, and 2) infusion of LHRH with a dose higher than the effective dose for the induction of early puberty results in a persistent estrous anovulatory syndrome. Therefore, the present study not only supports our hypothesis that an increase in endogenous LHRH release is responsible for the onset of puberty, but also further suggests that excessive release of LHRH or abnormal patterns of LHRH release may be involved in the etiology of the anovulatory persistent estrus syndrome.     

Low serum allopregnanolone levels in girls with precocious pubarche

Allopregnanolone, a neuroactive steroid, increases during pubertal development and high concentrations are present in subjects with precocious puberty. The aim of the present study was to evaluate serum allopregnanolone levels in girls with precocious pubarche (PP). Basal gonadotropins and steroid hormones were assessed in 17 girls with PP, 22 girls with central precocious puberty (CPP), 25 girls with normal puberty at the same pubertal stage of CPP ones, and 17 prepubertal girls. Adrenocorticotropin hormone (ACTH) and gonadotropin-releasing hormone (GnRH) stimulation tests were performed in all subjects with PP, and in 12 out of 22 with CPP. All girls with normal puberty underwent to GnRH test, while ACTH test was performed in 17 out of 25. Basal dehydroepiandrosterone sulfate (DHEAS) concentrations resulted significantly higher in PP and normal pubertal girls than in prepubertal ones. Allopregnanolone, gonadotropins and estradiol levels were significantly lower in PP group with respect to CPP (P<0.05), while they were comparable among PP, normal pubertal and prepubertal groups. After ACTH administration, allopregnanolone concentrations significantly increased in all groups (P<0.05). After GnRH stimulation, its levels significantly increased in CPP and normal pubertal controls (P<0.05), while no incremental rise was found in PP girls. In conclusion, our study shows that in girls with PP basal and GnRH-stimulated levels of allopregnanolone are significantly lower than in CPP girls. These data suggest that this neurosteroid may be considered a new marker of pubertal development.     

Treatment of central precocious puberty with an LHRH agonist (Buserelin): effect on growth and bone maturation after three years of treatment

The LHRH analog Buserelin was used to treat 27 children (21 girls, 6 boys) with central precocious puberty. Nineteen patients had idiopathic precocious puberty and 8 had organic lesions (hamartoma, hydrocephalus or suprasellar arachnoid cyst). All patients received 20 or 30 micrograms/kg/day s.c. of Buserelin, and we obtained plasma E2 less than 20 pg/ml, vaginal maturation index less than 30 in girls or plasma testosterone less than 0.3 ng/ml in boys. The mean growth rate decreased from 9.3 +/- 0.5 to 4.6 +/- 1.3 cm/year after 3 years. The velocity of skeletal maturation decreased so that the final height prediction improved by a mean value of 1.6 SD. As the follow-up increases, this study confirms that LHRHa therapy is effective and potentially improves the final height of children presenting active and severe central precocious puberty.     

Reduced growth hormone secretion prolongs puberty but does not delay the developmental increase in luteinizing hormone in the absence of gonadal negative feedback

Previous studies have shown that the growth hormone (GH) axis is important for timing the later stages of puberty in female monkeys. However, it is not clear whether these growth-related signals are important for the initiation of puberty and early pubertal events. The present study, using female rhesus monkeys, used two approaches to answer this question. Experiment 1 tested the hypothesis that reduced GH secretion would blunt the rise in nocturnal LH secretion in young (17 mo; n = 7) but not older adolescent ovariectomized females (29 mo; n = 6). Reduced GH secretion was induced by treating females with the sustained release somatostatin analogue formulation, Sandostatin LAR (625 microg/kg). Morning (0900-0930 h) and evening (2200-2230 h) concentrations of bioactive LH were higher in older adolescent compared to young adolescent females. However, diurnal concentrations were not affected by the inhibition of GH secretion in either age group when compared to the placebo-treated, control condition. Experiment 2 tested the hypothesis that reduced GH secretion induced in young juvenile females would delay the initial increase in nocturnal LH secretion and subsequent early signs of puberty. In order to examine this hypothesis, puberty in control females (n = 7) was compared to those in which puberty had been experimentally arrested until a late adolescent age (29 mo) by the use of a depot GnRH analogue, Lupron (750 microg kg(-1) mo(-1); n = 7). Once the analogue treatment was discontinued, the progression of puberty was compared to a group treated in a similar fashion but made GH deficient by continuous treatment with Sandostatin LAR (n = 6). Puberty occurred as expected in control females with the initial rise in evening LH at 21 mo, menarche at 22 mo, and first ovulation at 30 mo. As expected, Lupron arrested reproductive maturation, but elevations in morning and evening LH and menarche occurred within 2 mo of the cessation of Lupron in both Lupron and Lupron-GH-suppressed females. In contrast, first ovulation was delayed significantly in the Lupron-GH-suppressed females (41 mo) compared to the Lupron-only females (36 mo). These data indicate that within this experimental model, reduced GH secretion does not perturb the early stages of puberty but supports previous observations that the GH axis is important for timing the later stages of puberty and attainment of fertility. Taken together, the data indicate that factors that reduce GH secretion may have a deleterious effect on the completion of puberty.     

Long-term results of long-acting luteinizing-hormone-releasing hormone agonist in central precocious puberty.

Thirty children with precocious puberty (24 girls aged 6.5 +/- 2.3 years and 6 boys aged 7 +/- 2.9 years) were treated over 5 years with Decapeptyl. In girls, the menses disappeared, breast enlargement regressed, and uterus and ovary sizes returned to prepubertal values. In boys, a significant decrease of testicular size was observed. Plasma levels of estradiol and testosterone, and basal and post-luteinizing hormone (LH)-releasing hormone (LHRH) LH and follicle-stimulating hormone (FSH) remained in the prepubertal range. Growth velocity decreased after 1 year from 9.7 +/- 3.5 to 5.5 +/- 1.3 cm/year, while the height age/bone age ratio was normalized in both sexes after 3 years. In 15 girls, Decapeptyl was interrupted after 2.3 years. During those 2.3 years, bone age increased from 11.6 +/- 0.8 to 12.5 +/- 0.7 years with a growth velocity of 5.3 +/- 1.8 cm/year. During the year following interruption, height increased from 152.2 +/- 4.9 to 157.7 +/- 4.9 cm (growth velocity 5.5 cm/year) and bone age from 12.5 +/- 0.7 to 13.5 +/- 0.6 years. One year after treatment, plasma levels of estradiol were 106.7 +/- 84.7 pg/ml, of LH, 25.5 +/- 17.6 mIU/ml, and of FSH, 10.8 +/- 5.9 mIU/ml. Menses appeared in 13 girls. Moreover, 18 months after interruption, bone age was 13.9 +/- 0.6 years and height 159.5 +/- 5.2 cm, being significantly superior to the final height of a historical control group: 151.5 +/- 4.8 cm (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)     

The role of endogenous gonadotropin-releasing hormone in the control of luteinizing hormone and testosterone secretion in the juvenile male monkey, Macaca fascicularis

To determine what changes occur in the activity of gonadotropin-releasing hormone (GnRH) neurons during pubertal development in primate species we tested the hypotheses that there are morphologic differences between GnRH-containing neurons in juvenile versus adult monkeys, and the low activity of the reproductive axis is governed by hypothalamic GnRH release in monkeys prior to puberty. We removed the brains from 5 juvenile and 5 adult male monkeys (Macaca fascicularis) and blocked, sectioned, and prepared each hypothalamus for light microscopic immunocytochemistry for GnRH-containing cells. The distribution and number of GnRH-containing neurons were similar in adult and juvenile brains; however, GnRH-containing perikarya in adult brains were significantly larger in total cross-sectional area (200 +/- 12 vs. 169 +/- 8 micron 2, P less than 0.05) and in cross-sectional area of the cytoplasm (139 +/- 2 vs. 88 +/- 6 micron 2, P less than 0.05) than in juvenile brains. In another group of 10 juvenile male macaques, we administered an antiserum to GnRH (Fraser #94; 2 ml/kg, i.v.) and monitored the effects on plasma luteinizing hormone (LH) and testosterone concentrations. The percentage of plasma samples with detectable LH levels decreased significantly (from 26.67 +/- 8.3% to 5.3 +/- 3.4%, P less than 0.05) after GnRH antiserum administration; however, plasma testosterone concentrations (0.08 +/- 0.02 ng/ml) remained unchanged. We conclude that during pubertal maturation in primate species there is increased synthesis and release of GnRH from a population of GnRH neurons that are active prior to puberty.     

Testosterone modulates the differential release of luteinizing hormone and follicle-stimulating hormone that occurs in response to changing gonadotropin-releasing hormone pulse frequency in the male monkey, Macaca fascicularis

Selective elevations of plasma follicle-stimulating hormone (FSH) levels are characteristic of some physiological conditions, such as the early stages of human puberty, and in some disorders of testicular function, such as idiopathic oligospermia. We tested the hypotheses that a slow gonadotropin-releasing hormone (GnRH) pulse frequency favors a selective elevation of plasma FSH and that this is influenced by the circulating steroidal milieu. We administered exogenous GnRH at frequencies of once every 90 min (q 90 min) and once every 240 min (q 240 min) to castrated prepubertal male monkeys who had received either empty (sham) or testosterone (T)-filled Silastic capsules at the time of castration. At the end of each experimental frequency period, mean plasma levels of luteinizing hormone (LH) and FSH were measured. Plasma T levels were also measured. Animals with T implants had plasma levels of this hormone that were in the adult range (approximately equal to 8 ng/ml), whereas those with sham implants had plasma T levels in the prepubertal range (less than or equal to 4 ng/ml). In animals with sham implants, mean plasma FSH levels were markedly elevated at the slower GnRH pulse frequency (39.5 +/- 3.6 ng/ml following GnRH q 240 min compared with 23.7 +/- 2.8 ng/ml following GnRH q 90 min). This selective FSH elevation was not apparent in animals with T implants. Mean plasma LH levels were similar (approximately equal to 8 micrograms/ml) at the two GnRH pulse frequencies, in both T-treated and sham-implanted animals.(ABSTRACT TRUNCATED AT 250 WORDS)     

Induction of the self-priming effect of luteinizing hormone releasing hormone during the sexual maturation of the male rat

Pubertal and young adult male rats release more luteinizing hormone (LH) in response to luteinizing hormone releasing hormone (LHRH) if pretreated with LHRH than if pretreated with saline. Immature male rats do not show this self-priming effect. In order to examine the role of acute changes in testicular steroids in this process, immature (29-30 days old) or pubertal (50-51 days old) male rats were castrated or sham operated under ketamine HCl anesthesia. Beginning immediately after completion of the surgery, they were given three priming injections of 10 ng LHRH/100 g body wt or saline at 30-min intervals. Thirty minutes after the third priming injection, a blood sample was obtained by cardiac puncture followed immediately by a challenge injection of 50 ng LHRH/100 g body wt given to both saline and LHRH primed groups. Ten minutes after the challenge injection a final blood sample was obtained by heart puncture. Serum was assayed for LH concentration by radioimmunoassay. Sham-operated pubertal rats showed a typical self-priming effect. Animals pretreated with LHRH released significantly (P less than 0.01) more LH in response to the challenge injection than did rats pretreated with saline. Acute castration also resulted in a significant (P less than 0.001) self-priming effect in pubertal rats. As anticipated, sham castrated immature males did not show a self-priming effect. Acutely castrated immature rats however, showed a significant (P less than 0.05) self-priming effect. These data provide support for the hypothesis that, prior to puberty, increases in testosterone during the priming process inhibit the expression of the self-priming effect.     

Munc18 plays an important role in the regulation of glutamate release during female puberty onset

Munc18, a mammalian homolog of C. elegans Unc, is essential for neurotransmitter release. The aim of this study was to identify estrogen-dependent expression of Munc18-1 and its role in the regulation of glutamate release for puberty onset. Hypothalamic munc18-1 mRNA levels were significantly increased by estrogen treatment in ovariectomized, immature female rats. During pubertal development, the munc18-1 mRNA levels dramatically increased between the juvenile period and the anestrous phase of puberty. Intracerebroventricular administration of an antisense oligodeoxynucleotide against munc18-1 mRNA significantly decreased glutamate release and delayed the day of puberty onset. These results suggest that Munc18-1, expressed in an estrogen-dependent manner, plays an important role in the onset of female puberty via the regulation of glutamate release.     

Diagnostic utility of a low-dose gonadotropin-releasing hormone test in the context of puberty disorders

OBJECTIVES: The 10-microg gonadotropin-releasing hormone (GnRH) test assesses pituitary gonadotroph responsiveness, whereas the 100-microg dose assesses maximal secretory capacity. Our aims were to establish normative data for the low-dose test in children and to evaluate the test in diagnosing common pubertal disorders. METHODS: We retrospectively classified 107 children who underwent 10-microg GnRH tests into normal prepubertal (20 boys, 10 girls), normal early pubertal (10 boys, 16 girls), constitutional delay of puberty (CDP, 13 prepubertal boys >12 years), hypogonadotropic hypogonadism (HH, 5 prepubertal boys >12 years), central precocious puberty (CPP, 19 girls) or premature thelarche/variant (13 girls). RESULTS: Peak LH response was higher in prepubertal boys >12 years compared with younger boys (p < 0.01) but showed no further change in early puberty. CDP boys had LH responses similar to prepubertal boys >12 years. HH boys showed an absent LH response which diagnosed HH with 100% sensitivity and 96% specificity. Thelarche girls had LH:FSH peak ratios lower than normal prepubertal (p = 0.001), pubertal (p < 0.05) or CPP (p = 0.001) girls. CONCLUSIONS: We have established normative values for the low-dose GnRH test in children. The test successfully differentiated HH from CDP in boys, and contributed to the differential diagnosis of CPP and premature thelarche in girls.     

GABA对大鼠下丘脑正中隆起LHRH释放调节的研究

本研究应用大鼠下丘脑正中隆起(ME),观察 γ-氨基丁酸(GABA)和去甲肾上腺素(NA)对下丘脑促黄体生成激素释放激素(LHRH)神经元末梢分泌作用的影响。结果发现:GABA(10~(-6)mol/L)可显著促进 ME 的 LHRH 和 NA 的释放,即 LHRH 释放量由27.3±2.5pg/100ul 增加至150.4±27.9pg/100μl;NA 释放量由50.9±4.2pg/100μl 增加至105.5±19.1pg/100ul,两者与对照组相比有显著差异(P<0.01)。GABA 这些作用可被受体拮抗剂荷包牡丹碱(Bicuculline)所翻转。当荷包牡丹碱和 GABA(10~(-6)mol/L)同时存在于 ME 的培灌液中,LHRH 的分泌量下降为18.2±1.9pg/100μl,而 NA 分泌量下降为43.9±3.4pg/100μl。在内源性 NA 被利血平耗竭时,LHRH 的释放量仅增加26.5%,而 GABA 能使正常大鼠 LHRH 释放量增加451.9%。本研究提示:GABA 可促进下丘脑 ME 释放 LHRH,这一作用可能通过 NA 中介。     

Growth, bone maturation and height prediction after three years of therapy with the slow release GnRH-agonist Decapeptyl-Depot in children with central precocious puberty.

More than 100 patients with central precocious puberty are participating in this international multicenter study using monthly i.m. injections of the slow-release GnRH agonist Decapeptyl-Depot. In 15 patients, Decapeptyl-Depot treatment could be discontinued after 2 years of therapy. Gonadal suppression was promptly reversible in all of them, as shown by prepubertal low gonadotrophin- and sex steroid levels. Of the remaining 90 patients, 40 have been treated for more than 3 years, including 33 girls and 7 boys. Plasma levels of LH, FSH, estradiol and testosterone dropped to the prepubertal range after one month of Decapeptyl-Depot and remained there for the whole period of therapy. At start of therapy, mean chronologic age of these 40 children was 6.6 +/- 1.4 (SD) years, mean bone age 10.2 +/- 1.9 years. Mean predicted adult height increased in the boys from 173.6 +/- 13.8 (SD) cm at start of therapy to 184.6 +/- 17.0 cm after 3 years. Predicted adult height increased in girls from 158.0 +/- 12.2 to 161.0 +/- 7.5 cm. Undue side effects were not seen, long term tolerance was good. It is concluded that Decapeptyl-Depot injected i.m. every 4 weeks suppresses the pituitary-gonadal axis in children with central precocious puberty without clinical or biochemical escapes, and leads to an increase in predicted adult height by more than 3 cm in all boys and in 53% of the girls after three years of treatment.     

Correlation of hypothalamic LHRH, pituitary LH and plasma LH in developing rats.

Hypothalamic LHRH, pituitary LH and plasma LH levels were measured in rats of both sexes from day 5-60 after birth. The content of hypothalamic LHRH was very high in one-week-old male and female rats. It declined gradually till day 17 in the female rat and sharply on day 10 in the male rat. Subsequently the content of hypothalamic LHRH increased and showed peak values on day 25 in the female rat and on day 45 in the male rat. It decreased markedly at respective times of puberty in both sexes (day 37 in the female rat and day 52-60 in the male rat). Results of the study suggest that maturation of hypothalamo-hypophyseal-axis proceeds in three distinct stages. Observations on days 17, 25 and 37 in the female rat and on days 5, 7, 10 and 22 in the male rat clearly show an inverse relationship between hypothalamic LHRH and plasma LH and a parallel relationship between pituitary and plasma LH. Marked decline in the content of hypothalamic LHRH at respective times of puberty in both sexes indicates that the release of threshold levels of LHRH from the hypothalamus may apparently be the event initiating the pubertal changes in rat.     

Delay in the age of balano-preputial skinfold cleavage and alterations in serum profiles of testosterone, 5 alpha-androstane-3 alpha,17 beta-diol, and gonadotropins in adult rats treated during puberty with luteinizing hormone releasing hormone

Previous work has shown that chronic treatment of intact, immature male rats with luteinizing hormone releasing hormone (LHRH) decreases sex accessory gland weights and results in retardation of the normal developmental increase in the ratio of serum testosterone (T)/5 alpha-androstane-3 alpha,17 beta-diol (3 alpha-Diol) via an apparent enhancement of testicular 5 alpha-reductase or 3 alpha-hydroxysteroid oxidoreductase activities. In the present work, androgen dependent balano-preputial skinfold cleavage was significantly delayed by approximately one week in intact, immature male rats which were treated daily for two weeks with either 1.0 micrograms, 2.5 micrograms or 5.0 micrograms of LHRH during a discrete phase of pubertal development (28-41 days of age). In intact, adult (62 day old) animals which received LHRH treatments during pubertal development, serum T concentrations and sex accessory gland weights were reduced compared to control animal values. Serum 3 alpha-Diol content in the adult rats was either unaltered or increased significantly depending on the LHRH dosage employed during sexual development. Serum luteinizing hormone concentrations were not different between control and LHRH-pretreated adult rats whereas the highest dosage of LHRH employed (5.0 micrograms) during puberty resulted in a significant elevation of adult serum follicle stimulating hormone levels. It is suggested that chronic LHRH treatment of the male rat during puberty results in a perturbation in testicular androgen biosynthetic activities and an impairment of pituitary-testicular hormone feedback mechanisms which persist at least through early adulthood.     

Relation between nocturnal melatonin profile and hormonal markers of puberty in humans.

We examined the relation between nocturnal melatonin and hormonal markers of puberty in 57 normal children and adolescents and 39 subjects with disorders of pubertal onset. Melatonin was measured in hourly blood samples drawn overnight by constant withdrawal. Basal 08.00 h plasma testosterone, estradiol and LH, and the peak LH response to LHRH administration were determined. There were no significant correlations between testosterone, estradiol, basal LH and peak LH and melatonin peak (r = -0.18, -0.22, -0.02, -0.12, respectively) or melatonin peak time (r = 0.12, -0.01, -0.02, 0.07 respectively). The results were not affected significantly by sex, diagnosis or age. A comparison of subjects grouped by peak LH < 15 U/l (most likely prepubertal; n = 40) and peak LH > 30 U/l (most likely pubertal; n = 34) showed no significant differences in melatonin peak (160.5 +/- 59.3 vs. 146.6 +/- 50.9 pg/ml; t = 1.09; p > 0.05) or melatonin peak time (1.8 +/- 1.7 vs. 2.5 +/- 1.7 h; t = -1.79; p > 0.05). Although a pineal-puberty relation cannot be excluded, the results do not support the hypothesis that melatonin restrains the hypothalamic-pituitary-gonadal axis during childhood.     

The involvement of boar submaxillary salivary gland secretions in boar-induced precocious puberty attainment in the gilt

The involvement of secretions from boar submaxillary salivary glands in mediating the induction of precocious puberty in the gilt was investigated as follows. Forty-eight Large White × (Large White × Landrace) prepubertal gilts from 12 litters were randomly allocated within litters by weight, to four treatment groups of six, in two replicates, at 145 days of age. Treatments commencing at a mean group age of 165 days, were: (1) control (no boar exposure); (2) gilts exposed to a mature sialectomised boar (submaxillary salivary glands were removed at 9 weeks of age); (3) gilts exposed to a mature sham-operated boar; (4) gilts exposed to a mature unoperated boar.Boar exposure occurred for 30 min per day for 75 days, or until pubertal oestrus was observed. Gilts showing pubertal oestrus were removed and slaughtered. Ovaries were examined to confirm reproductive status. Gilts failing to exhibit oestrus by 240 days of age were slaughtered and nominally ascribed a pubertal age of 245 days. Age at puberty was significantly earlier in all three boar-exposed treatments than in the control treatment (P<0.05 for treatments 2 and 3, P<0.001 for treatment 4; median ages at puberty being 227.0, 203.5 , 202.0 and 179.0 days for treatments 1 to 4 respectively). No frothy saliva was ever produced by the sialectomised boar, and chromatographic analysis of saliva produced by the sham-operated boar during mating revealed very low levels of 16-androstene pheromones, while levels in the unoperated boar's saliva were normal. These results provide further evidence for an important role of boar salivary pheromones in the induction of precocious puberty attainment in the gilt.     

The role of estrogen in bone growth and maturation during childhood and adolescence

Twenty years ago it was believed that pubertal growth was stimulated by testicular androgen in boys and by adrenal androgen in girls. Estrogen, which was used to inhibit growth in excessively tall girls, was not thought to have growth-promoting effects. We hypothesized that estrogen has a biphasic effect on epiphyseal growth, with maximal stimulation at low levels. We showed that the administration of low doses of estrogen, corresponding to a serum estradiol level of about 4 pg/ml (15 pmol/l) caused more than a 60% increase over the prepubertal growth rate in both boys and girls. To test the hypothesis that estrogen is the principal mediator of the pubertal growth spurt in boys, we administered the aromatase inhibitor, testolactone, to boys with familial male-limited precocious puberty. Testolactone produced near normalization of both growth velocity and bone maturation, despite levels of serum testosterone that remained within the adult male range. The observation that low levels of estrogen stimulate growth and bone maturation suggested that estrogen might explain the more rapid epiphyseal maturation of prepubertal girls compared to boys. To determine whether prepubertal girls have higher estrogen levels than prepubertal boys, we developed an ultrasensitive recombinant cell bioassay for estrogen with a sensitivity of 0.02 pg/ml (0.07 pmol/l) estradiol equivalents. Prepubertal girls had approximately eight-fold higher levels of serum estradiol than did prepubertal boys (0.6 ± 0.6 pg/ml (SD) (2.2 ± 2.2 pmol/l) vs 0.08 ± 0.2 pg/ml (0.29 ± 0.73 pmol/l), P < 0.05). We concluded that the pubertal growth spurt of both sexes is driven primarily by estrogen, and that the more rapid epiphyseal maturation of prepubertal girls (vs boys) may be explained by their higher estradiol levels.