Luteinizing hormone and follicle stimulating hormone secretion patterns in girls throughout puberty measured using highly sensitive immunoradiometric assays

Central precocious puberty: a review of diagnosis, treatment, and outcomes

Central precocious puberty (CPP) refers to early activation of the hypothalamic-pituitary-gonadal (HPG) axis and is manifested by breast development in girls or testicular enlargement in boys before the normal physiological age ranges. CPP can be precipitated by intracranial pathology, exposure to high levels of sex steroids, or environmental risk factors, but most cases are idiopathic. Monogenic causes have also been identified. In this Review, we summarise pathophysiology, risk factors, diagnosis, and management of CPP. Concern for CPP should prompt referral to paediatric endocrinology where diagnosis is confirmed by clinical, biochemical, radiological, and genetic testing. CPP is treated with a gonadotropin-releasing hormone analogue, the primary aims of which are to increase adult height and postpone development of secondary sexual characteristics to an age that is more commensurate with peers. Although long-term outcomes of treatment with gonadotropin-releasing hormone analogues are reassuring, additional research on the psychological effect of CPP is needed.

The mechanism underlying the pubertal increase in pulsatile GnRH release in primates

In primates, the gonatotropin-releasing hormone (GnRH) neurosecretory system, consisting of GnRH, kisspeptin, and neurokinin B neurons, is active during the neonatal/early infantile period. During the late infantile period, however, activity of the GnRH neurosecretory system becomes minimal as a result of gonadal steroid independent central inhibition, and this suppressed GnRH neurosecretory state continues throughout the prepubertal period. At the initiation of puberty, the GnRH neurosecretory system becomes active again because of the decrease in central inhibition. During the progress of puberty, kisspeptin and neurokinin B signaling to GnRH neurons further increases, resulting in the release of gonadotropins and subsequent gonadal maturation, and hence puberty. This review further discusses potential substrates of central inhibition and subsequent pubertal modification of the GnRH neurosecretory system by the pubertal increase in steroid hormones, which ensures the regulation of adult reproductive function.

Interpretation of reproductive hormones before, during and after the pubertal transition-Identifying health and disordered puberty

Puberty is a process of transition from childhood to adult reproductive capacity, governed by the reactivation of the hypothalamic-pituitary-gonadal axis after a long period of dormancy in mid-childhood. As such, the reproductive hormones are in a state of flux during the adolescent years, and interpretation of both the onset of healthy, concordant puberty and the differentiation of precocious, delayed or disordered puberty, can be challenging. This review is focused on the description of the endocrine axes in healthy puberty and the markers of disorders of puberty that can aid diagnosis and management for patients with these conditions. It will cover the hypothalamic, pituitary and gonadal hormone systems, the dynamic changes that occur during puberty, conditions leading to precocious, delayed or absent puberty and other syndromes with disordered puberty, and the biochemical diagnosis of these different disorders of puberty.

Hormone References for Ultrasound Breast Staging and Endocrine Profiling to Detect Female Onset of Puberty

CONTEXT

Application of ultrasound (US) to evaluate attainment and morphology of glandular tissue provides a new rationale for evaluating onset and progression of female puberty, but currently no hormone references complement this method. Furthermore, previous studies have not explored the predictive value of endocrine profiling to determine female puberty onset.

OBJECTIVE

To integrate US breast staging with hypothalamic-pituitary-gonadal hormone references and test the predictive value of an endocrine profile to determine thelarche.

DESIGN SETTING AND PARTICIPANTS

Cross-sectional sample of 601 healthy Norwegian girls, ages 6 to 16 years.

MAIN OUTCOME MEASURES

Clinical and ultrasound breast evaluations were performed for all included girls. Blood samples were analyzed by immunoassay and ultrasensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) to quantify estradiol (E2) and estrone (E1) from the subpicomolar range.

RESULTS

References for E2, E1, luteinizing hormone, follicle-stimulating hormone, and sex hormone-binding globulin were constructed in relation to chronological age, Tanner stages, and US breast stages. An endocrine profile index score derived from principal component analysis of these analytes was a better marker of puberty onset than age or any individual hormone, with receiver-operating characteristic area under the curve 0.91 (P < 0.001). Ultrasound detection of nonpalpable glandular tissue in 14 out of 264 (5.3%) girls with clinically prepubertal presentation was associated with significantly higher median serum levels of E2 (12.5 vs 4.9 pmol/L; P < 0.05) and a distinct endocrine profile (arbitrary units; P < 0.001).

CONCLUSIONS

We provide the first hormone references for use with US breast staging and demonstrate the application of endocrine profiling to improve detection of female puberty onset.

Pubertal Hormonal Changes and the Autonomic Nervous System: Potential Role in Pediatric Orthostatic Intolerance

Puberty is initiated by hormonal changes in the adolescent body that trigger physical and behavioral changes to reach adult maturation. As these changes occur, some adolescents experience concerning pubertal symptoms that are associated with dysfunction of the autonomic nervous system (ANS). Vasovagal syncope (VVS) and Postural Orthostatic Tachycardia Syndrome (POTS) are common disorders of the ANS associated with puberty that are related to orthostatic intolerance and share similar symptoms. Compared to young males, young females have decreased orthostatic tolerance and a higher incidence of VVS and POTS. As puberty is linked to changes in specific sex and non-sex hormones, and hormonal therapy sometimes improves orthostatic symptoms in female VVS patients, it is possible that pubertal hormones play a role in the increased susceptibility of young females to autonomic dysfunction. The purpose of this paper is to review the key hormonal changes associated with female puberty, their effects on the ANS, and their potential role in predisposing some adolescent females to cardiovascular autonomic dysfunctions such as VVS and POTS. Increases in pubertal hormones such as estrogen, thyroid hormones, growth hormone, insulin, and insulin-like growth factor-1 promote vasodilatation and decrease blood volume. This may be exacerbated by higher levels of progesterone, which suppresses catecholamine secretion and sympathetic outflow. Abnormal heart rate increases in POTS patients may be exacerbated by pubertal increases in leptin, insulin, and thyroid hormones acting to increase sympathetic nervous system activity and/or catecholamine levels. Given the coincidental timing of female pubertal hormone surges and adolescent onset of VVS and POTS in young women, coupled with the known roles of these hormones in modulating cardiovascular homeostasis, it is likely that female pubertal hormones play a role in predisposing females to VVS and POTS during puberty. Further research is necessary to confirm the effects of female pubertal hormones on autonomic function, and their role in pubertal autonomic disorders such as VVS and POTS, in order to inform the treatment and management of these debilitating disorders.

Delayed Puberty-Phenotypic Diversity, Molecular Genetic Mechanisms, and Recent Discoveries

This review presents a comprehensive discussion of the clinical condition of delayed puberty, a common presentation to the pediatric endocrinologist, which may present both diagnostic and prognostic challenges. Our understanding of the genetic control of pubertal timing has advanced thanks to active investigation in this field over the last two decades, but it remains in large part a fascinating and mysterious conundrum. The phenotype of delayed puberty is associated with adult health risks and common etiologies, and there is evidence for polygenic control of pubertal timing in the general population, sex-specificity, and epigenetic modulation. Moreover, much has been learned from comprehension of monogenic and digenic etiologies of pubertal delay and associated disorders and, in recent years, knowledge of oligogenic inheritance in conditions of GnRH deficiency. Recently there have been several novel discoveries in the field of self-limited delayed puberty, encompassing exciting developments linking this condition to both GnRH neuronal biology and metabolism and body mass. These data together highlight the fascinating heterogeneity of disorders underlying this phenotype and point to areas of future research where impactful developments can be made.

Healthy Post-Menarchal Adolescent Girls Demonstrate Multi-Level Reproductive Axis Immaturity

Context

Menstrual irregularity after menarche has been attributed to immature estrogen positive feedback activity (E+FB) but data are conflicting.

Objective

To determine the hypothalamic-pituitary-ovarian contributions to menstrual irregularity in adolescents.

Methods

Twenty-three healthy girls [aged 12.8 to 17.6 years; 0.4 to 3.5 years postmenarche; body mass index (BMI) percentile, 41.0 to 99.3] underwent serial hormone measurements and pelvic ultrasounds during two consecutive menstrual cycles. Hormones and follicle growth were compared with 65 adult historic controls with ovulatory cycles (OVs).

Results

Girls had anovulatory cycles (ANOVs; 30%), OVs with a short luteal phase (short OVs; 22%), or OVs with normal luteal phase (normal OVs; 48%) without differences in cycle length, chronologic or gynecologic age, or BMI. Adolescents showed a spectrum of E+FB [midcycle LH adjusted for preovulatory estradiol (E2)]; only normal OV girls were comparable to adults. All OV girls had lower E2, progesterone, and gonadotropins during the luteal phase and luteal-follicular transition compared with adults. Normal OV girls also had lower follicular phase LH and FSH levels, a longer follicular phase, a slower dominant follicle growth rate, and smaller estimated preovulatory follicle size than adults. Follicular phase E2 and inhibin B levels were lower in normal OV girls than in adults even after adjusting for differences in FSH and follicle size.

Conclusions

Early postmenarchal girls with normal OVs demonstrate mature E+FB but continue to have lower gonadotropin levels, diminished ovarian responsiveness, and decreased corpus luteum sex steroid synthesis compared with adults, indicating that reproductive axis maturity requires coordinated development of all components of the hypothalamic-pituitary-ovarian axis.

Could long-term administration of melatonin to prepubertal children affect timing of puberty? A clinician's perspective

Exogenous melatonin can be used to treat sleep disturbance in adults, children, and adolescents. While its short-term use is considered safe, there are some concerns that long-term use might delay children's sexual maturation, possibly by disrupting the decline in nocturnal melatonin levels that occur at the onset of puberty. This narrative review aimed to summarize some of the current knowledge about the potential effects of exogenous melatonin on puberty. We found no clinical studies that experimentally tested the effects of melatonin on pubertal timing in children, but we reviewed the small number of observational studies. We also drew on animal data to try to answer our question. The photoperiod and melatonin-mediated seasonal transitions in sexual activity and breeding in some mammals across the seasons have been used as a model of sexual development in mammals, including humans. The switch from non-sexual activity (in the non-breeding period) to sexual activity (in the breeding period) has been likened to the onset of puberty as there are similarities between the two. We conclude that to investigate an association between melatonin and pubertal timing, it will be important to conduct long-term randomized controlled trials of latency age children and also examine the cellular and systems-level interactions between melatonin and kisspeptin, a recently identified neuropeptide with a locus of action at the gonadotropin releasing hormone neurons that is important in contributing to the timing of puberty onset.

High-sensitivity quantification of serum androstenedione, testosterone, dihydrotestosterone, estrone and estradiol by gas chromatography-tandem mass spectrometry with sex- and puberty-specific reference intervals

BACKGROUND

Androgen and estrogen determinations serve as important diagnostic markers in a variety of clinical conditions. However, one challenge is to enhance assay sensitivity for determination in the lowest range, such as in prepubertal children. We here present a recently developed gas chromatography-tandem mass spectrometry (GC-MS/MS) method for determination of androstenedione (A₄), dihydrotestosterone (DHT), testosterone (T), estrone (E₁), and estradiol (E₂) in children, which we have compared with the sensitive radioimmunoassays; E₂ extraction-RIA and T-RIA.

METHODS

Steroids were extracted in ethyl acetate n-hexane solution from serum spiked with isotopically labeled internal standard and derivatized sequentially with pentafluorobenzyl bromide, pentafluorobenzyl hydroxylamine and pentafluoropropionic acid anhydride and analyzed by GC-MS/MS using a triple quadrupole mass spectrometer operated in negative chemical ionization mode. Leftover routine samples (n = 414) were used to evaluate the concordance between GC-MS/MS and RIAs and the validity of GC-MS/MS for pediatrics; of these samples, 101 were from seemingly healthy children. Pubertal stage was recorded for reference interval evaluation.

RESULTS

Lower limit of detection for A₄, T, DHT, E₁, and E₂ were 0.1 nmol/L, 0.1 nmol/L, 27 pmol/L, 9 pmol/L, and 2 pmol/L, respectively. Good agreement was found between GC-MS/MS and T-RIA (r = 0.98) as well as between GC-MS/MS and E₂ extraction-RIA (r = 0.98, for E₂ concentrations above 14 pmol/L). In boys, T and DHT increased significantly from prepuberty throughout pubertal development, and in girls the same increase was observed for E₁ and E₂. The greatest increase in A₄ for both genders, as well as E₁ and E₂ in boys and T and DHT in girls, occurred in mid to late puberty.

CONCLUSIONS

We report the development of a GC-MS/MS method sensitive enough to accurately determine serum levels of androgens and estrogens in children.

Luteinizing Hormone Secretion during Gonadotropin-Releasing Hormone Stimulation Tests in Obese Girls with Central Precocious Puberty

OBJECTIVE

Girls with precocious puberty have high luteinizing hormone (LH) levels and advanced bone age. Obese children enter puberty at earlier ages than do non-obese children. We analyzed the effects of obesity on LH secretion during gonadotropin-releasing hormone (GnRH) tests in girls with precocious puberty.

METHODS

A total of 981 subjects with idiopathic precocious puberty who had undergone a GnRH stimulation testing between 2008 and 2014 were included in the study. Subjects were divided into three groups based on body mass index (BMI). Auxological data and gonadotropin levels after the GnRH stimulation test were compared.

RESULTS

In Tanner stage 2 girls, peak stimulated LH levels on GnRH test were 11.9±7.5, 10.4±6.4, and 9.1±6.1 IU/L among normal-weight, overweight, and obese subjects, respectively (p=0.035 for all comparisons). In Tanner stage 3 girls, peak stimulated LH levels were 14.9±10.9, 12.8±7.9, and 9.6±6.0 IU/L, respectively (p=0.022 for all comparisons). However, in Tanner stage 4 girls, peak stimulated LH levels were not significantly different among normal, overweight, and obese children. On multivariate analysis, BMI standard deviation score was significantly and negatively associated with peak LH (β=-1.178, p=0.001).

CONCLUSION

In girls with central precocious puberty, increased BMI was associated with slightly lower peak stimulated LH levels at early pubertal stages (Tanner stages 2 and 3). This association was not valid in Tanner stage 4 girls.

Control of the onset of puberty

PURPOSE OF REVIEW

The mechanism of puberty initiation remains an enigma, despite extensive research in the field. Pulsatile pituitary gonadotropin secretion under the guidance of hypothalamic gonadotropin-releasing hormone (GnRH) constitutes a sine qua non for pubertal onset. In turn, the secretion of GnRH in the human hypothalamus is regulated by kisspeptin and its receptor as well as by permissive or opposing signals mediated by neurokinin B and dynorphin acting on their respective receptors. These three supra-GnRH regulators compose the Kisspeptin, Neurokinin B and Dynorhin neurons (KNDy) system, a key player in pubertal onset and progression.

RECENT FINDINGS

The recent discovery that makorin ring finger protein 3 is also involved in puberty initiation provided further insights into the regulation of the KNDy pathway. In fact, the inhibitory (γ-amino butyric acid, neuropeptide Y, and RFamide-related peptide-3) and stimulatory signals (glutamate) acting upstream of KNDy called into question the role of makorin ring finger protein 3 as the gatekeeper of puberty. Meanwhile, the findings that 'neuroestradiol' produced locally and endocrine disruptors from the environment may influence GnRH secretion is intriguing. Finally, epigenetic mechanisms have been implicated in pubertal onset through recently discovered mechanisms.

SUMMARY

The exact molecular machinery underlying puberty initiation in humans is under intensive investigation. In this review, we summarize research evidence in the field, while emphasizing the areas of uncertainty and underlining the impact of current information on the evolving theory regarding this fascinating phenomenon.

Endocrine treatment of transsexual persons: an Endocrine Society clinical practice guideline

OBJECTIVE

The aim was to formulate practice guidelines for endocrine treatment of transsexual persons.

EVIDENCE

This evidence-based guideline was developed using the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) system to describe the strength of recommendations and the quality of evidence, which was low or very low.

CONSENSUS PROCESS

Committees and members of The Endocrine Society, European Society of Endocrinology, European Society for Paediatric Endocrinology, Lawson Wilkins Pediatric Endocrine Society, and World Professional Association for Transgender Health commented on preliminary drafts of these guidelines.

CONCLUSIONS

Transsexual persons seeking to develop the physical characteristics of the desired gender require a safe, effective hormone regimen that will 1) suppress endogenous hormone secretion determined by the person's genetic/biologic sex and 2) maintain sex hormone levels within the normal range for the person's desired gender. A mental health professional (MHP) must recommend endocrine treatment and participate in ongoing care throughout the endocrine transition and decision for surgical sex reassignment. The endocrinologist must confirm the diagnostic criteria the MHP used to make these recommendations. Because a diagnosis of transsexualism in a prepubertal child cannot be made with certainty, we do not recommend endocrine treatment of prepubertal children. We recommend treating transsexual adolescents (Tanner stage 2) by suppressing puberty with GnRH analogues until age 16 years old, after which cross-sex hormones may be given. We suggest suppressing endogenous sex hormones, maintaining physiologic levels of gender-appropriate sex hormones and monitoring for known risks in adult transsexual persons.

Accuracy of self-assessed Tanner staging against hormonal assessment of sexual maturation in overweight African-American children

AIM

To evaluate the accuracy of self-reported Tanner (SRT) staging against a proxy method of physician's assessment of sexual maturation, using pubertal hormones in overweight African-American (AA) children.

METHODS

Cross-sectional data from 196 children (113 girls, 83 boys) aged 9-11 years, who were 'overweight' (>85th and <95th percentile for age- and gender-matched BMI; n = 43) or 'obese' (>95th percentile; n = 153) were used. Children assessed their breast or genital and pubic hair development using standardized Tanner drawings representing different stages of sexual maturity. SRT data were compared to pubertal stage assessed by measuring fasting serum concentrations of luteinizing hormone (LH) in boys, and LH and estradiol (E2) in girls, which were used to stage children into pubertal stages 1-5.

RESULTS

SRT stages of genital and pubic hair assessments in boys, and breast and pubic hair assessments in girls, yielded 15-20% concordance (kappa statistic = 0.02-0.12) compared to their hormone-derived pubertal stages.

CONCLUSIONS

Among overweight AA 9-11 year-old children, self-assessment of Tanner staging did not accurately assess their pubertal development when compared to a hormone-derived pubertal assessment method.

Overnight luteinizing and follicle stimulating hormone profiles during GnRHa treatment in short girls born small for gestational age

BACKGROUND

Since puberty starting at a height less than 140 cm might reduce adult height, postponement of puberty was studied in short pubertal girls born SGA. Data on overnight LH and FSH profiles during GnRHa treatment are very limited.

AIMS

To evaluate whether 3 months of GnRHa treatment results in sufficient suppression of pubertal LH and FSH profile patterns. To evaluate whether girls show sufficient pubertal suppression according to a consensus-based peak LH cut-off level of 3 IU/l during a GnRH agonist test.

PARTICIPANTS

Twenty-one short pubertal girls born SGA.

INTERVENTION

After baseline LH and FSH profiles, children received leuprorelide acetate depots of 3.75 mg subcutaneously, every 4 weeks.

RESULTS

At baseline, amplitude and frequency of LH and FSH pulsatility were higher in girls with breast stage 3, compared to girls with breast stage 2. After 3 months of GnRHa treatment, all girls showed clinical arrest of puberty and their LH and FSH levels during overnight profiles had significantly decreased to prepubertal levels. In contrast, peak LH during the GnRH agonist test indicated insufficient pubertal suppression in 33% of girls. No differences in LH and FSH profiles were found between girls with a peak LH above or below 3 IU/l.

CONCLUSION

After 3 months of GnRHa treatment, central puberty was adequately suppressed in all girls, as shown by the prepubertal LH and FSH profiles. The GnRH agonist falsely indicated insufficient pubertal suppression in 33% of these girls.

Inducing puberty

Puberty is the result of increasing pulsatile secretion of the hypothalamic gonadotropin releasing hormone (GnRH), which stimulates the release of gonadotropins and in turn gonadal activity. In general in females, development of secondary sex characteristics due to the activity of the gonadal axis, i.e., the growth of breasts, is the result of exposure to estrogens, while in boys testicular growth is dependent on gonadotropins and virilization on androgens. Hypogonadotropic hypogonadism is a rare disease. More common is the clinical picture of delayed puberty, often associated with a delay of growth and more often familial occurring. Especially, boys are referred because of the delay of growth and puberty. A short course (3-6 months) of androgens may help these boys to overcome the psychosocial repercussions, and during this period an increase in the velocity of height growth and some virilization will occur. Hypogonadotropic hypogonadism may present in a congenital form caused by developmental disorders, some of which are related to a genetic disorder, or secondary to hypothalamic-pituitary dysfunction due to, among others, a cerebral tumor. In hypogonadotropic hypogonadism puberty can be initiated by the use of pulsatile GnRH, gonadotropins, and sex steroids. Sex steroids will induce development of the secondary sex characteristics alone, while combined administration of gonadotropins and GnRH may induce gonadal development including fertility.

Pubertal development in children and adolescents born after IVF and spontaneous conception

BACKGROUND

Previous studies demonstrated a link between adverse conditions during prenatal life and the development of diseases in adult life. It is still unclear whether IVF conception could permanently affect early prenatal development in humans, with post-natal health consequences. The objective of the present study is to examine pubertal development in 8-18-year-old IVF singletons and controls born from subfertile parents who attended one Dutch fertility clinic were included.

METHODS

IVF singletons and controls born from subfertile parents who attended one clinic in the Dutch OMEGA study were included. Pubertal stage by Tanner's classification, age at menarche and menstrual cycle characteristics were studied in the total population (n = 233: 115 IVF-conceived boys and 118 IVF-conceived girls, each with age-matched comparison groups). Bone age and sex hormone levels were examined in two distinct pubertal subpopulations.

RESULTS

Pubertal stage and age at menarche were not significantly different between IVF and control children. In the pubertal subpopulation, a higher bone age-chronological age (BA-CA) ratio and a larger BA-CA difference were observed in IVF-conceived girls compared with controls (1.04 +/- 0.07 versus 1.02 +/- 0.08, P = 0.022; 0.54 +/- 0.82 versus 0.18 +/- 1.00 year, P = 0.021, respectively). Furthermore, dehydroepiandrosterone sulphate (DHEAS) and LH levels were significantly higher in IVF-conceived girls than in control subjects (2.5 versus 1.9 micromol/l, P = 0.017, and 1.5 versus 0.6 U/l, P = 0.031, respectively).

CONCLUSIONS

Bone age appeared to be advanced in pubertal IVF-conceived girls, but not in boys, compared with controls. Increased DHEAS and LH concentrations were found among IVF girls.

Could bone tissue be a target for luteinizing hormone/chorionic gonadotropin?

Ovariectomy (OVX) and Zoladex administration to adult rats gave conflicting results with respect to the excretion of total urinary hydroxyproline (OH-Pro), a valuable indicator of bone collagen catabolism. Whereas OVX culminated in early (1 week) increases in OH-Pro, the use of Zoladex actually lowered OH-Pro and showed no sign of increasing over controls for a 2-month period. Since both OVX and Zoladex produce a state of estrogen deficiency we reasoned that the differential effects of the two procedures on OH-Pro were attributed to LH status. Receptors for luteinizing hormone (LH)/human chorionic gonadotropin (hCG) have been identified in many, non-gonadal, estrogen sensitive sites and although bone is receptive to estrogen what effects LH/hCG might have upon bone metabolism have received scant attention. Treatment of osteoblasts in culture with a urinary derived formulation of hCG resulted in increased alkaline phosphatase (ALP) activity, raised matrix mettaloproteinase-2 (MMP-2) levels and increased expression of type I collagen. Further studies, using murine calvaria, supported a bone-resorbing effect of hCG. Taken together our initial findings suggested that raised hCG and/or LH might lead to an overall increase in bone matrix turnover as reported for puberty, pregnancy and the menopause. However, when the urinary derived preparation of hCG was replaced with recombinant hormone no changes in osteoblast activity were found implying the presence of contaminating agents in the urine derived hCG. Herein we describe that epidermal growth factor (EGF) could account for the changes observed for urinary derived hCG in osteoblast cultures and that the effects of LH/hCG on bone tissue are probably indirect.

Premature adrenarche, polycystic ovary syndrome and intrauterine growth retardation: does a relationship exist?

PURPOSE OF REVIEW

Describes the origin of premature adrenarche and polycystic ovary syndrome.

RECENT FINDINGS

Growing evidence has emerged on the relationship between intrauterine growth retardation, premature adrenarche and polycystic ovary syndrome.

SUMMARY

Experimental animal research and clinical observations underline the early developmental origin of premature adrenarche and polycystic ovary syndrome. Polycystic ovaries have been noted in girls before the onset of puberty which supports the suggestion that the origin of the syndrome depends on programming of the ovary in utero. Androgens during fetal life may initially be responsible for the programming of the ovary eventually leading to polycystic ovary syndrome. In addition, the development of the syndrome is proposed to be a linear process as a result of programming of the adrenal whereby hyperandrogenaemia starting in utero, during childhood and thereafter, plays a prominent role. At the beginning of puberty androgens produced by the adrenal initiate a vicious circle characterized by neuroendocrine abnormalities partly related to androgen-dependent decreases in gonadotropin-releasing hormone pulse generator sensitivity to the negative feedback actions of ovarian steroids. This promotes the progression towards the adult polycystic ovary syndrome phenotype.

Puberty and depression

Unipolar depression only becomes more common in girls than boys after the age of 13, as a result of an increased incidence of depressive episodes in girls at that time. This article reviews evidence that links multiple dimensions of maturation in the hypothalamo-pituitary-gonadal axis with this phenomenon. Effects of developmental status and timing have been implicated, but few studies have deployed either the measurement strategies or the statistical power needed to provide a satisfactory answer to the question regarding which components of puberty are most responsible.

The origins and sequelae of abnormal neuroendocrine function in polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is a common clinical disorder characterized by ovulatory dysfunction and hyperandrogenaemia. A neuroendocrine hallmark of PCOS is persistently rapid LH (GnRH) pulsatility, which favours pituitary synthesis of LH over that of FSH and contributes to the increased LH concentrations and LH : FSH ratios typical of PCOS. Inadequate FSH levels contribute to impaired follicular development, whereas elevated LH levels augment ovarian androgen production. Whereas luteal phase elevations in progesterone normally slow GnRH pulse frequency, women with PCOS do not experience normal progesterone-mediated slowing, due in part to impaired hypothalamic progesterone sensitivity. This reduction in hypothalamic progesterone sensitivity appears to be mediated by elevated androgens because sensitivity can be restored with the androgen receptor blocker flutamide. The ovulatory and hormonal abnormalities associated with PCOS generally present during puberty, typically associated with hyperandrogenaemia. Along with elevated LH concentration and pulsatility, some girls with hyperandrogenaemia have impaired hypothalamic progesterone sensitivity similar to that seen in adult women with PCOS. We propose that peripubertal hyperandrogenaemia may lead to persistently rapid GnRH pulse frequency via impaired hypothalamic feedback inhibition. The subsequent abnormalities in gonadotropin secretion, androgen production and ovulatory function may support progression towards the adult PCOS phenotype.

EGF-like factor epiregulin and amphiregulin expression is regulated by gonadotropins/cAMP in human ovarian follicular cells

Epiregulin and amphiregulin are growth factors involved in cancer development, but their potential role in signaling in the gonads is still obscure. We report here that basal expression of these growth factors is evident in human granulosa cells obtained from women treated for in vitro fertilization, when examined by RT-PCR using RNA isolated from primary cultures of ovarian granulosa cells. Expression of these factors was elevated concomitantly with elevation of progesterone production in these cells upon stimulation with luteinizing hormone (LH), and to a lesser extent with follicle stimulating hormone (FSH), both essential stimulants for ovulation and luteinization. Epiregulin and amphiregulin gene expression was dose- and time-dependent when measured subsequent to LH stimulation. Moreover, forskolin, which activates adenylate cyclase, was as efficient as LH in stimulating expression of these growth factors. It is suggested that upregulation of the epiregulin and amphiregulin expression is part of the signal transduction pathway which leads to ovulation and luteinization in the human ovary.

Luteinizing hormone receptor knockout (LuRKO) mice and transgenic human chorionic gonadotropin (hCG)-overexpressing mice (hCG alphabeta+) have bone phenotypes

Considerable attention has been paid to the role of sex steroids during periods of major skeletal turnover, but the interaction of the gonadotropic hormones, which include LH, FSH, and human chorionic gonadotropin (hCG), within bone tissue have been overlooked. The question is pertinent due to the recent detection of extragonadal expression of gonadotropin receptors. Western blotting, immunolocalization, and RT-PCR supported the presence of osteoblast LH receptors. However, osteoblast cells failed to bind [(125)I]hCG and treatment with hCG failed to generate either cAMP or phosphorylated ERK 1/2. Bone mineral density (BMD) and bone histomorphometry were examined in the following models: 1) LH receptor null mutant (LuRKO) mice; 2) transgenic mice overexpressing hCG (hCG alphabeta+); and 3) ovariectomized (OVX) hCG alphabeta+ model. Male LuRKO mice showed a decrease in BMD after 5 months, apparently secondary to suppressed gonadal steroid production. Similarly, 9- to 10-wk-old female LuRKO mice exhibited decreases in histomorphometric parameters tested. The data indicate that loss of LH signaling results in a reduction in bone formation or an increase in bone resorption. By contrast, there were significant increases in BMD and histomorphometric indices for female, but not male, hCG alphabeta+ mice, indicating that chronic exposure to hCG results in bone formation or a decrease in bone resorption. However, OVX of the hCG alphabeta+ mice resulted in a significant reduction in BMD comparable to OVX WT controls. Although gonadotropin levels are tightly linked to sex steroid titers, it appears that their effects on the skeleton are indirect.

Regulation of puberty

Pubertal development is the last phase of a continuum of changing gonadotrophin releasing hormone (GnRH) activities. Whether or not puberty tends to start at a younger age, as has been recently described in a population of black Americans, remains under debate. Such early onset has not been confirmed in different European countries. Ideas about the underlying mechanisms responsible for the reawakening of GnRH release at the onset of puberty have changed significantly during the last decades. At this moment, the common opinion is that neuronal outgrowth of both GnRH and other regulatory neurons results in changing interactions and activities. Sex steroids, as well as various central neurotransmitters, play a role in modulating GnRH release. Active release after birth is followed by the restraint of childhood. A re-onset of GnRH excitatory activities heralds the onset of puberty. This chapter gives an overview of the many factors involved.

Neurobiological mechanisms of the onset of puberty in primates

An increase in pulsatile release of LHRH is essential for the onset of puberty. However, the mechanism controlling the pubertal increase in LHRH release is still unclear. In primates the LHRH neurosecretory system is already active during the neonatal period but subsequently enters a dormant state in the juvenile/prepubertal period. Neither gonadal steroid hormones nor the absence of facilitatory neuronal inputs to LHRH neurons is responsible for the low levels of LHRH release before the onset of puberty in primates. Recent studies suggest that during the prepubertal period an inhibitory neuronal system suppresses LHRH release and that during the subsequent maturation of the hypothalamus this prepubertal inhibition is removed, allowing the adult pattern of pulsatile LHRH release. In fact, y-aminobutyric acid (GABA) appears to be an inhibitory neurotransmitter responsible for restricting LHRH release before the onset of puberty in female rhesus monkeys. In addition, it appears that the reduction in tonic GABA inhibition allows an increase in the release of glutamate as well as other neurotransmitters, which contributes to the increase in pubertal LHRH release. In this review, developmental changes in several neurotransmitter systems controlling pulsatile LHRH release are extensively reviewed.

GH substitution does not alter the pulsatile pattern of LH in amenorrhoeic growth hormone deficient women

OBJECTIVE

GH substitution in GH-deficient (GHD) children promotes pubertal development. In some GHD women, secondary amenorrhoea occurs after discontinuation of GH treatment. This study was designed to investigate whether GH substitution directly influences the GnRH pulse generator. For this reason, the pulsatile release of LH was studied in amenorrhoeic GHD women before and during GH substitution.

DESIGN

GH deficiency was confirmed by an insulin tolerance test. During a 24-h period, blood samples were drawn every 10 min for determination of LH, FSH and GH levels. Oestradiol and IGF-1 were determined at 1000 h and 2200 h. After the first test day, patients started with GH substitution, 0.25 IU/kg/week. During month 6 of GH treatment, the 24 h blood sampling was repeated.

SUBJECTS

Ten amenorrhoeic GH-deficient women participated in the trial. All were diagnosed as GH deficient during childhood or adolescence. Eight of them had been treated with GH during childhood. Seven women suffered from primary amenorrhoea and three from secondary amenorrhoea. Six women were started with GH substitution after the first test day (according to randomization in a larger study).

MEASUREMENTS

LH and GH were determined every 10 min and FSH every 60 min. LH pulse detection was conducted using a validated statistical method.

RESULTS

Prior to GH treatment, the LH pulse interval did not show a diurnal pattern as found during normal pubertal development. During GH treatment, IGF-1 levels rose significantly. No differences were found in mean LH, LH pulse amplitude and LH pulse interval before and during GH treatment. Oestradiol levels did not change either.

CONCLUSIONS

GH substitution in amenorrhoeic GH-deficient women does not alter the pulsatile pattern of LH. This may suggest that GH treatment does not influence central nervous system control of gonadotropin secretion in GHD patients.

The endocrinology of dizygotic twinning in the human

Heredity, higher maternal age and increased parity are well defined conditions associated with dizygotic twinning. An endocrine model of excessive secretion of pituitary gonadotrophic hormones explains multiple ovulation as a result of multiple follicle growth. In hereditary conditions FSH levels are indeed clearly elevated because of increase in stimulating mechanisms that regulate pituitary gonadotropin secretion while in most non-hereditary conditions, overshoot FSH secretions occurs as a result of diminished ovarian feedback. Puberty is a condition in which the hypothalamic LHRH pulse generator is reinitiated and this is typically characterized by temporary overshoot LH and FSH secretion, probably due to not yet fully operational ovarian feedback. In adult females situations can be found that mimic this peripubertal event such as while recovering from hypothalamic amenorrhea. Under these circumstances more DZ twinning can be observed. Elevated FSH levels along with ageing in premenopausal women probably underlie the age related increased risk of dizygotic twinning. The apparent paradox in the combination of age related decline in fecundity and rise in twinning risk can be explained by incidental presence in the cohort of more than one follicle, containing vital oocytes under deficient feedback mechanisms that lead to high FSH.

Interpretation of elevated FSH in the regular menstrual cycle

In reproductive medicine, abnormal elevation of serum follicle stimulating hormone (FSH) concentrations during the luteofollicular transition is associated with low response in infertility treatment. Increasing levels of serum FSH in the early follicular phase is a characteristic of reproductive ageing and has become very popular for the determination of diminished ovarian oocyte reserve. In the case of elevated FSH in premenopausal women, many more (patho)physiological mechanisms other than ageing may be responsible and should be considered also. FSH concentrations may vary considerably due to a number of factors. Next to intra-, inter- and between different assays variation there is hourly-, cycle day dependent-, intercycle and life time variation. Furthermore, physiological conditions such as during puberty, in hereditary dizygotic twinning, after use of oral contraceptives and during lactation also elevated FSH levels can be found. Pathological conditions associated with significant increases in FSH are after unilateral ovariectomy, during recovery from hypothalamic amenorrhea and with excessive smoking. It should be kept in mind, that with the interpretation of an abnormal high FSH value, just as with any other abnormal laboratory results, one should be aware, that there may be a variety of underlying causes other than the one where was aimed at.

Gonadotrophin pulsatility in girls with the Turner syndrome: modulation by exogenous sex steroids

OBJECTIVES

The endocrine manifestation of puberty, nocturnal pulsatile secretion of gonadotrophins precedes the physical manifestations by 2 years. Whether gonadal steroids and inhibin have a role to play in the regulation of pulsatile gonadotrophin release is unclear. The agonadal model, girls with Turner's syndrome (TS), has been used to determine the role of the hypothalamic pulse generator in the ontogeny of gonadotrophin secretion in man. We evaluated the ontogeny of gonadotrophin secretion in TS girls with respect to amplitude and frequency and compared these results to those obtained in a group of normal girls. The effects of treatment with ethinyloestradiol (EE2) or oxandrolone (OX) on parameters of gonadotrophin secretion were also evaluated.

PATIENTS

We studied 32 girls with TS, aged 4.3-12.4 years. All were prepubertal at the start of the study and longterm follow up revealed that none entered spontaneous puberty. The pulse amplitude and frequency was evaluated and compared to the results obtained in 23 normal girls, aged 4.9-12.8 years who acted as controls.

MEASUREMENTS

Samples were taken at 20 minute intervals for 24 h for the measurement of serum concentrations of luteinising (LH) and follicle stimulating (FSH) hormones. The girls were than randomized to receive EE2 or OX and were then re-admitted 6 months into the course of the treatment for a repeat 24 h serum profile of LH and FSH levels.

RESULTS

The girls with TS showed a clearly defined dominant pulse periodicity of 180 min and that in the normal cohort was 160-220 min. The girls with TS had an increased oscillatory activity between 120 and 260 min compared to the normal. Mean 24 h serum gonadotrophin concentration in TS girls was always higher than in the normal cohort. The inflection points of the fitted polynomial regression equation relating sex hormone concentration with age was similar for the two groups. EE2 lead to a significant change in pulse periodicity in TS girls but OX had no significant effect on the pulse periodicity.

CONCLUSION

These results demonstrate that girls with Turner syndrome have gonadotrophin pulse periodicity in the prepubertal years similar to those of normal girls. The oscillatory activity was much greater in girls with Turner syndrome at all ages in the prepubertal years, suggesting a role for the ovary in modulating gonadotrophin secretion in the prepubertal years. Our data confirm that in girls with Turner syndrome the normal pattern of gonadotrophin secretion evolving with time is preserved.

Hypothetical risks of twinning in the natural menstrual cycle

Dizygotic (DZ) twinning is likely the result of multiple ovulation upon multiple ongoing follicle growth. Well known conditions with an increased incidence of DZ twinning are a hereditary trait, high maternal age and ovulation induction treatments. These conditions are clearly related to elevation of Follicle Stimulating Hormone (FSH) at the time of peri-menstrual follicle recruitment. In this contribution, we summarize certain other circumstances that may occur in normal women that could increase twinning rate based on the assumption that the elevation of FSH levels is the principal underlying mechanism in DZ twinning. It is hypothesized that recovery from prolonged hypothalamic amenorrhea in part mimics hormonal sequelae of puberty characterized by temporary overshoot of FSH levels. By deduction, such conditions are recovery from lactational amenorrhea, recovery from use of oral contraceptives and recovery of weight loss amenorrhea. According to the literature, these conditions indeed carry the risk of DZ twinning and all show temporary elevated FSH levels. However, prospective experiments will be needed to prove the relation between this type of DZ twinning and possible patterns of serum FSH that mimic puberty under these circumstances.

Development of the hypothalamic-pituitary-ovarian axis

The onset of puberty is a centrally driven process, the detailed mechanisms of which are not known. It is translated into an increased activity of the hypothalamic GnRH pulse generator. This in turn is seen as increased pituitary pulsatile secretion of LH and FSH. LH pulses are observed even in midchildhood, particularly after the onset of sleep. Onset of puberty is associated with a greater increase in LH pulse amplitude than frequency and a much greater increase in LH and FSH. A progressive increase in daytime pulsatility occurs, with a gradual reduction of sleep-entrained amplification. Prepubertal FSH concentrations are relatively high in girls, and continous ovarian follicular growth and atresia take place, with estradiol concentrations being higher than in boys. Only after the steep early pubertal increase in LH, ovarian steroidogenesis is activated, with increases in androgen and estrogen secretion. Under further FSH stimulation, follicular growth and maturation proceed. The first menstrual cycles are mostly anovulatory for 1 to 2 years. Luteal phase insufficiency is common the first five years after menarche.

Anovulation and monophasic cycles

Normal pubertal development is often considered complete when the adolescent experiences her first menstrual period. However, sexual maturity is not attained until the onset of regular ovulatory cycles, which may take a number of months to years to accomplish. This maturation process is orchestrated by a neuroendocrine cascade and modified by autocrine and paracrine events in the ovary. The control of these complex relationships takes time and could not be expected to be fully functional with menarche. During the first menstrual months, the hypothalamic-pituitary-ovarian axis is immature, resulting in the secretion of only estrogens from the developing follicles; positive feedback to trigger ovulation develops later. Consequently, estrogen secretion is variable and unopposed by progesterone, which would normally be produced in ovulatory cycles. Estrogen-only primed endometrium often leads to irregular menstrual cycles with variable flow. Surprisingly, most adolescents do well and have few complaints in spite of these anovulatory cycles. If an abnormality is experienced with the menstrual cycle, once understood physiologically, it can be managed simply, by watchful expectancy or intermittent progestin therapy. Occasionally, sever menstrual bleeding is encountered, and in a proportion of these patients a thorough assessment will delineate an underlying medical problem that needs to be addressed. The management of these patients requires ingenuity from the pediatric reproductive endocrinologist and aggressive hormonal manipulation. Most patients do well, but some require long-term continuing care.

Monthly urinary gonadotropin and ovarian hormone excretory patterns in normal girls and female patients with idiopathic precocious puberty

To identify the developmental changes in monthly urinary gonadotropin and ovarian hormone excretion, consecutive 30-d first morning void urinary specimens were collected from 36 normal girls, one normal woman, and 15 female patients with idiopathic precocious puberty. Of these children, three normal girls and three patients with precocious puberty volunteered to collect these specimens on 2-3 occasions over a time interval of 0.5-3.2 y. When sampled, six were early prepubertal, nine late prepubertal, eight early pubertal, eight mid-pubertal, and eight late pubertal normal girls, and six were early pubertal and 14 mid-pubertal patients with precocious puberty. The mean level of monthly urinary LH, FSH, and total estrogen excretions increased with pubertal maturation. In prepuberty, the mean LH level was lower than the mean FSH level, and neither showed significant episodic fluctuations. In early puberty, mean FSH levels increased with remarkable fluctuations, and mean LH levels were low with few variations in the course of a month. At the onset of puberty, gonadotropin excretory patterns underwent specific changes, showing at the same time periodically and every other day fluctuating patterns. Urinary total estrogen and pregnanediol excretion fluctuated independently from these periodic variations in urinary gonadotropins. These patterns were observed in six out of 16 patterns in normal pubertal girls and 10 out of 20 patterns in precocious puberty. Once the urine LH level exceeded the urine FSH level, however, these periodic variations disappeared. The cycle of a normal postmenarcheal girl aged 14 y showed a pattern similar to that of a normal adult. In patients with precocious puberty, the hormonal patterns were similar to those of sexual stage-matched normal girls.

Melatonin and gonadotropin secretion after acute exercise in physically active males

Serum concentrations of luteinizing hormone (LH), follicle stimulating hormone, testosterone (T) and melatonin were measured in seven physically active male volunteers after exercise on a treadmill using the Bruce protocol. Measurements were made on blood samples obtained before exercise, within 30 s after exercise, at 15 min after exercise, and subsequently at 30-min intervals after exercise for a total duration of 180 min. Serum LH concentration fell from a peak post-exercise level of 15.7 (4.7) IU.l-1 [mean (SD)] to a nadir of 10.3 (2.4) IU.l-1 (P < 0.004). Nadir values in individual volunteers were seen between 60 and 150 min after exercise. This fall in serum LH was paralleled by a similar fall in the concentration of serum T. Serum melatonin concentrations did not change significantly after exercise. It is concluded that melatonin, despite is reported anti-gonadotropic properties, does not play a role in the depression of serum LH after acute strenuous exercise in physically active males.