Assessment of circulating sex steroid levels in prepubertal and pubertal boys and girls by a novel ultrasensitive gas chromatography-tandem mass spectrometry method

Influence of the X-chromosome on neuroanatomy: evidence from Turner and Klinefelter syndromes

Studies of sex effects on neurodevelopment have traditionally focused on animal models investigating hormonal influences on brain anatomy. However, more recent evidence suggests that sex chromosomes may also have direct upstream effects that act independently of hormones. Sex chromosome aneuploidies provide ideal models to examine this framework in humans, including Turner syndrome (TS), where females are missing one X-chromosome (45X), and Klinefelter syndrome (KS), where males have an additional X-chromosome (47XXY). As these disorders essentially represent copy number variants of the sex chromosomes, investigation of brain structure across these disorders allows us to determine whether sex chromosome gene dosage effects exist. We used voxel-based morphometry to investigate this hypothesis in a large sample of children in early puberty, to compare regional gray matter volumes among individuals with one (45X), two (typically developing 46XX females and 46XY males), and three (47XXY) sex chromosomes. Between-group contrasts of TS and KS groups relative to respective sex-matched controls demonstrated highly convergent patterns of volumetric differences with the presence of an additional sex chromosome being associated with relatively decreased parieto-occipital gray matter volume and relatively increased temporo-insular gray matter volumes. Furthermore, z-score map comparisons between TS and KS cohorts also suggested that this effect occurs in a linear dose-dependent fashion. We infer that sex chromosome gene expression directly influences brain structure in children during early stages of puberty, extending our understanding of genotype-phenotype mechanisms underlying sex differences in the brain.

17-Hydroxyprogesterone in children, adolescents and adults

17-Hydroxyprogesterone (17-OHP) is an intermediate steroid in the adrenal biosynthetic pathway from cholesterol to cortisol and is the substrate for steroid 21-hydroxylase. An inherited deficiency of 21-hydroxylase leads to greatly increased serum concentrations of 17-OHP, while the absence of cortisol synthesis causes an increase in adrenocorticotrophic hormone. The classical congenital adrenal hyperplasia (CAH) presents usually with virilisation of a girl at birth. Affected boys and girls can have renal salt loss within a few days if aldosterone production is also compromised. Diagnosis can be delayed in boys. A non-classical form of congenital adrenal hyperplasia (NC-CAH) presents later in life usually with androgen excess. Moderately raised or normal 17-OHP concentrations can be seen basally but, if normal and clinical suspicion is high, an ACTH stimulation test will show 17-OHP concentrations (typically >30 nmol/L) above the normal response. NC-CAH is more likely to be detected clinically in females and may be asymptomatic particularly in males until families are investigated. The prevalence of NC-CAH in women with androgen excess can be up to 9% according to ethnic background and genotype. Mutations in the 21-hydroxylase genes in NC-CAH can be found that have less deleterious effects on enzyme activity. Other less-common defects in enzymes of cortisol synthesis can be associated with moderately elevated 17-OHP. Precocious puberty, acne, hirsutism and subfertility are the commonest features of hyperandrogenism. 17-OHP is a diagnostic marker for CAH but opinions differ on the role of 17OHP or androstenedione in monitoring treatment with renin in the salt losing form. This review considers the utility of 17-OHP measurements in children, adolescents and adults.

Pubertal growth and serum testosterone and estradiol levels in boys

BACKGROUND/AIMS

To study serum testosterone and estradiol in healthy boys in relation to growth during puberty up to peak height velocity (PHV).

METHODS

Growth velocity was analyzed through testosterone (n = 41) and 17β-estradiol (n = 37) 24-hour profiles in a dose-response model. Participants were 26 healthy boys admitted for short or tall stature or participating as healthy volunteers at the Queen Silvia Children's Hospital. Other inclusion criteria included the following: gestational age 37-42 weeks, birth weight and length >-2 standard deviation score (SDS) and prepubertal height and weight within ± 3 SDS. Testosterone was measured using a modified radioimmunoassay (RIA) with a detection limit of 0.03 nmol/l. Estradiol was determined using an ultrasensitive extraction RIA with a detection limit 4 pmol/l. A sixth-grade polynomial was fitted to each child's growth data, giving growth velocity and age at PHV.

RESULTS

Growth velocity increased by 50% from prepubertal growth to PHV at a morning testosterone level of 3.1 nmol/l (95% confidence interval 2.4-4.2), EC50. The corresponding EC50 of 17β-estradiol was 6.5 pmol/l (3.2-13). Boys approaching PHV (<4% remaining) had morning testosterone levels >10 nmol/l and 17β-estradiol >9 pmol/l.

CONCLUSION

Observed early puberty/initial mid puberty morning testosterone levels of 2.4-4.2 nmol/l are associated with a 50% increase in growth velocity from prepubertal growth to PHV in healthy boys.

Androgens and stroke: good, bad or indifferent?

Cerebral ischemia caused by loss of blood supply to the brain during cardiac arrest or stroke are major causes of death and disability. Biological sex is an important factor in predicting vulnerability of the brain to an ischemic insult, with males being at higher risk for cardio-cerebrovascular events than females of the same age. However, relative incidence of stroke between the genders appears to normalize at advanced ages. Therefore, many scientists have focused on the mechanisms of sex differences in outcome following brain ischemic injury, with a particular emphasis on the role of sex steroids. The majority of studies indicate that female sex steroids, such as estrogen and progesterone, play important roles in the relative neuroprotection following cerebral ischemia observed in females. However, less is known about male sex steroids and brain damage. This review describes the state of our knowledge of androgen-related contributions to neurological injury and recovery following cerebral ischemia that occurs following stroke. Experimental studies examining the effects of castration, androgenic agonists and antagonists and aging provide valuable insights into the role of androgens in clinical outcome following cerebrovascular events.

Identification and quantification of 5α-dihydrotestosterone in the teleost fathead minnow (Pimephales promelas) by gas chromatography-tandem mass spectrometry

The steroid hormone 5α-dihydrotestosterone (DHT) is one of the most physiologically important androgens in male vertebrates, with the exception of teleost fish, in which it is generally assumed that DHT does not play any major physiological role. However, this assumption is challenged by the fact that all the components involved in DHT biosynthesis and action are present and evolutionary conserved in teleost fish. In fact, testosterone (T) is converted into DHT by two isoforms of the enzyme steroid-5-alpha-reductase (5αR), and both 5αRs gene expression and enzymatic activity have been detected in several tissues of different teleost species, which also have an androgen receptor with high binding affinity to DHT. This body of evidence strongly suggest that DHT is synthesised by teleost fish. We investigated this hypothesis using the cyprinid fathead minnow (Pimephales promelas) as the experimental model. The study of the evolutionary and functional conservation of 5αRs in teleost fish was used to support the experimental approach, based on an ultrasensitive gas chromatography-tandem mass spectrometry (GC-MS/MS) method to identify and measure simultaneously T and DHT in fathead minnow biological fluids and tissues. The analyses were performed using plasma samples collected from both male and female adult fish and samples of testicular tissue collected from sexually mature males. Both T and DHT were identified and quantified in all the samples analysed, and in particular, the high concentrations of DHT quantified in the testes suggested that these organs are a likely site of synthesis of DHT in the teleost fathead minnow, as they are in mammals. These results may represent the basis for future studies aimed at elucidating the physiological role, if any, of DHT in teleost fish.

Exogenous pubertal induction by oral versus transdermal estrogen therapy

Hypogonadal adolescent girls need estrogen therapy for the induction of puberty. For years, oral conjugated estrogens have been used for this purpose, starting at a very low dose, with gradual increments over time, to allow for the maturation of the reproductive organs, in order to mimic physiologic conditions. Several concerns, mainly due to first pass through the liver, are manifest with oral estrogen therapy. With the advent of transdermal estrogens and its improved efficacy profile as well as reduced side effects, it seems reasonable to consider it for pubertal induction. The primary objective of this study was to compare and contrast oral versus transdermal estrogen with regard to metabolism and physiology and to review current available data on transdermal estrogens with respect to exogenous pubertal induction.

Simultaneous determination of endogenous steroid hormones in human and animal plasma and serum by liquid or gas chromatography coupled to tandem mass spectrometry

Analytical methodologies based on liquid or gas chromatography coupled to tandem mass spectrometry for the simultaneous determination of two or more endogenous steroid hormones in human and animal plasma and serum has received increased attention the last few years. Especially in the clinical setting steroid profiling is of major importance in disease diagnostics. This paper discusses recent findings in such multi-steroid hormone procedures published from 2001 to 2012. The aim was to elucidate possible relationships between chosen analytical technique and the obtained analyte sensitivity for endogenous steroid hormones. By evaluating the success, at which the currently applied techniques have been utilized, more general knowledge on the field is provided. Furthermore the evaluation provides directions in which future studies may be interesting to conduct.

Alcohol exposure during late adolescence increases drinking in adult Wistar rats, an effect that is not reduced by finasteride

AIMS

We tested whether an exposure to alcohol in late adolescence, an age of rapid increase in neuroactive steroid precursors, would increase voluntary alcohol consumption in adult rats and whether this effect would be modulated by finasteride, an inhibitor of neuroactive steroid synthesis.

METHODS

In Experiment 1, we exposed male Wistar rats to 8% alcohol during the dark cycle for 1 week during late adolescence [postnatal days (PNDs) 51-58], and then measured voluntary alcohol consumption 1 month later in adulthood (PNDs 91-104). In Experiment 2, finasteride was administered during the forced alcohol exposure in late adolescence and, in Experiment 3, during voluntary alcohol consumption in adulthood. Plasma was collected at the end of each finasteride treatment to confirm the reduction of plasma neuroactive steroid levels.

RESULTS

We found that a daily 12-h exposure to alcohol for 7 days in late adolescence significantly increased voluntary alcohol consumption (4-fold) a month later during adulthood. Finasteride administration in late adolescence increased group alcohol intake in late adolescence but did not block the effect of adolescent alcohol exposure on increasing alcohol preference in adulthood. There was no effect of finasteride treatment in adulthood on alcohol preference.

CONCLUSIONS

A daily 12-h exposure to alcohol for 7 days in late adolescence was sufficient to induce chronically increased alcohol preference in adulthood, indicating that this age may be sensitive to the effects of alcohol.

Tandem mass spectrometry in hormone measurement

Mass spectrometry methods have the potential to measure different hormones during the same analysis and have improved specificity and a wide analytical range compared with many immunoassay methods. Increasingly in clinical laboratories liquid chromatography-tandem mass spectrometry (LC-MS/MS) assays are replacing immunoassays for the routine measurement of testosterone, 17-hydroxyprogesterone, and other steroid hormones. Reference LC-MS/MS methods for steroid, thyroid, and peptide hormones are being used for assessment of the performance and calibration of commercial immunoassays. In this chapter, the general principles of tandem mass spectrometry and examples of hormone assays are described.

A plausible explanation for male dominance in typhoid ileal perforation

The phenomenon of consistent male dominance in typhoid ileal perforation (TIP) is not well understood. It cannot be explained on the basis of microbial virulence, Peyer’s patch anatomy, ileal wall thickness, gastric acidity, host genetic factors, or sex-linked bias in hospital attendance. The cytokine response to an intestinal infection in males is predominantly proinflammatory as compared with that in females, presumably due to differences in the sex hormonal milieu. Sex hormone receptors have been detected on lymphocytes and macrophages, including on Peyer’s patches, inflammation of which (probably similar to the Shwartzman reaction/Koch phenomenon) is the forerunner of TIP, and is not excluded from the regulatory effects of sex hormones. Hormonal control of host-pathogen interaction may override genetic control. Environmental exposure to Salmonella typhi may be more frequent in males, presumably due to sex-linked differences in hygiene practices and dining-out behavior. A plausible explanation of male dominance in TIP could include sex-linked differences in the degree of natural exposure of Peyer’s patches to S. typhi. An alternative explanation may include sexual dimorphism in host inflammatory response patterns in Peyer’s patches that have been induced by S. typhi. Both hypotheses are testable.

The physiology and timing of male puberty

PURPOSE OF REVIEW

To describe available markers of male puberty, discuss associations between adiposity and pubertal timing and to review recent evidence of a possible secular trend in male pubertal timing.

RECENT FINDINGS

An expert panel reviewing existing American pubertal data from boys in 2005 could not confirm a secular trend in male pubertal timing. National Health and Nutrition Examination Survey III findings have been confirmed by the National Institute of Child Health and Human Development study reporting a mean age of 10.4 years for Caucasian boys entering Tanner stage G2. Furthermore, the Copenhagen Puberty Study reported a 3 months decline in pubertal onset during a 15-year period (from 11.92 years in 1991 to 11.66 years in 2008).A negative association between obesity and early puberty was found in the National Institute of Child Health and Human Development study, in contrast to the positive association found in a Danish study. Other studies have not been able to document an association between prepubertal BMI and age at pubertal onset.

SUMMARY

Evaluation of Tanner stage and especially assessment of testicular volume should both be used in epidemiological studies. We speculate that the association between fat mass and pubertal timing may be nonlinear and recent studies may indicate a small decline in age at pubertal onset in boys.

Sex differences in primary hypertension

Men have higher blood pressure than women through much of life regardless of race and ethnicity. This is a robust and highly conserved sex difference that it is also observed across species including dogs, rats, mice and chickens and it is found in induced, genetic and transgenic animal models of hypertension. Not only do the differences between the ovarian and testicular hormonal milieu contribute to this sexual dimorphism in blood pressure, the sex chromosomes also play a role in and of themselves. This review primarily focuses on epidemiological studies of blood pressure in men and women and experimental models of hypertension in both sexes. Gaps in current knowledge regarding what underlie male-female differences in blood pressure control are discussed. Elucidating the mechanisms underlying sex differences in hypertension may lead to the development of anti-hypertensives tailored to one's sex and ultimately to improved therapeutic strategies for treating this disease and preventing its devastating consequences.

Turner syndrome and sexual differentiation of the brain: implications for understanding male-biased neurodevelopmental disorders

Turner syndrome (TS) is one of the most common sex chromosome abnormalities. Affected individuals often show a unique pattern of cognitive strengths and weaknesses and are at increased risk for a number of other neurodevelopmental conditions, many of which are more common in typical males than typical females (e.g., autism and attention-deficit hyperactivity disorder). This phenotype may reflect gonadal steroid deficiency, haploinsufficiency of X chromosome genes, failure to express parentally imprinted genes, and the uncovering of X chromosome mutations. Understanding the contribution of these different mechanisms to outcome has the potential to improve clinical care for individuals with TS and to better our understanding of the differential vulnerability to and expression of neurodevelopmental disorders in males and females. In this paper, we review what is currently known about cognition and brain development in individuals with TS, discuss underlying mechanisms and their relevance to understanding male-biased neurodevelopmental conditions, and suggest directions for future research.

Analysis of urinary estrogens, their oxidized metabolites, and other endogenous steroids by benchtop orbitrap LCMS versus traditional quadrupole GCMS

Estrogens and other endogenous steroids are known risk markers for cancer. Gas chromatography (GC) with mass spectrometry (MS) has traditionally predominated the analysis of estrogens and other endogenous steroids, but liquid chromatography (LC) MS is increasingly favored. Direct comparisons of the two technologies have hitherto not been performed. Steroids were analyzed from 232 urine samples of 78 premenopausal women in a blinded fashion by benchtop orbitrap LCMS and single quadrupole GCMS. Sixteen steroidal estrogens including oxidized metabolites could be analyzed by LCMS. LCMS-GCMS Spearman rank correlations of the major estrogens E(1), E(2), E(3), 16α-OHE(1), and 2-OHE(1) were very high (r = 0.72-0.91), and absolute concentrations also agreed (<5% difference for E(1), E(2), E(3), 16α-OHE(1)). LCMS allowed reinterrogation of the acquired data due to orbitrap technology, which permitted post-analysis quantitation of progesterone, cortisol, and cortisone (LCMS-GCMS Spearman rank correlations = 0.80-0.84; absolute difference, <7%; n = 137). GCMS allows the measurement of a wide range of steroids including non-polar analytes that escape the presented LCMS assay. In contrast, orbitrap-based LCMS can detect more estrogens, is faster, less costly, allows post-data acquisition reinterrogation of certain analytes that had not been targeted a priori, and requires much less urine.

Prepubertal glucocorticoid status and pubertal timing

CONTEXT

Whether prepubertal glucocorticoid status impacts on the timing of puberty is not clear.

OBJECTIVE

The objective of the study was to examine the relationship between prepubertal glucocorticoid status and early or late pubertal markers, independent of adrenarchal and nutritional status.

DESIGN AND PARTICIPANTS

Prospective cohort study of healthy Caucasian children (n = 111, 56 boys) who provided both 24-h urine samples and weighed dietary records 1 and 2 yr before the start of pubertal growth spurt [age at take-off (ATO)].

MEASUREMENTS

Major urinary glucocorticoid and androgen metabolites determined by gas chromatography-mass spectrometry analysis were summed to assess daily overall cortisol (ΣC21) and adrenal androgen secretion; urinary free cortisol and cortisone measured by RIA were summed (UFF+UFE) as an indicator of potentially bioactive free glucocorticoids.

MAIN OUTCOMES

The main outcomes included ATO, age at peak height velocity, age at menarche/voice break, ages at Tanner stage 2 for breast (girls) and genital (boys) development, and pubic hair.

RESULTS

In girls ΣC21, but not UFF+UFE, was associated with pubertal markers after adjusting for overall adrenal androgen, urinary nitrogen, and body fat. Girls with higher ΣC21 (fourth quartile) reached ATO 0.7 yr (P = 0.01) and menarche 0.9 yr later (P = 0.006) than girls with lower ΣC21 (first quartile). The ΣC21 tended to be also positively associated with age at Tanner stage 2 for breast (P = 0.1), Tanner stage 2 for pubic hair (P = 0.1), and age at peak height velocity (P = 0.06). In boys, neither the ΣC21 nor UFF+UFE was related to pubertal timing.

CONCLUSION

An individually higher prepubertal glucocorticoid secretion level, even in physiological range, appears to delay early and late pubertal timing of healthy girls, particularly their onset of pubertal growth spurt and menarche.

Are Klinefelter boys hypogonadal?

Male hypogonadism implies decreased function of one or more testicular cell population, i.e. germ, Leydig and/or Sertoli cells. In the normal prepubertal boy, Sertoli cells are very active, as indicated by high anti-Müllerian hormone (AMH) and inhibin B secretion, whereas the functional activity of Leydig cells is minimal, as evidenced by low testosterone production, and germ cells do not undergo the full spermatogenic process. Klinefelter syndrome is the most frequent cause of hypogonadism in the adult male. In this review, we discuss whether the gonadal failure is already established during infancy and childhood. In Klinefelter syndrome, there is increased germ cells degeneration from mid-foetal life - resulting in a decreased number at birth - which persists during infancy and childhood and becomes dramatic during puberty. Controversial results exist in the literature regarding Leydig cell function in Klinefelter boys: while some authors have found normal to low testosterone levels in infancy and childhood, others have reported normal to high values. Sertoli cell products AMH and inhibin B are normal in prepubertal boys and only decline during mid- to late puberty.

CONCLUSION

Klinefelter syndrome is a primary hypogonadism affecting all testicular cell populations. Germ cells are affected from foetal life, and a severe depletion occurs at puberty. Leydig cell function may be normal or mildly affected in foetal and early postnatal life. Sertoli cell function is not impaired until mid- to late puberty, as reflected by normal AMH and inhibin B in Klinefelter boys.

A novel GC-MS method in urinary estrogen analysis from postmenopausal women with osteoporosis

Estrogen metabolites play important roles in the development of female-related disorders and homeostasis of the bone. To improve detectability, a validated gas chromatography-mass spectrometry (GC-MS) method was conducted with two-phase extractive ethoxycarbonlyation (EOC) and subsequent pentafluoropropionyl (PFP) derivatization was introduced. The resulting samples were separated through a high-temperature MXT-1 column within an 8 min run and were detected in the selected ion monitoring (SIM) mode. The optimized analytical conditions led to good separation with a symmetric peak shape for 19 estrogens as their EOC-PFP derivatives. The limit of quantification (LOQ) was from 0.02 to ∼0.1 ng/ml for most estrogens analyzed, except for 2-hydroxyestriol (0.5 ng/ml). The devised method was found to be linear (r² > 0.995) in the range from the LOQ to 40 ng/ml, whereas the precision (% CV) and accuracy (% bias) ranged from 1.4 to 10.5% and from 91.4 to 108.5%, respectively. The good sensitivity and selectivity of this method even allowed quantification of the estrogen metabolites in urine samples obtained from the postmenopausal female patients with osteoporosis. The present technique can be useful for clinical diagnosis as well as to better understand the pathogenesis of estrogen-related disorders in low-level quantification.

Growth hormone plus childhood low-dose estrogen in Turner's syndrome

BACKGROUND

Short stature and ovarian failure are characteristic features of Turner's syndrome. Although recombinant human growth hormone is commonly used to treat the short stature associated with this syndrome, a randomized, placebo-controlled trial is needed to document whether such treatment increases adult height. Furthermore, it is not known whether childhood estrogen replacement combined with growth hormone therapy provides additional benefit. We examined the independent and combined effects of growth hormone and early, ultra-low-dose estrogen on adult height in girls with Turner's syndrome.

METHODS

In this double-blind, placebo-controlled trial, we randomly assigned 149 girls, 5.0 to 12.5 years of age, to four groups: double placebo (placebo injection plus childhood oral placebo, 39 patients), estrogen alone (placebo injection plus childhood oral low-dose estrogen, 40), growth hormone alone (growth hormone injection plus childhood oral placebo, 35), and growth hormone-estrogen (growth hormone injection plus childhood oral low-dose estrogen, 35). The dose of growth hormone was 0.1 mg per kilogram of body weight three times per week. The doses of ethinyl estradiol (or placebo) were adjusted for chronologic age and pubertal status. At the first visit after the age of 12.0 years, patients in all treatment groups received escalating doses of ethinyl estradiol. Growth hormone injections were terminated when adult height was reached.

RESULTS

The mean standard-deviation scores for adult height, attained at an average age of 17.0±1.0 years, after an average study period of 7.2±2.5 years were -2.81±0.85, -3.39±0.74, -2.29±1.10, and -2.10±1.02 for the double-placebo, estrogen-alone, growth hormone-alone, and growth hormone-estrogen groups, respectively (P<0.001). The overall effect of growth hormone treatment (vs. placebo) on adult height was a 0.78±0.13 increase in the height standard-deviation score (5.0 cm) (P<0.001); adult height was greater in the growth hormone-estrogen group than in the growth hormone-alone group, by 0.32±0.17 standard-deviation score (2.1 cm) (P=0.059), suggesting a modest synergy between childhood low-dose ethinyl estradiol and growth hormone.

CONCLUSIONS

Our study shows that growth hormone treatment increases adult height in patients with Turner's syndrome. In addition, the data suggest that combining childhood ultra-low-dose estrogen with growth hormone may improve growth and provide other potential benefits associated with early initiation of estrogen replacement. (Funded by the National Institute of Child Health and Human Development and Eli Lilly; ClinicalTrials.gov number, NCT00001221.).

Gender-specific association of the brain-derived neurotrophic factor gene with attention-deficit/hyperactivity disorder

OBJECTIVE

Attention-deficit/hyperactivity disorder (ADHD) is a complex neurodevelopmental disorder with a strong genetic component. Brain-derived neurotrophic factor (BDNF), which participates in the differentiation and survival of dopaminergic and noradrenergic neurons, could play a role in ADHD development. We aimed to explore the relationships between ADHD and BDNF gene polymorphism.

METHODS

We conducted a case-control analysis of 202 ADHD subjects and 159 controls, performed a transmission disequilibrium test on 151 trios, and compared the results of a continuous performance test (CPT) according to the genotype of the three single nucleotide polymorphisms (rs11030101, rs6265, rs16917204) in the BDNF gene.

RESULTS

In the case-control analysis, the AA genotype of the BDNF rs11030101 polymorphism was significantly associated with ADHD only in girls (p=0.024, odds ratio=3.00). The T-G-G haplotype was significantly less frequent (p=0.005) and A-G-G was more frequent (p=0.048) in girls with ADHD than in control girls (global p=0.027). A multivariate analysis of variance for commission errors on the CPT showed a significant main effect for the rs11030101 genotype (p=0.026) and an interaction effect of the rs11030101 genotype and gender (p=0.032) in ADHD probands.

CONCLUSION

These results provide preliminary evidence for a gender-specific association between BDNF and ADHD in the Korean population.

Prepubertal urinary estrogen excretion and its relationship with pubertal timing

Whether prepubertal estrogen production impacts on the timing of puberty is not clear. We aimed to investigate prepubertal 24-h estrogen excretion levels and their association with early and late pubertal markers. Daily urinary excretion rates of estrogens of 132 healthy children, who provided 24-h urine samples 1 and 2 yr before the start of the pubertal growth spurt [age at takeoff (ATO)], were quantified by stable isotope dilution/GC-MS. E-sum3 (estrone + estradiol + estriol) was used as a marker for potentially bioactive estrogen metabolites and E-sum5 (E-sum3 + 16-epiestriol + 16-ketoestradiol) for total estrogen production. Pubertal outcomes were ATO, age at peak height velocity (APHV), duration of pubertal growth acceleration (APHV-ATO), age at Tanner stage 2 for pubic hair (PH2), genital (G2, boys) and breast (B2, girls) development, and age at menarche. Prepubertal urinary estrogen excretions (E-sum3 and E-sum5) were not associated with ATO, APHV, and age at PH2 but with duration of pubertal growth acceleration (P < 0.01) in both sexes. Girls with higher E-sum3 reached B2 0.9 yr (P = 0.04) and menarche 0.3 yr earlier (P = 0.04) than girls with lower E-sum3. E-sum3 was not associated with age at G2 in boys (P = 0.6). For most pubertal variables, the associations with E-sum3 were stronger than with E-sum5. In conclusion, prepubertal estrogens may not be critical for the onset of the pubertal growth spurt but are correlated with its duration in both boys and girls. Prepubertal estrogen levels may already predict the timing of girls' menstruation and breast development but do not appear to affect sexual maturation in boys.

The challenge of assessing infant vaccine responses in resource-poor settings

Newborns and infants are highly susceptible to infectious diseases, resulting in high mortality and morbidity, particularly in resource-poor settings. Many vaccines require several booster doses, resulting in an extensive vaccine schedule, and yet there is still inadequate protection from some of these diseases. This is partly due to the immaturity of the neonate and infant immune system. Little is known about the specific modifications to immunological assessment protocols in early life but increasing knowledge of infant immunology has helped provide better recommendations for assessing these responses. Since most new vaccines will eventually be deployed in low-income settings such as Africa, the logistics and resources of assessing immunity in such settings also need to be understood. In this article, we will review immunity to vaccines in early life, discuss the many challenges associated with assessing immunogenicity and provide practical tips.

Steroid assays in paediatric endocrinology

Most steroid disorders of the adrenal cortex come to clinical attention in childhood and in order to investigate these problems, there are many challenges to the laboratory which need to be appreciated to a certain extent by clinicians. The analysis of sex steroids in biological fluids from neonates, over adrenarche and puberty present challenges of specificities and concentrations often in small sample sizes. Different reference ranges are also needed for interpretations. For around 40 years, quantitative assays for the steroids and their regulatory peptide hormones have been possible using immunoassay techniques. Problems are recognised and this review aims to summarise the benefits and failings of immunoassays and introduce where tandem mass spectrometry is anticipated to meet the clinical needs for steroid analysis in paediatric endocrine investigations. It is important to keep a dialogue between clinicians and the laboratory, especially when any laboratory result does not make sense in the clinical investigation.