Annette Mouritsen

Recent Secular Trends in Pubertal Timing: Implications for Evaluation and Diagnosis of Precocious Puberty

The decline in age at puberty in the general population has been paralleled by an increase in the number of girls referred for evaluation of precocious puberty (PP). In 1999, The Lawson Wilkins Pediatric Endocrine Society recommended a lowering of the age limit for evaluation of PP in girls. However, the limited evidence on which these recommendations were based led many experts to question these new suggestions. The emergence of new European pubertal timing data evaluated by robust clinical as well as biochemical markers has broadened our insight on how to interpret the recent pubertal changes. The recent pubertal trends have resulted in a concomitant lowering of the lower limit of normality of the pubertal onset. However, evidence suggests that age at the gonadotropin and sex steroid surges have not changed. Thus, it looks as if an increasing proportion of contemporary early pubertal girls may experience isolated gonadotropin-independent thelarche rather than central PP, which may not be discernible on pubertal examination alone. Thus, the population-based limits of normality should not be directly translated into revision of age limits for evaluation of PP due to the risk of misdiagnosing rapid progressive PP as well as intracranial and other underlying pathology.

Changes in Anti-Müllerian Hormone (AMH) throughout the Life Span: A Population-Based Study of 1027 Healthy Males from Birth (Cord Blood) to the Age of 69 Years

CONTEXT Anti-Müllerian hormone (AMH), which is secreted by immature Sertoli cells, triggers the involution of the fetal Müllerian ducts. AMH is a testis-specific marker used for diagnosis in infants with ambiguous genitalia or bilateral cryptorchidism. AIM The aim of the study was to describe the ontogeny of AMH secretion through life in healthy males. SETTING This was a population-based study of healthy volunteers. PARTICIPANTS PARTICIPANTS included 1027 healthy males from birth (cord blood) to 69 yr. A subgroup was followed up longitudinally through the infantile minipuberty [(in cord blood, and at 3 and 12 months), n=55] and another group through puberty [(biannual measurements), n=83]. MAIN OUTCOME MEASURES Serum AMH was determined by a sensitive immunoassay. Serum testosterone, LH, and FSH were measured, and pubertal staging was performed in boys aged 6 to 20 yr (n=616). RESULTS Serum AMH was above the detection limit in all samples with a marked variation according to age and pubertal status. The median AMH level in cord blood was 148 pmol/liter and increased significantly to the highest observed levels at 3 months (P<0.0001). AMH declined at 12 months (P<0.0001) and remained at a relatively stable level throughout childhood until puberty, when AMH declined progressively with adults exhibiting 3-4% of infant levels. CONCLUSION Based on this extensive data set, we found detectable AMH serum levels at all ages, with the highest measured levels during infancy. At the time of puberty, AMH concentrations declined and remained relatively stable throughout adulthood. The potential physiological role of AMH and clinical applicability of AMH measurements remain to be determined.

Hypothesis: exposure to endocrine-disrupting chemicals may interfere with timing of puberty

A recent decline in onset of puberty - especially among girls - has been observed, first in the US in the mid-1990s and now also in Europe. The development of breast tissue in girls occurs at a much younger age and the incidence of precocious puberty (PP) is increasing. Genetic factors and increasing prevalence of adiposity may contribute, but environmental factors are also likely to be involved. In particular, the widespread presence of endocrine-disrupting chemicals (EDCs) is suspected to contribute to the trend of earlier pubertal onset. The factors regulating the physiological onset of normal puberty are poorly understood. This hampers investigation of the possible role of environmental influences. There are many types of EDCs. One chemical may have more than one mode of action and the effects may depend on dose and duration of the exposure, as well as the developmental stage of the exposed individual. There may also be a wide range of genetic susceptibility to EDCs. Human exposure scenarios are complex and our knowledge about effects of mixtures of EDCs is limited. Importantly, the consequences of an exposure may not be apparent at the actual time of exposure, but may manifest later in life. Most known EDCs have oestrogenic and/or anti-androgenic actions and only few have androgenic or anti-oestrogenic effects. Thus, it appears plausible that they interfere with normal onset of puberty. The age at menarche has only declined by a few months whereas the age at breast development has declined by 1 year; thus, the time span from initiation of breast development to menarche has increased. This may indicate an oestrogen-like effect without concomitant central activation of the hypothalamic-pituitary axis. The effects may differ between boys and girls, as there are sex differences in age at onset of puberty, hormonal profiles and prevalence of precocius puberty.

High urinary phthalate concentration associated with delayed pubarche in girls

Phthalates are a group of chemicals present in numerous consumer products. They have anti-androgenic properties in experimental studies and are suspected to be involved in human male reproductive health problems. A few studies have shown associations between phthalate exposure and changes in pubertal timing among girls, although controversies exist. We determined the concentration of 12 phthalate metabolites in first morning urine samples from 725 healthy Danish girls (aged 5.6-19.1 years) in relation to age, pubertal development (breast and pubic hair stage) and reproductive hormone levels (luteinizing hormone, oestradiol and testosterone). Furthermore, urinary phthalates were determined in 25 girls with precocious puberty (PP). In general, the youngest girls with less advanced pubertal development had the highest first morning urinary concentration of the monobutyl phthalate isoforms (∑MBP((i+n))), monobenzyl phthalate (MBzP), metabolites of di-(2-ethylhexyl) phthalate (∑DEHPm) and of di-iso-nonyl phthalate (∑DINPm). After stratification of the urinary phthalate excretion into quartiles, we found that the age at pubarche was increasing with increasing phthalate metabolite quartiles (except for MEP). This trend was statistically significant when all phthalate metabolites (except MEP) were summarized and expressed as quartiles. No association between phthalates and breast development was observed. In addition, there were no differences in urinary phthalate metabolite levels between girls with PP and controls. We demonstrated that delayed pubarche, but not thelarche, was associated with high phthalate excretion in urine samples from 725 healthy school girls, which may suggest anti-androgenic actions of phthalates in our study group of girls.

Individual serum levels of anti-Müllerian hormone in healthy girls persist through childhood and adolescence: a longitudinal cohort study

BACKGROUND In adult women, the circulating level of anti-Müllerian hormone (AMH) is a novel marker of ovarian function, as it reflects the number of remaining ovarian follicles. Therefore, AMH has gained widespread attention in fertility clinics, and a low AMH is believed to predict impaired fertility and imminent menopause. However, the natural course of circulating AMH levels during female childhood and adolescence is not known. METHODS Serum levels of AMH and FSH were measured in girls participating in The COPENHAGEN Puberty Study. Longitudinal part: 85 healthy girls and adolescents were examined, and blood samples were drawn every 6 months for an average of 3 years: median (range) number of samples per girl was 6 (2-10), age at baseline was 9.2 (5.9-12.9) years. Cross-sectional part: 224 prepubertal girls (age 8.3, 5.6-11.7 years) were examined and each girl had one blood sample drawn. RESULTS The individual mean AMH levels in girls followed longitudinally ranged from 5 to 54 pmol/l (median 18 pmol/l). The mean intra-individual coefficient of variation of AMH was 22% (range 0-54%). Overall, each girl maintained her AMH level throughout childhood and adolescence although minor, but significant, changes occurred during pubertal transition. In prepubertal girls, AMH was negatively correlated with FSH (r = -0.31, P < 0.001). Twelve per cent (10/85) had mean AMH below a cut-off value of 8 pmol/l, indicating that the interpretation of low AMH as a marker of approaching menopause may not apply to pre- and peri-pubertal girls. CONCLUSIONS Circulating AMH exhibits only minor fluctuations during childhood and adolescence, and a random AMH measurement seems representative for a given girl. The negative AMH-FSH correlation in prepubertal girls supports the notion that AMH is a quantitative marker of ovarian follicles even in young girls.

Validity of Self-Assessment of Pubertal Maturation

BACKGROUND AND OBJECTIVES: Studies of adolescents often use self-assessment of pubertal maturation, the reliability of which has shown conflicting results. We aimed to examine the reliability of child and parent assessments of healthy boys and girls. METHODS: A total of 898 children (418 girls, 480 boys, age 7.4–14.9 years) and 1173 parents (550 daughters, 623 sons, age 5.6–14.7 years) assessed onset of puberty or development of breasts, genitals, and pubic hair according to Tanner stages by use of a questionnaire and drawings. Physicians’ assessments were blinded and set as the gold standard. Percentage agreement, κ, and Kendall’s correlation were used to analyze the agreement rates. RESULTS: Breast stage was assessed correctly by 44.9% of the girls (κ = 0.28, r = 0.74, P < .001) and genital stage by 54.7% of the boys (κ = 0.33, r = 0.61, P < .001). For pubic hair stage 66.8% of girls (κ = 0.55, r = 0.80, P < .001) and 66.1% of boys (κ = 0.46, r = 0.70, P < .001) made correct assessments. Of the parents, 86.2% correctly assessed onset of puberty in girls (κ = 0.70, r = 0.71, P < .001) and 68.4% in boys (κ = 0.30, r = 0.37, P < .001). Children who underestimated were younger and children who overestimated older than their peers who made correct assessments. Girls and their parents tended to underestimate, whereas boys overestimated their pubertal stage. CONCLUSIONS: Pubertal assessment by the child or the parents is not a reliable measure of exact pubertal staging and should be augmented by a physical examination. However, for large epidemiologic studies self-assessment can be sufficiently accurate for a simple distinction between prepuberty and puberty.

Diagnostic work-up of 449 consecutive girls who were referred to be evaluated for precocious puberty.

OBJECTIVE A decrease in age at pubertal onset has been observed internationally. The aim of this study was to describe a large cohort of Caucasian girls referred with signs of early puberty according to etiology and compare biochemical characteristics. METHODS In this single-center study, we included 449 consecutive Caucasian girls who were referred with signs of early puberty during the years 1993-2009. We evaluated pubertal stage, height, weight, and bone age. FSH, LH, estradiol, and inhibin B were determined, and a standard GnRH test was performed. Brain magnetic resonance imaging was performed to rule out pathologies. RESULTS During the period from 1993-2008, we found an increase in the number of girls in most diagnostic groups. Of 449 girls, 88 had central precocious puberty (CPP), and 12 of these had an organic origin. A total of 129 had early-normal variant (8-9 yr), 69 had premature thelarche, and 49 premature adrenarche. Receiver operating characteristic analyses revealed that basal LH was superior in predicting the maximal LH level during GnRH testing in comparison with FSH, estradiol, and inhibin B levels. Basal LH levels were above the age-related 2 sd in 26.2, 19.6, 65.1, and 75.0% of girls with, respectively, early-normal variant, premature thelarche, idiopathic CPP, and organic CPP, but LH levels below the detection limit were also seen among girls with a pubertal GnRH test. CONCLUSION We observed an increasing number of girls referred because of early pubertal signs. An elevated basal LH was highly predictive of a pubertal GnRH test result, whereas a low LH did not exclude central pubertal activation.

The 2014 Danish references from birth to 20 years for height, weight and body mass index

To construct new Danish growth charts for 0‐ to 20‐year‐olds and to compare them with Danish references from 1982 and with World Health Organization (WHO) standards for children aged 0–5 years from 2006, by applying similar inclusion and exclusion criteria.

The physiology and timing of male puberty.

Purpose of reviewTo 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 findingsAn 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. SummaryEvaluation 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.

The Pubertal Transition in 179 Healthy Danish Children: Associations between Pubarche, Adrenarche, Gonadarche and Body Composition

BACKGROUND Pubertal onset is usually defined by breast development in girls and testicular growth in boys. Pubarche is defined as the attainment of pubic hair and is considered as a sign of pubertal transition. Pubarche is preceded by a gradual increase in production of adrenal androgens, DHEA and Δ4-androstenedione (Adione), a process termed adrenarche. OBJECTIVE To study the natural course of pubertal transition and the associations with adrenarche, body fat, and linear growth. DESIGN AND METHODS A longitudinal study of 179 healthy children (89 girls) with higher socioeconomic background examined every 6 months for 5 years. Pubic hair stage, breast stage, genital stage, testicular volume (TV), height, weight, and four skinfolds were measured. RESULTS In girls, median age (25th and 75th percentiles) at thelarche (B2+) was 10.1 years (9.3-10.9). In boys, median age at attaining a TV >3 ml was 11.5 years (10.9-12.0). Median age at pubarche (PH2+) was 10.9 years (10.3-11.4) in girls and 11.6 years (10.8-12.4) in boys. Only 6.8% (4/59) of the girls and 24.6% (15/61) of the boys developed pubic hair as the first isolated sign of puberty. Serum DHEAS and Adione increased with age, although the increase in Adione was most pronounced in girls. No associations between early age at thelarche/testicular growth and increased body fat (BMI and sum of four skinfolds) were observed. CONCLUSION Danish children rarely experience pubarche as the first sign of puberty. No associations between age at pubertal onset and body composition were found. Circulating levels of Adione, but not DHEAS, increased with the onset of puberty, although with large interindividual variability.