a Hospital Sant Joan de Déu, University of Barcelona, Barcelona, Spain
b Department of Pediatrics, University of Leuven, Leuven, Belgium
| ABSTRACT |
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METHODS. We studied 187 PP girls longitudinally: (1) at birth, (2) in prepuberty, (3) at onset of puberty, (4) at menarche, and (5) on reaching adult stature. This PP cohort was divided into subgroups of higher birth weight (>0 SD), intermediate birth weight (0 to 2 SD), and lower birth weight (less than 2 SD).
RESULTS. At the time of PP diagnosis, age, bone age, and BMI were similar across birth weight subgroups; circulating sex hormonebinding globulin and body height were reduced in PP girls with lower birth weight, and these remained so throughout pubertal development. Onset of puberty occurred earlier in PP girls with lower birth weight; so did menarche. Adult height differed by an average of 6.5 cm (
1 SD) between the upper and lower birth weight subgroups; this difference was essentially achieved before puberty and even before PP. Menarche before age 12.0 years was twofold more prevalent in PP girls than in control subjects. Among PP girls, age at menarche was advanced by 8 to 10 months in lower versus higher birth weight girls. Menarche before age 12.0 years was threefold more prevalent among LBW-PP girls than in control subjects (
75% vs
25%).
CONCLUSIONS. The link between prenatal growth restraint and early menarche is herewith extended to PP girls. In particular LBW-PP girls may become a target group for interventions directed toward normalization of pubertal onset and progression.
Key Words: precocious pubarche adrenarche birth weight growth puberty height
Abbreviations: PPprecocious pubarche DHEASdehydroepiandrosterone-sulfate LBWlow birth weight SHBGsex hormonebinding globulin B2Tanner stage 2 for breast development SDSSD score
Girls with precocious pubarche (PP; pubic hair at <8 years of age) as a result of an early or amplified adrenarche (high circulating dehydroepiandrosterone-sulfate [DHEAS])1 tend to be hyperinsulinemic, in particular when born with low birth weight (LBW); this hyperinsulinemia is reflected, for example, by low insulin-like growth factor binding protein-1 and sex hormonebinding globulin (SHBG) levels and also by a central fat excess.13
The majority of LBW girls demonstrate vigorous catch-up growth in infancy and, by the age of 1 year, become insulin resistant4; by 2 years of age, they have normalized height and weight,5 and by 3 years of age, they start to have an adipose body composition.6 By 8 years of age, girls with the combination of a birth weight in the lower tertile and an actual weight in the upper tertile develop an amplified adrenarche7 that may be accompanied by PP (depending on background genotype) and that can be followed by hyperinsulinemic hyperandrogenism, so-called polycystic ovary syndrome.1, 811
Longitudinal follow-up of girls with PP has shown that, on average, these girls present an early-normal onset and progression of puberty and an adult stature within target height range.12 However, the interrelationships among prenatal growth, PP, the timing of puberty-menarche, and adult stature remain to be defined.
| Methods |
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The study population consisted only of girls in whom PP was ascribed to amplified adrenarche, as suggested by high serum androstenedione and/or DHEAS levels1; mean delay between pubic hair appearance and diagnostic evaluation was estimated to be in the 6- to 12-month range. None of the girls presented evidence for late-onset adrenal hyperplasia,14, 15 thyroid dysfunction, or diabetes or was receiving medications that are known to affect adrenal or gonadal function or carbohydrate or lipid metabolism.
Auxology
Height was measured with a Harpenden stadiometer and transformed into an SD score (SDS) according to Tanner references,16 which were appropriate for Catalan girls over the time span of follow-up.17 Adult height was considered to be reached when postmenarchal growth velocity had decreased to <0.5 cm/year and/or when bone age was
15 years. Target height was defined as midparental height, adjusted for female gender. BMI was calculated as a ratio of weight (in kilograms) to height squared (in meters) and was transformed into SDSs3; bone age was assessed by a single observer, according to the method of Greulich and Pyle.18
Birth weight data were transformed into SDSs for gestational age, as described.1 To assess the effect of birth weight on menarche and on auxologic and biochemical variables, the PP cohort was divided into subgroups of higher birth weight (>0 SD), intermediate birth weight (0 to 2 SD), and lower birth weight (less than 2 SD); at term birth, these SD values correspond to birth weights of approximately >3.4, 3.4 to 2.5, and <2.5 kg.1
Hormonal Assessment and Assays, Statistics, and Ethics
In all girls, serum SHBG levels were assessed by immunochemiluminescence (Immulite 2000; Diagnostic Products, Los Angeles, CA); 17-hydroxyprogesterone was measured by a commercial radioimmunoassay, as described.3 Samples were stored at 20°C until assay.
This study was approved by the institutional review board of Barcelona Hospital. Two-sided t tests (paired or unpaired, as appropriate) were used for comparisons; per variable, only 1 comparison was performed; significance level was set at P < .05. Selected results from part of this study population were previously reported within other contexts.1, 3, 8
| RESULTS |
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1 SD) between the upper and lower birth weight subgroups. This difference was essentially achieved before puberty and even before PP; pubertal height gain was strikingly similar in all birth weight groups.
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90% of girls in both the PP and the general population are still premenarcheal. Before the age of 12.0 years, however, the prevalence of menarche doubles in PP girls, as compared with the general population. At the age of 12.8 years, the fraction of premenarcheal girls is fivefold larger in the general population than among PP girls.
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75% vs
25%).
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| DISCUSSION |
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6 months, and menarche is also advanced by
6 months, or by even more.22, 23 Among girls who start puberty at 8 years of age, menarche occurs 1 year earlier in LBW than in non-LBW girls, and such rapid pubertal progression may contribute to shortening adult stature.24 However, the main cause of the relatively short adult stature of LBW-PP girls seems to be their prenatal growth restraint, because most of their height loss occurred before puberty and even before PP. In population studies, early menarche has been associated with fat excess and with higher fasting levels of insulin.25, 26 Given that both LBW and PP girls are characterized by hyperinsulinemia,2729 the present findings could be interpreted as suggestive of a stimulatory role for hyperinsulinemia (and/or its correlates) in the tempo of pubertal progression. From prepuberty to postmenarche, LBW-PP girls displayed low levels of circulating SHBG, which is a marker of hyperinsulinemic insulin resistance in nondiabetic girls.30 In LBW-PP girls, not only the low levels of SHBG but also the hyperleptinemia may participate in the acceleration of both the onset and progression of puberty.30, 31
The link between prenatal growth restraint and early menarche, as previously established for girls with early-normal onset of puberty,24 is herewith extended to girls with PP. The described acceleration of pubertal onset and progression remains to be confirmed in ethnic or other populations with a relatively high prevalence of LBW, early pubarche, overweight, and, maybe, high androgen sensitivity.9, 25, 26, 32, 33 If the present findings are confirmed, then LBW-PP girls may become a target group for interventions that are directed not only toward prevention of hyperinsulinemic hyperandrogenism10, 34 but also toward normalization of pubertal onset and progression.
| ACKNOWLEDGMENTS |
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We thank Carme Valls for hormone measurements.
| FOOTNOTES |
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Address correspondence to Lourdes Ibáñez, MD, PhD, Endocrinology Unit, Hospital Sant Joan de Déu, University of Barcelona, Passeig de Sant Joan de Déu, 2, 08950 Esplugues, Barcelona, Spain. E-mail: libanez{at}hsjdbcn.org
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