Exploring Racial Differences in Precocious Puberty among Girls: Implications for the Role of Environmental Factors Open Access

Abstract

A secular trend towards earlier pubertal onset has been documented in girls in the
United States, and numerous studies have demonstrated racial differences in pubertal
timing-specifically, earlier ages for pubertal landmarks in black girls compared to white
girls-with indications that racial divergences may be a recent phenomenon. Neither of
these observations has been fully explained, and few studies have examined clinically
early puberty and racial differences in precocious puberty patients. This thesis therefore
aimed to assess racial variations in the distribution of precocious puberty subtypes and in
other patient characteristics through a review of medical records in order to better
illuminate racial differences in puberty and possible pathways through which
environmental exposures suspected to influence pubertal development may be
contributing to observed patterns.

Results indicated substantial differences in the distribution of subtypes, though
significant only at the 10% α level (p=0.076). Among 50 black patients, 26% had
premature adrenarche, 28% had premature thelarche, 28% had central precocious
puberty, and 18% had other forms of early puberty compared to 49%, 12%, 23%, and
16% in 49 white patients, respectively. A greater proportion of blacks were under 6 years
than whites (42% vs. 12%), and blacks appeared younger on average in each subtype.
The percentage of patients with potential neurologic causes of central precocious puberty
was considerably greater in whites (46% vs. 14%). Racial differences in estradiol levels
varied across subtypes. Additionally, low income and BMI were significantly higher in
black patients overall and showed similar differences by subtype.

These results suggest that factors known to affect pubertal timing and to vary by
race, such as BMI and income, do not account for racial differences in pubertal timing as
they remain significantly different among only cases of early puberty. Moreover, the fact
that most patients' puberty is not regulated by the true central mechanism, as in central
precocious puberty, may support the notion that environmental influences are promoting
hormonal activity outside of the main pathway. Moreover, a greater frequency of breast
development and subtypes involving estrogen effects in black girls may support claims of
higher estrogen-active environmental exposures among blacks.

Table of Contents

Table of Contents

Chapter 1: Introduction ....................................................................................................... 1
1.1 Precocious Puberty................................................................................................... 2
1.2 Assessment of Precocious Puberty .......................................................................... 5
1.3 Management of Precocious Puberty ........................................................................ 7
1.4 Pubertal Timing in US girls ..................................................................................... 8
1.5 Factors Influencing the Timing of Puberty ............................................................ 11
1.6 Disagreements over Pubertal Timing-Normal and Abnormal ............................ 20
1.7 Consequences of Early Puberty ............................................................................. 22
1.8 Study Aims & Significance ................................................................................... 23
Chapter 2: Methods ........................................................................................................... 25
2.1 Study Population .................................................................................................... 25
2.2 Data Collection and Measurements ....................................................................... 28
2.2.1 Diagnosis......................................................................................................... 28
2.2.2 Etiologies & Comorbidites ............................................................................. 29
2.2.3 Body Mass Index ............................................................................................ 30
2.2.4 Income Level .................................................................................................. 31
2.2.5 Age .................................................................................................................. 32
2.2.6 Estradiol .......................................................................................................... 32
2.3 Statistical Analysis ................................................................................................. 33
2.4 Hypotheses .............................................................................................................. 34
Chapter 3: Results ............................................................................................................. 36
3.1 Diagnoses ............................................................................................................... 36

3.2 Etiologies & Comorbidities ................................................................................... 36
3.3 Patient Characteristics ............................................................................................ 39
3.3.1 Body Mass Index ............................................................................................ 39
3.3.2 Income Level .................................................................................................. 40
3.3.3 Age .................................................................................................................. 40
3.4 Estradiol Levels ..................................................................................................... 42
Chapter 4: Discussion ....................................................................................................... 45
4.1 Diagnoses ............................................................................................................... 45
4.2 Etiologies & Comorbidities ................................................................................... 48
4.3 Body Mass Index ................................................................................................... 52
4.4 Income Level ......................................................................................................... 54
4.5 Age ......................................................................................................................... 56
4.6 Estradiol Levels ..................................................................................................... 59
4.7 Strengths and Limitations ...................................................................................... 62
4.8 Future Directions ................................................................................................... 73
4.9 Conclusions ............................................................................................................ 76
References ......................................................................................................................... 80
Additional Sources ............................................................................................................ 91
Tables & Figures ............................................................................................................... 92
Appendix A: Abstraction Form ...................................................................................... 107

List of Tables and Figures

Table 1: Frequency of Diagnosis Categories by Race ...................................................... 92
Table 2: Proportion of Patients with Evidence of Any Neurologic Damage or CNS
Abnormality ...................................................................................................................... 93
Table 3: Summary Statistics of Patient BMI Z-Scores & Percentiles at Initial ECC
Evaluation ......................................................................................................................... 94
Table 4: Proportion of Patients in Low Income Medical Insurance Programs by Diagnosis
........................................................................................................................................... 95
Table 5: Summary Statistics of Patient Age (yrs) at Initial Evaluation for Precocious
Puberty .............................................................................................................................. 96
Table 6: Summary Statistics of Estradiol Levels (pg/ml) by Diagnosis for Patients under
10 Years at the Time of Testing ........................................................................................ 97
Figure 1: Distribution of Patient BMI Z-Scores at Initial ECC Evaluation ...................... 98
Figure 2: Z-Scores of Patient BMI at Initial ECC Evaluation by Diagnosis .................... 99
Figure 3: Distribution of Patient Ages at Initial Evaluation for Precocious Puberty ...... 101
Figure 4: Age of Patients at Initial Evaluation for Precocious Puberty by Diagnosis .... 102
Figure 5: Distribution of Patients' First Estradiol Laboratory Result............................. 104
Figure 6: Estradiol Levels by Diagnosis for Patients under 10 Years at the Time of
Testing............................................................................................................................. 105

About this Master's Thesis

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• Permission granted by the author to include this thesis or dissertation in this repository. All rights reserved by the author. Please contact the author for information regarding the reproduction and use of this thesis or dissertation.

School	Rollins School of Public Health
Department	Environmental Health
Degree	MPH
Submission	Master's Thesis
Language	English
Research Field	Health Sciences, Public Health Sociology, Ethnic and Racial Studies Health Sciences, Epidemiology
Keyword	pubertal onset body mass index precocious puberty premature thelarche pubertal development sexual precocity premature adrenarche sexual maturation menarche pubertal timing environmental exposures
Committee Chair / Thesis Advisor	Marcus, Michele, Emory University
Committee Members	Tolbert, Paige, Emory University
Partnering Agencies	Emory University schools, faculty or affiliated programs Hospital or other health care provider

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