Approaches to Identify Factors Associated with Pubertal Timing in Self-Limited Delayed Puberty.

INTRODUCTION: Children with self-limited delayed puberty (DP) (constitutional delay) enter puberty after variable waiting times, and the factors associated with their eventual pubertal timing are not well understood. METHODS: We conducted a retrospective study of 99 girls and 228 boys with self-limited DP at an academic medical center between 2000 and 2015. To define features and potential subtypes of self-limited DP, we performed group-based trajectory modeling on childhood growth and latent-variable factor analysis on clinical characteristics. We then conducted time-to-event analyses to identify associations with pubertal timing. RESULTS: We identified two distinct growth trajectories in individuals with self-limited DP: one with stable and the other with declining height percentiles. Latent-variable factor analysis identified five factors underlying clinical variation that appear to correspond to genetic height potential, body mass index, childhood growth, parental pubertal delay, and medical issues (attention-deficit/hyperactivity disorder and inhaled glucocorticoid use). We observed correlations between pubertal timing and bone age (p = 0.01), childhood height (p = 0.004), and midparental target height (p < 0.001), but not with parental pubertal delay or with testosterone treatment in boys. CONCLUSIONS: By illustrating the heterogeneity within self-limited DP and identifying factors underlying this heterogeneity, our study suggests that there may be multiple causes of self-limited DP. However, our ability to determine when puberty will eventually occur remains limited. Dissecting self-limited DP into its component subtypes may inform future studies of the mechanisms contributing to pubertal delay as well as studies of the short- and long-term outcomes of self-limited DP.

Timing of Pubertal Onset in Girls and Boys With Constitutional Delay.

CONTEXT: The decision whether to treat a child with delayed puberty with sex steroids is primarily based on patient, family, and provider preference. Knowing when children with constitutional delay eventually enter puberty would inform this decision. OBJECTIVE, DESIGN, SETTING, PARTICIPANTS, AND OUTCOME MEASURES: To estimate and compare rates of pubertal entry, we conducted a retrospective cohort study by reviewing medical records of children evaluated for delayed puberty at a large academic medical center between 2000 and 2015, extracting data on pubertal status for all clinical visits, then conducting time-to-event analyses. RESULTS: Of 392 girls and 683 boys with delayed puberty, constitutional delay was the most common cause, found in 32% of girls and 70% of boys. In a subcohort of 97 girls and 243 boys who were prepubertal at one or more visits, we observed a broad age range for pubertal entry, up to >16 years for girls and >17 years for boys. The probability of entering puberty within the next year for 12- to 15.5-year-old girls and 13.5- to 16.5-year-old boys with delayed puberty ranged between 38% and 74%. No differences in the rates of pubertal entry were seen between girls and boys after data harmonization. CONCLUSION: The broad range of ages at pubertal entry for children with constitutional delay challenges the concept that constitutional delay is merely an extreme of normal variation. Discussions with patients and families about management should consider the possibility that some children may need to wait years after presentation until puberty starts.

Effects of the Timing of Sex-Steroid Exposure in Adolescence on Adult Health Outcomes.

CONTEXT: Variation in pubertal timing is associated with a wide range of adult risks and outcomes, but it is unclear whether these associations are causal, and it is largely unknown whether these associations can be modified by treatment. EVIDENCE ACQUISITION: We conducted PubMed searches to identify Mendelian randomization (MR) studies on the influence of pubertal timing on adult health and studies on sex-steroid treatment of the following conditions associated with reduced reproductive endocrine function in adolescence: constitutional delay, Turner syndrome, and Klinefelter syndrome. EVIDENCE SYNTHESIS: Results of MR studies suggest that earlier pubertal timing increases body mass index; increases risk for breast, ovarian, endometrial, and prostate cancers; elevates fasting glucose levels and blood pressure; impairs lung capacity and increases risk for asthma; leads to earlier sexual intercourse and first birth; decreases time spent in education; and increases depressive symptoms in adolescence. Later pubertal timing appears to lower bone mineral density (BMD). Although studies of constitutional delay have not shown that sex-steroid treatment alters adult height or BMD, studies of girls with Turner syndrome and boys with Klinefelter syndrome suggest that earlier initiation of sex-steroid treatment improves physical and neurocognitive outcomes. CONCLUSIONS: Despite having some limitations, MR studies suggest that pubertal timing causally influences many adult conditions and disease risks. Studies of Turner syndrome and Klinefelter syndrome suggest that earlier sex-steroid exposure may have short- and long-term benefits. The mechanisms underlying these findings and the effects of trends and treatments affecting pubertal timing remain to be determined.

Laboratory exercise for studying the morphology of heat-denatured and amyloid aggregates of lysozyme by atomic force microscopy.

To facilitate learning advanced instrumental techniques, essential tools for visualizing biomaterials, a simple and versatile laboratory exercise demonstrating the use of Atomic Force Microscopy (AFM) in biomedical applications was developed. In this experiment, the morphology of heat-denatured and amyloid-type aggregates formed from a low-cost and well-characterized model protein, hen egg white lysozyme (HEWL), are compared. Structural differences between the amorphous and ordered particles are quantified using ImageJ for the analysis of AFM images as a postlaboratory assignment. The laboratory exercise allows the direct observation of changes in the protein structure and helps students to understand the operation of AFM, as well as protein folding and misfolding related to many physiological and pathological processes. The described protocol stands alone, but also fits well into a larger module on protein structure and function or microscopic techniques as it can be linked easily to existing laboratory exercises on these topics. It can be easily adapted to the upper level undergraduate laboratory courses with limited lab hours as well as graduate level courses to improve students' research skills. © 2017 by The International Union of Biochemistry and Molecular Biology, 46(2):162-171, 2018.