Update on pubertal development

Heritability of Testosterone Levels in 12-Year-Old Twins and Its Relation to Pubertal Development

The aim of this study was to estimate the heritability of variation in testosterone levels in 12-year-old children, and to explore the overlap in genetic and environmental influences on circulating testosterone levels and androgen-dependent pubertal development. Midday salivary testosterone samples were collected on 2 consecutive days in a sample of 183 unselected twin pairs. Androgen-induced pubertal development was assessed using self-report Tanner scales of pubic hair development (boys and girls) and genital development (boys). A significant contribution of genetic effects to the variance in testosterone levels was found. Heritability was approximately 50% in both boys and girls. The remaining proportion of the variance in testosterone levels could be explained by nonshared environmental influences. The relatively high correlation between testosterone levels of opposite-sex dizygotic twins suggests that sex differences in genes influencing variation in testosterone levels have not yet developed in preand early puberty. Variance in pubertal development was explained by a large genetic component, moderate shared environmental influences, and a small nonshared environmental effect. Testosterone levels correlated moderately (r = .31) with pubertal development; the covariance between testosterone levels and pubertal development was entirely accounted for by genetic influences.

Stress and the hypothalamic pituitary adrenal axis in the developmental course of schizophrenia

Diathesis-stress models of schizophrenia and other psychotic disorders have dominated theorizing about etiology for over three decades. More recently, with advances in our understanding of the biological processes mediating the effects of stress, these models have incorporated mechanisms to account for the adverse impact of stress on brain function. This review examines recent scientific findings on the role of the hypothalamic-pituitary-adrenal (HPA) axis, one of the primary neural systems triggered by stress exposure, in the expression of vulnerability for schizophrenia. The results indicate that psychotic disorders are associated with elevated baseline and challenge-induced HPA activity, that antipsychotic medications reduce HPA activation, and that agents that augment stress hormone (cortisol) release exacerbate psychotic symptoms. The cumulative findings are discussed in light of a neural diathesis-stress model that postulates that cortisol has the potential to increase activity of dopamine pathways that have been implicated in schizophrenia and other psychotic disorders.

Pubertal neuromaturation, stress sensitivity, and psychopathology

Normal adolescent development is often accompanied by transient emotional and behavioral problems. For most individuals with postpubertal-onset adjustment problems, there is a resolution by early adulthood and relative stability through the adult life span. But for a minority, adjustment problems escalate during adolescence and portend the development of serious mental illness in adulthood. In this article, we explore adolescent behavioral changes and neurodevelopmental processes that might contribute to stress sensitivity and vulnerability for the emergence of the mental disorders. Of particular interest is the role that hormonal changes might play in the expression of genetic vulnerabilities for psychopathology. Drawing on recent findings from clinical research and behavioral neuroscience, we describe the ways in which postpubertal hormones might alter brain function and, thereby, behavior. It is concluded that there are both activational and organization effects of hormones on the adolescent brain, and these contribute to developmental discontinuities in behavioral adjustment. Implications for adult psychopathology and preventive intervention are discussed.

Changing ecological determinants of conduct problems from early adolescence to early adulthood

Changes in conduct problems from middle school through early adulthood were examined in a sample of 1191 African American and White males and females. Predictors were selected from a number of ecological contexts to examine the relative contribution of family, peer, school, and neighborhood factors to conduct problems during the 7th, 8th, and 11th grade and across transitions in middle school, into high school, and into young adulthood. Almost all contexts made a unique contribution to conduct problems except for the neighborhood setting. The variables that had the most regular influences during each of these periods were Family Consistent Control, Family Discipline Harshness, and Negative Peers. Positive family and positive peer variables had less consistent relations to outcomes. School variables were more influential in middle school than later. Few gender or race differences were found in the patterning of predictors across time. Studies using only one or two settings as predictors of conduct problems, may provide a misleading picture of their impact by excluding other contextual influences.

Genetic and environmental influences on pubertal development: longitudinal data from Finnish twins at ages 11 and 14

To study sources of individual differences in pubertal development, the authors fit a sex-limitation common factor model to data reported, at ages 11 and 14 years, by 1,891 twin pairs on items that comprise the Pubertal Development Scale (PDS; A. C. Petersen, L. Crockett, M. Richards, & A. Boxer, 1988). The model divides variation into a general pubertal factor and item-specific variation and, in addition, decomposes it into constituent sources. In both boys and girls, genetic influences made the largest contribution to variance common to PDS items. Genetic and nonshared environmental factors accounted for variation specific to PDS items in boys, whereas for girls, common environmental influences were added for growth spurt and menarcheal status. For both common and item-specific variation, genetic effects were partially sex specific. Subsidiary analyses found accelerated maturation in both boys and girls who at age 14 were reared in father-absent homes.

Gender and puberty interact on the stress-induced activation of parvocellular neurosecretory neurons and corticotropin-releasing hormone messenger ribonucleic acid expression in the rat

Individual variations in hypothalamic-pituitary-adrenal (HPA) function are most evident at or beyond the time of puberty, when marked changes in sex steroid release occur. To explore the nature by which gender differences in HPA function emerge we examined in prepubertal (approximately 30-d-old) and postpubertal (approximately 60-d-old) male and female rats HPA activity under basal conditions and in response to 30 min of restraint. Within the ACTH-regulating, medial parvocellular portion of the paraventricular nucleus, restraint-induced Fos protein and arginine vasopressin heteronuclear RNA were lower in 60- than in 30-d-old males. No such age-related shift in the response of these synaptic and transcriptional markers of cellular activation occurred in female rats. Basal CRH mRNA expression levels in the paraventricular nucleus increased with age in female but not male rats. Conversely, only male rats showed an age-related increase in basal CRH mRNA in the central amygdala, suggesting that neuronal and neurosecretory CRH-expressing cell types are subject to different pubertal and gender influences. We conclude that gonadal regulation of the HPA axis develops via distinct mechanisms in males and females. Puberty-related shifts in parvocellular neurosecretory function in males are emphasized by stress-induced shifts in neuronal activation, whereas biosynthetic alterations dominate in female rats.

Typical adolescent sexual development

This article addresses the typical components that contribute to the development of adolescent sexuality. It defines the important terms that are addressed in the article, explains the roots of human sexuality from birth and childhood, and details three components of adolescent sexuality: biologic, psychologic, and social cultural. The concluding sections on sexual education and sexual risk-taking further explain key factors in the development of adolescent sexuality.

Adolescent sexuality and pregnancy

The adolescent pregnancy rate has decreased throughout the USA. However, compared with other industrialized countries, US rates remain high. Efforts to decrease the number of teenage pregnancies are centered on sex education, postponing sexual activity, and safe sex practices.

Precocious puberty in immigrant children: indications for treatment

Immigration from developing countries to Europe has greatly increased during the last few years. Very little information is available on children who immigrated with their biological family, thus this paper deals only with children immigrating by adoption. In recent years some studies have shown an increased incidence of precocious puberty among adopted children, but information on this issue is scanty. Several hypotheses have been put forward to explain precocious puberty in adopted children, including nutritional, ethnic and/or emotional factors. Untreated precocious puberty is associated with short stature and has social and psychological consequences in addition to those related to adoption. Therefore, indications for therapy need to be carefully planned. In adopted children age estimation is a possible source of error in timing of puberty as date of birth is often missing or inaccurate. Thus each child must be carefully evaluated.