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SEXUAL DIMORPHISM

Sociologyindex, Sociology Books 2012

Sexual dimorphism is the differences between males and females in size and appearance.

Sexual dimorphism in humans is greater than in some animals and less than in many.

Evolutionary psychologists and biologists are intrigued to understand the function of sexual dimorphism.

Depression is twice as common in women as in men, but the reason for this sexual dimorphism is unknown.

Pelvic Politics: Sexual Dimorphism and Racial Difference 
Sally Markowitz, Signs, Vol. 26, No. 2 (Winter, 2001)

Snips and Snails and Theorists' Tales: Classical Sociological Theory and the Making of 'Sex' - Exploring how the emerging discipline of sociology both drew on and contributed to the construction of a scientifically grounded sexual dimorphism.
Barbara L. Marshall, Trent University, Canada 
This article locates classical sociology within the context of widely circulating scientific 'truths' about sexed bodies, exploring how the emerging discipline of sociology both drew on and contributed to the construction of a scientifically grounded sexual dimorphism. Through an examination of Durkheim's theory of conjugal society and Weber's writings on the routinization of sexual conduct, the extent to which anxieties about masculine sexuality animated classical conceptions of the shifting mind/body relationship in modernity is illuminated. This is read alongside a shared problematic in the sexual science of the time - concern over the relationship between 'modern' life and male sexual dysfunction. I argue that the manner in which both sociology and sexual science problematized male sexuality as a pivotal issue of modernity is illustrative of the construction of a fundamentally gendered ontology of the social. I argue that the actively internalized struggle of mind and body in sociology's men renders them universally individual, whilst its women are collectively particular, and that this is a legacy with which social theory continues to struggle. - jcs.sagepub.com/cgi/content/abstract/2/2/135

Normal Sexual Dimorphism of the Adult Human Brain Assessed by In Vivo Magnetic Resonance Imaging 
Jill M. Goldstein, Larry J. Seidman, Nicholas J. Horton, Nikos Makris, David N. Kennedy, Verne S. Caviness, Jr, Stephen V. Faraone and Ming T. Tsuang
The etiology and consistency of findings on normal sexual dimorphisms of the adult human brain are unresolved. In this study, we present a comprehensive evaluation of normal sexual dimorphisms of cortical and subcortical brain regions, using in vivo magnetic resonance imaging, in a community sample of 48 normal adults. The men and women were similar in age, education, ethnicity, socioeconomic status, general intelligence and handedness. Forty-five brain regions were assessed based on T1-weighted three-dimensional images acquired from a 1.5 T magnet. Sexual dimorphisms of adult brain volumes were more evident in the cortex, with women having larger volumes, relative to cerebrum size, particularly in frontal and medial paralimbic cortices. Men had larger volumes, relative to cerebrum size, in frontomedial cortex, the amygdala and hypothalamus. A permutation test showed that, compared to other brain areas assessed in this study, there was greater sexual dimorphism among brain areas that are homologous with those identified in animal studies showing greater levels of sex steroid receptors during critical periods of brain development. These findings have implications for developmental studies that would directly test hypotheses about mechanisms relating sex steroid hormones to sexual dimorphisms in humans.

Regulation of Sexual Dimorphism in Mammals 
CHRISTOPHER M. HAQQ AND PATRICIA K. DONAHOE 
Pediatric Surgical Research Laboratories, Massachusetts General Hospital, and Department of Genetics and Surgery, Harvard Medical School, Boston, Massachusetts 
Haqq, Christopher M., and Patricia K. Donahoe. Regulation of Sexual Dimorphism in Mammals. Physiol. Rev. 78: 1-33, 1998. Sexual dimorphism in humans has been the subject of wonder for centuries. In 355 BC, Aristotle postulated that sexual dimorphism arose from differences in the heat of semen at the time of copulation. In his scheme, hot semen generated males, whereas cold semen made females (Jacquart, D., and C. Thomasset. Sexuality and Medicine in the Middle Ages, 1988). In medieval times, there was great controversy about the existence of a female pope, who may have in fact had an intersex phenotype (New, M. I., and E. S. Kitzinger. J. Clin. Endocrinol. Metab. 76: 3-13, 1993.). Recent years have seen a resurgence of interest in mechanisms controlling sexual differentiation in mammals. Sex differentiation relies on establishment of chromosomal sex at fertilization, followed by the differentiation of gonads, and ultimately the establishment of phenotypic sex in its final form at puberty. Each event in sex determination depends on the preceding event, and normally, chromosomal, gonadal, and somatic sex all agree. There are, however, instances where chromosomal, gonadal, or somatic sex do not agree, and sexual differentiation is ambiguous, with male and female characteristics combined in a single individual. In humans, well-characterized patients are 46, XY women who have the syndrome of pure gonadal dysgenesis, and a subset of true hermaphrodites are phenotypic men with a 46, XX karyotype. Analysis of such individuals has permitted identification of some of the molecules involved in sex determination, including SRY (sex-determining region Y gene), which is a Y chromosomal gene fulfilling the genetic and conceptual requirements of a testis-determining factor. The purpose of this review is to summarize the molecular basis for syndromes of sexual ambiguity seen in human patients and to identify areas where further research is needed. Understanding how sex-specific gene activity is orchestrated may provide insight into the molecular basis of other cell fate decisions during development which, in turn, may lead to an understanding of aberrant cell fate decisions made in patients with birth defects and during neoplastic change. - physrev.physiology.org/cgi/content/abstract/78/1/1

Sexual Dimorphism in Counterregulatory Responses to Hypoglycemia after Antecedent Exercise - Pietro Galassetti, Anthony R. Neill, Donna Tate, Andrew C. Ertl, David H. Wasserman and Stephen N. Davis 
Departments of Medicine and Molecular Physiology and Biophysics, Vanderbilt University School of Medicine and Nashville Veteran Affairs Medical Center, Nashville, Tennessee 37232-6303 
Address all correspondence and requests for reprints to: Pietro Galassetti, M.D., Ph.D., 712 MRB II, Division of Diabetes and Endocrinology, Vanderbilt University Medical School, Nashville, Tennessee 37232-6303.
Abstract: After antecedent hypoglycemia, counterregulatory responses to subsequent hypoglycemia exhibit greater blunting in men than in women. Because physical exercise and hypoglycemia share multiple counterregulatory mechanisms, we hypothesized that prior exercise may also result in gender-specific blunting of counterregulatory responses to subsequent hypoglycemia. Thirty healthy subjects (15 women and 15 men; age, 28 ± 3 yr; body mass index, 23 ± 1 kg/m2) were studied during 2-d experiments. Day 1 consisted of either identical 90-min morning and afternoon cycle exercise at 50% maximum oxygen expenditure or two 2-h episodes of hyperinsulinemic euglycemia. Day 2 consisted of a 2-h morning hyperinsulinemic-hypoglycemic clamp. Endogenous glucose production was measured using [3-3H]glucose. Muscle sympathetic nerve activity was measured using microneurography. Day 2 insulin (540 ± 36 pmol/liter) and plasma glucose (2.9 ± 0.06 pmol/liter) levels were similar in men and women during the last 30 min of hypoglycemia. Compared with antecedent euglycemia, d 1 exercise produced significant blunting of d 2 counterregulatory responses to hypoglycemia. Several key d 2 counterregulatory responses were blunted to a greater extent in men than in women: glucagon (men, -105 ± 14; women, -25 ± 7 ng/liter; P < 0.0001), epinephrine (men, -2625 ± 257 pmol/liter; women, -212 ± 573; P < 0.001), norepinephrine (men, -0.50 ± 0.12 nmol/liter; women, -0 ± 0.11; P < 0.001), and muscle sympathetic nerve activity (men, -13 ± 4; women, -4 ± 4 bursts/min; P < 0.01). Cardiovascular responses (heart rate and systolic and mean arterial blood pressures) were also more blunted by antecedent exercise in men than in women. After d 1 exercise, the amount of glucose infused during d 2 hypoglycemia in men was increased 6-fold compared with that after d 1 euglycemia. This amount was significantly increased (P < 0.01) compared with the 2-fold (P < 0.01) increment in glucose infusion that was required in women after d 1 exercise. Lipolysis was unaffected by d 1 exercise in women, but was significantly blunted during d 2 hypoglycemia in men. In summary, two bouts of prolonged, moderate exercise (90 min at 50% maximum oxygen expenditure) induced a marked sexual dimorphism in key neuroendocrine (glucagon, catecholamines, and muscle sympathetic nerve activity) and metabolic (glucose kinetic, lipolysis) responses to next day hypoglycemia. - jcem.endojournals.org/cgi/content/abstract/86/8/3516

Age, Gender, and Non-modulation - A Sexual Dimorphism in Essential Hypertension 
Naomi D. L. Fisher; Claudio Ferri; Cesare Bellini; Anna Santucci; Ray Gleason; Gordon H. Williams; Norman K. Hollenberg; ; Ellen W. Seely 
From the Departments of Medicine, Harvard Medical School and Brigham and Women's Hospital, Boston, Mass, and Università La Sapienza, Rome, Italy. 
Correspondence to Naomi D.L. Fisher, Endocrine-Hypertension Division, Brigham and Women's Hospital, 221 Longwood Ave, Boston, MA 02115. E-mail ndfisher@bics.bwh.harvard.edu
Abstract The angiotensinogen gene is one of the very few related by linkage analysis to human hypertension, but the linkage has been consistently shown only among males. Moreover, polymorphisms in this gene predict an abnormal renal responsiveness to angiotensin II, a feature of non-modulation, but again, only among males. To pursue these related bridges between genetics and physiology, we evaluated the effects of sex on a second feature of non-modulation, the aldosterone response to infused angiotensin II during low sodium balance. We tested the resultant hypothesis—that non-modulation would be less frequent in women—by conducting identical protocols on 225 hypertensive inpatients (70 women, 155 men). Non-modulation was strikingly less frequent among women (26%; 95% confidence interval, 16% to 37%) than men (49%; 95% confidence interval, 40% to 57%) (P=.001). We tested the hypothesis that sex steroids play a role by comparing young, premenopausal women (<35 years) with women who were perimenopausal (45 to 55 years) and postmenopausal (>55 years). Among the youngest women, the frequency of non-modulation was only 7%, significantly less than in young men (41%, P=.02). A steady increase in non-modulation frequency accompanied advancing age in women, reaching 47% in those older than 55 years, equal to the fraction of men affected. Age influenced non-modulation frequency in men far less. We conclude that a striking sex difference underlies the non-modulation phenotype and that female sex hormones may confer protection against a genotypic predisposition in women. This "override" of genotype, manifest by a very low frequency of non-modulation in young women, may participate in their known protection against cardiovascular disease.

Childhood Sexual Abuse as a Risk Factor for Depression in Women: Psychosocial and Neurobiological Correlates 
Erica L. Weiss, M.D., James G. Longhurst, M.D. and Carolyn M. Mazure, Ph.D. 
OBJECTIVE: Depression is twice as common in women as in men, but the reason for this sexual dimorphism is unknown. This article reviews recent studies of the role of childhood sexual abuse in the subsequent development of major depressive disorder, and the biological and psychosocial mechanisms by which early stressors may contribute to adult-onset depression in women. Particular attention is paid to investigations of the long-term effects of early stress on hypothalamic-pituitary-adrenal (HPA) axis function. METHOD: Studies were identified by means of computerized and manual searches; further references were obtained from the bibliographies of reviewed articles. RESULTS: Childhood sexual abuse is associated with adult-onset depression in both men and women, and occurrence of such abuse is more common in girls than in boys. There is evidence from both animal and human studies that early stressors produce long-term dysregulation of the HPA axis similar to that seen in depressed patients and that such dysregulation results in a differential response to stressors in adulthood. In addition, it appears that the HPA axis in females may be more susceptible to stress-induced dysregulation, which might contribute to an increased vulnerability to depression in adulthood. CONCLUSIONS: Childhood sexual abuse is an important early stressor that may predispose individuals to adult-onset depression by means of dysregulation of the HPA axis. Investigation of the mechanisms mediating the relationship between childhood sexual abuse and adult-onset depression, and the study of gender differences in exposure to this and other stressors, may improve our understanding of the etiology of depressive illness in general. - ajp.psychiatryonline.org/cgi/content/abstract/156/6/816

Brain Development, XI, Sexual Dimorphism - JILL M. GOLDSTEIN, PH.D., DAVID N. KENNEDY, PH.D. and Verne S. CAVINESS, JR., M.D., D.PHIL., Boston, Mass. 
The size of the human brain is established at a young age, much earlier than motor, psychological, or cognitive maturity. Whole brain volume is at 95% of its adult size by 4 years of age. However, the brain continues to develop well through the teen years, including alteration of the relative volume of brain regions, neuronal number, synaptic connections, and neurochemistry. A number of these changes are sex specific. In the adult human brain, although the overall cerebral size is larger in men, several regions are proportionately larger in women, including the caudate nucleus, hippocampus, some prefrontal cortical areas, the superior temporal gyrus, and some white matter structures such as the anterior commissure. Regions proportionately larger in the adult male brain include the hypothalamus, stria terminalis, cerebral ventricles, and the splenium and genu of the corpus callosum. Furthermore, even for structures that reach similar volumes in men and women, the rate of structural change differs by sex. For example, the prepubertal volume of cortical gray matter is greater than its adult size, particularly in boys. In contrast, prepubertal white matter volume develops faster in girls than in boys. Sexual brain dimorphism results, in part, from hormones that affect neuronal formation and elimination and glial development. Hormones have both permanent (i.e., organizational) and acute reversible (i.e., activational) effects on the brain. The organizational actions are hardwired during critical periods of development by genomic and nongenomic events. The activational actions selectively potentiate neural circuit functions established during development. It is important to note that sexual differentiation of the brain begins during the second trimester of gestation and extends through early postnatal life to the onset of puberty. - ajp.psychiatryonline.org/cgi/content/full/156/3/352

Sexual dimorphism in humans

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