The XYY genotype

The placenta findings from an XYY abortus: a case report

INTRODUCTION

The placenta morphology from an XYY pregnancy abortus has not been reported in the medical literature. This case report consists of the first detailed documentation. The reported case is also highly unusual because the mother had two prior pregnancies with fetuses being confirmed to have Zellweger syndrome and one prior molar pregnancy.

CASE PRESENTATION

A 43-year-old Caucasian woman presented for induction of labor secondary to diagnosis of XYY chromosomes by chorionic villus sample.

CONCLUSIONS

This is the first detailed observation of placenta morphology in an XYY abortus. Although not highly specific, the observation is very unique and should prompt further investigation of karyotyping of the fetus or infant because an XYY individual may be viable and grow to adulthood. The association of an XYY abortus and prior pregnancies with Zellweger syndrome and one prior molar pregnancy is also highly notable.

Sympathetic nervous system function in XYY subjects

Initial reports of males with the XYY sex chromosome anomaly indicated that these individuals excessively exhibit impulsive, aggressive, and criminal behavior. Central nervous system (CNS) defects, including low intelligence, in certain XYY subjects may be associated with these antisocial behaviors. The sympathetic nervous system (SNS) is activated in stressful conditions of "fight or flight" upon standing up from a supine posture, with physical exercise, and with aggressive behavior. Norepinephrine (NE) is the principal neurotransmitter of the SNS, and plasma levels of NE and dopamine-beta-hydroxylase are indices of SNS function. We questioned the integrity of SNS function in XYY subjects for two reasons: (1) their inferred propensity for aggressive behavior and the association of this behavior with increased NE levels; and (2) their potential for CNS dysfunction, which could be reflected in abnormal SNS regulation by the CNS. In the current study plasma levels of NE in XYY subjects are nonsignificantly higher than in normal volunteers. Additionally, XYY patients have a normal NE half-life indicating normal SNS activity and metabolism. Thus, we are unable to document with confidence any abnormality in SNS function in these XYY subjects.

Sex differences in human mortality: the role of genetic factors

This paper reviews evidence concerning genetic factors that influence sex differences in human mortality, with attention to the interactions between genetic and environmental factors. Some widely quoted earlier conclusions, for example, that males have consistently higher fetal mortality than females, are not supported by current evidence. For example, for late fetal mortality, males had higher rates than females in earlier historical data, but not in recent data for several advanced industrial countries. This reflects a changing balance between an inherently greater female vulnerability for one major type of late fetal mortality and inherently greater male vulnerability for several other types of late fetal mortality that have declined in importance as health care has improved. Males appear to be inherently more vulnerable than females to infant mortality, although the causes of this vulnerability are poorly understood. X-linked immunoregulatory genes appear to contribute to greater female resistance to infectious diseases. Despite these apparent inherent advantages for females, in some situations females have had higher infant mortality and higher infectious disease mortality than males, apparently due to environmental disadvantages for females, such as less adequate diet and health care. Inherent sex differences in reproductive physiology and anatomy contribute to higher female mortality for breast cancer and maternal mortality. For these causes of death, as for the other categories discussed, the death rates and thus the contributions to sex differences in total mortality vary considerably depending on environmental conditions. Several hypothesized contributions of sex hormones to sex differences in mortality are at present controversial due to contradictions and limitations in the available data. There may be effects of male sex hormones on sex differences in behavior which contribute to males' higher death rates for accidents and other violent causes. Women's endogenous sex hormones may reduce women's risk of ischemic heart disease. For both violent deaths and ischemic heart disease it appears that any genetic contributions to sex differences in mortality are strongly reinforced by the cultural influences that foster more risky behavior in males, including more use of weapons, employment in hazardous occupations, heavy alcohol consumption and cigarette smoking. It appears that these cultural influences on sex differences in behavior are widespread cross-culturally in part because of the effects of inherent sex differences in reproductive functions on the cultural evolution of sex roles. These examples illustrate the complexity and importance of interactions between genetic and environmental factors in determining sex differences in human mortality.

Postnatal gonadal steroid effects on human behavior

Gonadal steroid hormones, active during fetal life, continue after the birth of a fetus to influence the central nervous system and affect behavior. The characteristically different circulating concentrations of male and female steroid hormones in men and women appear to be partial determinants of certain sexually dimorphic behaviors, interacting in a complex way with psychological and sociocultural factors as well as with other biological factors. This interaction is highlighted in research on testosterone and aggression in men, mood and the menstrual cycle in women, and pubertal sex role reversal in pseudohermaphrodites.

Abnormal cerebral cortical convolutions in an XYY fetus

Because of maternal disease a pregnancy was electively terminated at 21 weeks of fetal gestation. At autopsy the fetus showed an abnormal pattern of cerebral cortical convolutions involving the frontal lobes. Karyotpic analysis revealed an XYY sec chromosome constitution. This observation, if confirmed in other XYY cases, raises the possibility that a developmental abnormality of the cerebral cortex may be involved in the higher-than-normal risk for behavioral disability exhibited by men with this genotype.