Are there any relationships between latent Toxoplasma gondii infection, testosterone evelatin, and risk of autism spectrum disorder?
Abdoli A, Dalimi A.
Frontiers in Behavioral Neuroscience 2014; 8
Potential solutions to problems posed by the offspring sex ratios of people with parasitic and viral infections
James, W. H.
Folia Parasitologica 2010; 57:114-120
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I have hypothesized that mammalian offspring sex ratios (proportions male at birth) are partially controlled by the hormone levels of both parents around the time of conception. Recently data have been published (privately) which impugn suggestions of mine (based on that hypothesis) relating to the offspring sex ratios of people who are carriers of hepatitis B virus; and (publicly) to hormone profiles of women who are infected with the protozoan parasite Toxoplasma gondii. Here these data are reviewed in the light of data on offspring sex ratios of people infected with hepatitis C, and cytomegalovirus and T gondii; and of mice with T gondii and the trichostrongyline nematode Heligmosomoides polygyrus. Three proposals are made viz: I. Women infected with T gondii may have high oestrogen levels. This would potentially explain reports of their high offspring sex ratios, long gestations and (perhaps) behavioural traits. 2. Some of these infective organisms may 'prefer' a particular endocrine environment in their host (in the sense that it facilitates replication or transmission or both). 3. Some of these organisms apparently cause changes in that endocrine environment as a consequence of their presence. If both the latter two proposals were correct, it could explain recent puzzling data on the offspring sex ratios of hepatitis B carriers. And if this solution turns out to be correct, it would suggest new endocrine means of combating hepatitis B infection.
Sex-dependent toxoplasmosis-associated differences in testosterone concentration in humans
Flegr, J., Lindová, J., Kodym, P.
Parasitology 2008; 135: 427-431
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Several lines of indirect evidence suggest that subjects with latent infection of the coccidian parasite Toxoplasma gondii have a higher concentration of testosterone than uninfected controls. Here, we searched for direct evidence of latent toxoplasmosis-associated differences in testosterone concentration among a Population of 174 female and 91 male students screened for Toxoplasma infection. We have found Toxoplasma-infected men to have a higher concentration of testosterone and Toxoplasma -infected women to have a lower concentration of testosterone than Toxoplasma -free controls. The opposite direction of the testosterone shift in men compared to women can explain the observed gender specificity of behavioural shifts in Toxoplasma- infected subjects.
Brief communication: Latent toxoplasmosis and salivary testosterone concentration-important confounding factors in second to fourth digit ratio studies
Flegr, J., Lindova, J., Pivonkova, V., Havlicek, J.
American Journal of Physical Anthropology 2008; 137: 479-484
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A sexually dimorphic characteristic, the second to fourth digit ratio (2D:4D ratio), has been shown to reflect the prenatal concentration of sex steroid hormones and to correlate with many personality, physiological, and life history traits. The correlations are usually stronger for the right than the left hand. Most studies have shown that the 2D:4D ratio does not vary with age or postnatal concentration of sex steroid hormones. Recently, a strong association between left hand 2D:4D ratio and infection with a common human parasite Toxoplasma has been reported. We hypothesized that the confounding effect of Toxoplasma infection on left hand 2D:4D ratio could be responsible for the stronger association between different traits and right hand rather than left hand 2D:4D ratio. This confounding effect of toxoplasmosis could also be responsible for the difficulty in finding an association between 2D:4D ratio and age or postnatal steroid hormone concentration. To test this hypothesis, we analyzed the association between sex and age and 2D:4D ratio in a population of 194 female and 106 male students with and without controlling for the confounding variables of Toxoplasma infection and testosterone concentration. Our results showed that the relationship between age and sex and 2D:4D ratio increased sharply when Toxoplasma infection and testosterone concentration were controlled. These results suggest that left hand 2D:4D ratio is more susceptible to postnatal influences and that the confounding factors of Toxoplasma infection, testosterone concentration and possibly also age, should be controlled in future 2D:4D ratio studies. Because of a stronger 2D:4D dimorphism in Toxoplasma-infected than Toxoplasma-free subjects, we predict that 2D:4D ratio dimorphism as well as right hand/left hand 2D:4D ratio dimorphism will be higher in countries with a high prevalence of Toxoplasma infection than in those with a low prevalence. Am J Phys Anthropol 137:479-484, 2008. (C) 2008 Wiley-Liss, Inc.