may detect sex hormones in the system. the female sex hormone 17-β-estradiol has been shown to regulate the level of immunological response, while some male androgens such as testosterone seem to suppress the stress response to infection. other androgens, however, such as dhea, increase immune response. as in females, the male sex hormones seem to have more control of the immune system during puberty and post-puberty than during the rest of a male's adult life. physical changes during puberty such as thymic involution also affect immunological response. ecoimmunology and behavioural immunity main articles: ecoimmunology and behavioral immune system ecoimmunology, or ecological immunology, explores the relationship between the immune system of an organism and its social, biotic and abiotic environment. more recent ecoimmunological research has focused on host pathogen defences traditionally considered "non-immunological", such as pathogen avoidance, self-medication, symbiont-mediated defenses, and fecundity trade-offs. behavioural immunity, a phrase coined by mark schaller, specifically refers to psychological pathogen avoidance drivers, such as disgust aroused by stimuli encountered around pathogen-infected individuals, such as the smell of vomit. more broadly, "behavioural" ecological immunity has been demonstrated in multiple species. for example, the monarch butterfly often lays its eggs on certain toxic milkweed species when infected with parasites. these toxins reduce parasite growth in the offspring of the infected monarch. however, when uninfected monarch butterflies are forced to feed only on these toxic plants, they suffer a fitness cost as reduced lifespan relative to other uninfected monarch butterflies. this indicates that laying eggs on toxic plants is a costly behaviour in monarchs which has probably evolved to reduce the severity of parasite infection. symbiont-mediated defenses are also heritable across host generations, despite a non-genetic direct basis for the transmission. aphids, for example, rely on several different symbionts for defense from key parasites, and can vertically transmit their symbionts from parent to offspring. therefore, a symbiont that successfully confers protection from a parasite is more likely to be passed to the host offspring, allowing coevolution with parasites attacking the host in a way similar to traditional immunity. the preserved immune tissues of extinct species, such as the thylacine (thylacine cynocephalus) can also provide insights into their biology. cancer immunology main article: cancer immunology the study of the interaction of the immune system with cancer cells can lead to diagnostic tests and therapies with which to find and fight cancer. the immunology concerned with physiological reaction characteristic of the immune state. reproductive immunology main article: reproductive immunology this area of the immunology is devoted to the study of immunological aspects of the reproductive process including fetus acceptance. the term has also been used by fertility clinics to address fertility problems, recurrent miscarriages, premature deliveries and dangerous complications such as pre-eclampsia.