Given the central role that hormones play in guiding the development of the reproductive system and then in controlling its activities once developed, it is not surprising that a major focus of endocrine disruption research has been on reproductive health. Our Stolen Future reviews many studies, especially experimental work with laboratory animals, that document endocrine disruption of the reproductive system. These include reductions in fertility, alterations in sexual behavior, deformations of the reproductive tract and reproductive diseases.

Research reported since the publication of Our Stolen Future has continued to explore these themes. The animal literature has emphasized mechanistic understanding of how endocrine disruptors work, with new revelations on the exquisite sensitivity of the developing fetus to chemical hijacking. Research on mixtures showing fetal loss in mice even to very low levels of herbicides suggests that current regulatory toxicology is probably failing to protect public health.

The research on people has attempted to resolve several controversies (for example, whether sperm count is declining, and if so, why?), to determine whether several reproductive system cancers (especially breast cancer) are linked to organochlorine contaminants, and to establish trends in reproductive tract disorders in men and women, for example, hypospadias and endometriosis. Analysis suggests that sperm declines, hypospadias, cryptorchidism and testicular cancer are different manifestations of the same syndrome, testicular dysgenesis syndrome.

Now some scientists have even begun to question whether the "demographic transition" ... the decline in birth rates associated with improving economic conditions... may have an involuntary component linked to contamination-impaired reproduction. The traditional explanation is that as economies improve and childhood survival increases, women make voluntary choices to have smaller family sizes. More...

Concerns have also been raised about links between cryptorchidism in people (affecting about 3% of newborn males) and in utero exposure to organochlorines. Research is firming up those links and also revealing their molecular basis. More...

New issues have arisen, also, which based on animal studies may involve endocrine disruption, including reductions in the age of puberty and changes in the human sex ratio. A recent study even suggests eating contaminated fish may impair a woman's ability to conceive children.

Another new study shows that women within a few miles of where pesticides are used on agricultural fields have an increased risk of having their fetus dying during pregnancy.

Experimental studies in the laboratory have proven crucial to revealing important impacts, identifying human health endpoints that should be examined, clarifying mechanisms, and exploring questions about sensitivity to low doses and to mixtures. They have also been essential to documenting different types of endocrine disruption and to establishing which compounds have hormonal effects.

Some points of entry:

• on non-estrogen effects, such as antiandrogen
• on low doses
• on mixtures

Recent relevant results:

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