Our Stolen Futurea book by Theo Colborn, Dianne Dumanoski, and John Peterson Myers


  Sower, SA, KL Reed and KJ Babbitt. 2000. Limb Malformations and Abnormal Sex Hormone Concentrations in Frogs. Environmental Health Perspectives 108:1085-1090.



In what may represent a breathrough in the scientific exploration of frog deformities, Sower et al. report that deformed individuals of two species of wild frogs in New Hampshire have abnormal concentrations of sex hormones compared to normal individuals from the same region. These results are consistent with the hypothesis that endocrine disruption is involved in the genesis of frog deformities. The hormonal disruptions reported by Sower et al. would not be expected to be associated with deformities caused by parasites or predation.

Research on frog deformities to date has largely emphasized two approaches: basic surveys to establish rates of deformities in different sites and species, and efforts to identify factors present at those sites which might cause deformities.

This paper opens a new front on research, asking about the hormonal condition of deformed frogs. It is analogous to the pathbreaking work by Dr. Louis Guillette on alligators in Lake Apopka, Florida, with miniature penises: much of Guillette's early work focused on establishing that hormones in these alligators were wildly out of balance, which then led to further experimental studies establishing that the imbalances were caused by a cocktail of contaminants present in the lake.

Sower et al. captured normal and deformed frogs of two species (green frogs and bull frogs) from locations across central and southern New Hampshire. They found deformed frogs at 81% of sites where they caught 50 or more frogs. The percentage of frogs malformed varied from 0 to 9.3% at a given site, while overall the total malformation rate was 3.9%... 4.3% for bullfrogs and 2.4% for green frogs. [These rates are low compared to collections reported in other places, for example Minnesota and Quebec.]

Sower et al. examined two patterns of hormonal disruption in the frogs: levels of gonadotropin-release hormone in the brain and the amounts of androgens produced by testes and ovaries in an in vitro assay.

The results are clear-cut: deformed frogs have lower concentrations of gonadotropin-release hormones in the brain, and both male and female gonads of deformed animals produce reduced androgens

  These two graphs (adapted from Sower et al.) compare normal with deformed frogs in two measurements of hormone function: the production of gonadotrophin-releasing hormone in the brain, and production of androgens by the gonads. Both comparisons reveal strong differences between normal and deformed animals.  

According to the authors, "Although chemical mechanisms cannot be ruled out ... [these results] suggest that parasite infestation is not the causal agent in our study.

"The significant decrease in GnRH (brain gonadotropin-releasing hormone) correlated with depressed androgen concentrations and lack of proper testicular morphology in malformed frogs provides evidence that development of the neuroendocrine system may have been disrupted during early frog development."







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