Thyroid gland endocrine disruption

Amphibians. Amphibians are highly susceptible to endocrine disruption during development of the larval form and during metamorphosis. The action of metamorphosis is triggered and controlled by the thyroid gland via an increase in triiodothyronine and a decrease in thyroxine, and differs greatly between oviparous and viviparous species. Experimentally, it has been shown that disruption during this sensitive period can lead to malformations and adverse impacts on immune and reproductive functions. 

As an endocrine disrupter, 2,4-D causes suppression of thyroid hormone levels, increases thyroid gland mass, and decreases weight of the ovaries and testes [33]. 2,4-D causes slight decreases in testosterone release and significant increases in estrogen release from testicular cells [34]. Male farm sprayers exposed to 2,4-D had lower sperm counts and more spermatic abnormalities compared to men who were not exposed to this chemical [35]. 

All OCPs are polytropic, parenchymatous poisons, afflicting the central nervous system, liver, kidneys, the heart muscle, the stomach and intestines, and the endocrine system (mostly the adrenal glands, thyroid, and ovaries). Morphological changes in warm-blooded creatures poisoned by OCPs vary from insignificant disruptions in circulation and reversible dystrophy to focal necroses these effects depend on the organism, the dose of OCP, how long the OCP remains active, as well as on other factors [9, 39, 40, A47, A79]. 

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