The thyroid has been shown to be a target organ of environmental chemicals, specifically endocrine disrupting
contaminants. Reptiles are particularly suitable as contaminant biomonitors, due to their persistence in a variety of
habitats, wide geographic distribution, longevity, and, in many cases, site fidelity. Nonylphenol, an estrogenic-like
compound, can induce vitellogenin synthesis in males and immature reptilian species, but little is known about its effects
on thyroid hormones balance. The present study evaluated the potential effects of an acute exposure to nonylphenol (i.p.
injected) on the thyroid of the lizard Podarcis sicula.
Nonylphenol induced a significant decrease of T4 and T3 plasma levels, in agreement with the decrease of the epithelial
cell height; the nuclei of the thyroid cells were small and elongated, with dense chromatin and a greatly reduced
cytoplasm. The colloid was retracted with few reabsorption vacuoles. Moreover, nonylphenol administration significantly
inhibited plasma thyroid-stimulating hormone levels, thereby altering the thyroid function.
This study highlights how the structural and functional disruption of the thyroid gland in non-target organisms as the
lizard might also have an environmental aetiology. In conclusion, nonylphenol was suspected to inhibit the thyroid
hormones balance, suggesting the thyroid should be included among the other endocrine glands, susceptible to endocrine