OctylPhenol (OP) Alone and in Combination with NonylPhenol (NP) Alters the Structure and the Function of Thyroid Gland of the Lizard Podarcis siculus

Abstract

Different environmental contaminants disturb the thyroid system at many levels. AlkylPhenols (APs), by-products of microbial degradation of AlkylPhenol Polyethoxylates (APEOs), constitute an important class of Endocrine Disrupting Chemicals (EDCs), the two most often used environmental APs being 4-nonylphenol (4-NP) and 4-tert-octylphenol (4-t-OP). The purpose of the present study was to investigate the effects on the thyroid gland of the bioindicator Podarcis siculus of OP alone and in combination with NP. We used radioimmunoassay to determine their effects on plasma 3,3′,5-triiodo-L-thyronine (T3), 3,3′,5,5′-L-thyroxine (T4), thyroid-stimulating hormone (TSH), and thyrotropin-releasing hormone (TRH) levels in adult male lizards. We also investigated the impacts of AP treatments on hepatic 5′ORD (type II) deiodinase and hepatic content of T3 and T4. After OP and OP + NP administration, TRH levels increased, whereas TSH, T3, and T4 levels decreased. Lizards treated with OP and OP + NP had a higher concentration of T3 in the liver and 5′ORD (type II) activity, whereas T4 concentrations were lower than that observed in the control group. Moreover, histological examination showed that the volume of the thyroid follicles became smaller in treated lizards suggesting that that thyroid follicular epithelial cells were not functionally active following treatment. This data collectively suggest a severe interference with hypothalamus–pituitary–thyroid axis and a systemic imbalance of thyroid hormones. Graphic Abstract

Thyroid and reproduction in amphibians and reptiles

“…As reported for amphibians, normal functioning of the HPT axis and/or the HPG axis can be disrupted in reptiles by anthropogenic chemicals such as pesticides, fertilizers, pharmaceuticals, and industrial chemicals (Boggs et al, 2011;Milnes, 2024;Sciarrillo et al, 2021). Alterations in either the HPT or HPG axes would have serious implications for effective reproduction, especially in the face of climate changes and environmental pollution.…”

Alkyphenol Exposure Alters Steroidogenesis in Male Lizard Podarcis siculus

“…NP and OP were dissolved in 50 µL of corn oil used, respectively, at concentrations of 0.172 µg and 0.161 µg based on previously studies [44][45][46][47] and administered through intraperitoneal injections every 2 days.…”

Combined Effects of Different Endocrine-Disrupting Chemicals (EDCs) on Prostate Gland

“…Although risk assessments have been historically conducted on a chemical-by-chemical basis, regulatory agencies are beginning to consider the cumulative risk of chemicals. Moreover, it is now well known that humans [ 97 , 98 , 99 , 100 , 101 , 102 , 103 ], fish [ 11 , 104 , 105 , 106 , 107 , 108 ], and wildlife [ 109 , 110 , 111 , 112 ] are continuously exposed to multiple contaminants [ 103 , 113 ]. In this view, it is essential to study the effect of combined multicomponent mixtures on prostate diseases rather than individual substances in order to highlight the involvement of multiple compounds acting simultaneously in prostate pathologies [ 78 , 114 , 115 ].…”

“…Many chemicals with anti-androgenic actions have been shown to act together in combination, producing effects at doses that individually are not associated with any observable responses [ 103 , 127 , 128 , 129 , 130 , 131 , 132 ]. Anti-androgens are compounds that can act on male sexual development but with different modes of action, such as the inhibition of androgen hormone biosynthesis or blocking of receptor-mediated signaling [ 112 , 133 , 134 ]. Chemicals with estrogenic action can also disturb the development of male reproductive organs [ 132 , 135 , 136 , 137 , 138 , 139 , 140 ], but little is known about the effects of mixtures of estrogenic and anti-androgenic chemicals [ 132 ].…”