en Public Health Public Health پژوهشي Original Article <p><span style="font-size:14px;"><span style="font-family: times new roman;"><strong>Background;</strong> In recent years, nanoparticles have been increasingly used in industries. However, there is a serious lack of information concerning their impact on human health and the environment. This study was investigated the effect of MoO₃ NPs on thyroid hormones in female rats.<br> <strong>Methods; </strong>In this study, 21 female Wistar rats were selected and divided into three groups of untreated control, sham and treatment group with seven rats in each group. During 28 days the sham group received normal saline and treatment group received 5 mg/kg (MoO₃ NPs) in normal saline. After the final injection, blood samples were collected and serum levels of total thyroxine (T₄), triiodothyronine (T₃), and thyroid-stimulating hormone (TSH) were measured and groups were compared together.</span></span><br> <span style="font-size:14px;"><span style="font-family: times new roman;"><strong>Results; </strong>The results showed that the serum levels of T₄ decreased significantly in group of 5 mg (MoO₃ NPs) in comparison with the control group (<em>p&nbsp;</em>< 0.05). However, there was insignificant difference observed in T₃ levels when compared with the control group (<em>p</em>>0.05). The serum levels of TSH increased significantly in group of 5 mg/kg (MoO₃ NPs) when compared with the both groups of sham and control (<em>p</em><0.05).</span></span><br> <span style="font-size:14px;"><span style="font-family: times new roman;"><strong>Conclusion; </strong>The results showed that MoO₃ NPs exposure induces the risk of thyroid dysfunction.</span></span></p> Molybdenum trioxide nanoparticles, Rat, Thyroid hormones 189 195 http://jhehp.zums.ac.ir/browse.php?a_code=A-10-67-1&slc_lang=en&sid=1 Fardin Assadi assadi_fardin@yahoo.com 10031947532846009343 10031947532846009343 No Department of Pediatric, Mousavi Hospital, Zanjan University of Medical Sciences, Zanjan, Iran. Hamidreza Amirmoghaddami baharlab@gmail.com 10031947532846009344 10031947532846009344 No Vali-e-Asr Hospital, Zanjan University of Medical Sciences, Zanjan, Iran. Mojghan Shamseddin yassamin_1@zums.ac.ir 10031947532846009345 10031947532846009345 No Department of Pathology, School of Medicine, ZUMS, Zanjan, Iran. Keivan Nedaeei Nedaee.k@gmail.com 10031947532846009346 10031947532846009346 No Department of Medical Biotechnology and Nanotechnology, School of Medicine, Zanjan University of Medical Sciences, Zanjan, Iran. Azam Heidari a.c.heidari@gmail.com 10031947532846009347 10031947532846009347 Yes Department of Molecular Medicine and Genetics, School of Medicine, Zanjan University of Medical Sciences, Zanjan, Iran.