Suchergebnisse

Abstract

Objectives
This study was performed to review epidemiological evidence related to Arsenic (As) effects on the thyroid function by focusing on the serum thyroid hormone concentration.


Content
As, one of the main pollutants, has been recognized as an endocrine-disrupting agent that may affect the function of thyroid as shown by experimental studies.


Summary
This systematic study indicates the association between As exposure and thyroid dysfunction. The studies have shown an association between serum and urine concentration of arsenic and thyroid dysfunction. Most of them reported the association between increase in the serum or urine As levels and decrease in the triiodothyronine (T3) and thyroxine (T4), and also elevation in the thyrotropic hormone (TSH) levels.


Outlook
Our findings related to the effects of As on the function of thyroid in humans are still limited and future studies should be done to address this question.

Abstract
Organophosphate (OP) pesticides, including chlorpyrifos (CPF), can alter metabolic hemostasis. The current systematic study investigated blood glucose, lipid profiles, and body weight alterations in rodents and fish exposed to CPF. The systematic review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) Guidelines, querying online databases, including Web of Science, PubMed, and Scopus and also search engine including Google Scholar, through January 2021. Studies on rodent and fish exposed to CPF assessing metabolic functions were selected. All studies were in the English language, with other languages being excluded from the review. Two investigators independently assessed each of the articles. The first author's name, publication date, animal model, age, sample size, gender, dose, duration, and route of exposure and outcomes were extracted from each publication. The present review summarizes findings from 61 publications on glycemic, lipid profile, insulin, and body weight changes in rodents and fish exposed to CPF exposure. Most of the studies reported hyperglycemia, hyperlipidemia, and decreased insulin levels and body weight following exposure to CPF. Additionally, we confirmed that the CPF-induced metabolic alterations were both dose- and time-dependent. Our findings support an association between CPF exposure and metabolic diseases. However, more studies are needed to identify the metabolic-disrupting effects of CPF and their underlying mechanisms.

Abstract

Objective
Numerous evidence indicates the association between polychlorinated biphenyls (PCBs), an endocrine disrupter, with thyroid hormone disruption, contradictory findings also exist. Herein, we tried to address this question by performing a scoping review.


Content
The search was performed on PubMed, Scopus, Web of Science, and Google Scholar databases from 2010 onwards. Animal studies on PCBs' effect on thyroid function were searched. The SYRCLE's RoB scale assessed the risk of bias. I2 and Q tests are used for investigating heterogeneity. A random-effects model with the pooled standard means difference (SMD) and 95 % confidence interval (CI) was performed for the TSH, TT4, TT3, and FT4 outcomes using Comprehensive Meta-Analyses (CMA) Software version 3. Also, we conducted subgroup analyses based on the different types of PCB. The initial search identified 1,279 publications from the main databases 26 of them fulfilled our eligibility criteria for the study, and then five studies among selected studies had sufficient data for analysis. Meta-analysis of data revealed that Aroclor 1260 (SDM: −0.47, 95 % CI: −0.92, −0.01, p=0.044) and PCB 126 (SDM: 0.17, 95 % CI: −0.40, 0.75, p=0.559) significantly increased TSH concentration in the exposed groups vs. the control groups. Related to the effects of PCBs on the TT4, our findings indicated a significant reduction the TT4 concentration of animals exposed to Aroclor 1260 (SDM: −5.62, 95 % CI: −8.30, −2.94, p=0.0001), PCB 118 (SDM: −6.24, 95 % CI: −7.76, −4.72, p=0.0001), PCB 126 (SDM: −1.81, 95 % CI: −2.90, −0.71, p=0.001), and PCB 153 (SDM: −1.32, 95 % CI: −2.29, −0.35, p=0.007) vs. the controls. Our meta-analysis indicated a significant increase in TT3 concentration following exposure to PCB 118 and PCB 153 (SDM: −0.89, 95 % CI: −1.36, −0.42, p=0.0001, and SDM: −1.45, 95 % CI: −2.15, −0.75, p=0.0001, respectively). Aroclor 1254 and PCB 126 significantly decreased TT3 concentration (SDM: 1.25, 95 % CI: 0.29, 2.21, p=0.01 and SDM: 3.33, 95 % CI: 2.49, 4.18, p=0.0001, respectively). PCB 126 significantly decreased FT4 in the exposed groups vs. the control groups (SDM: −7.80, 95 % CI: −11.51, −5.35, p=0.0001).


Summary
Our findings showed an association between PCBs exposure and hypothyroidism in rodents, fish, and chicken embryos.


Outlook
Regarding to the most evidence of hypothyroidism effects of PCBs in animal species, it is necessary to consider large cohort studies to address the association between PCBs exposure and thyroid function impairment in humans.