Parabens are classified as endocrine disrupting compounds (EDCs), capable of interfering with the normal functioning of the thyroid, affecting the proper regulation of the biosynthesis of thyroid hormones (TH) which is controlled by hypothalamic-pituitary-thyroid axis (HPT). Given the crucial role of these hormones in health and the growing evidence of diseases related to thyroid dysfunction, this review looks at the effects of paraben exposure on the thyroid. In this study, we considered research carried out in vitro, in vivo, and epidemiological studies published between 1951 and 2023, which demonstrated an association between exposure to parabens and dysfunctions of the HPT axis. In humans, exposure to parabens appears to increase thyroid-stimulating hormone (TSH) levels, while in rodents, exposure decreases TSH levels. The effects on HT levels are also poorly described, as well as peripheral metabolism. Regardless, recent studies have shown different actions between different subtypes of parabens on the HPT axis, which allows us to speculate that the mechanism of action of these parabens is different. Furthermore, studies of exposure to parabens are more evident in women than in men. Therefore, future studies are needed to clarify the effects of exposure to parabens and their mechanisms of action on this axis.

Endocrine disruptor compounds are exogenous agents able to interfere with a gland function, exerting their action across different functional passages, from the synthesis to the metabolism and binding to receptors of the hormone produced. Several issues such as different levels and time of exposure and different action across different ages as well as gender, make the study of endocrine disruptors still a challenge. Thyroid is very sensitive to the action of disruptors, and considering the importance of a correct thyroid function for physical and cognitive functioning, addressing this topic should be considered a priority. In this review we examined the most recent studies, many of them concentrating on maternal and child exposure, conducted to assess the impact of industrial chemicals which showed an impact on thyroid function. So far, the number of studies conducted on that topic is not sufficient to provide solid conclusions and lead to homogeneous guidelines. The lack of uniformity is certainly due to differences in areas and populations examined, the different conditions of exposures and the remarkable inter-subject variability. Nonetheless, the European Commission for Health and Food Safety is implementing recommendations to ensure that substances identified as endocrine disruptors will be withdrawn from the market.

Abstract. Introduction: BMD study gives partial information on bone health in patients with TSH suppression therapy due to Differentiated Thyroid Cancer (DTC). TBS, a new parameter of bone microarchitecture is propose for bone quality study. This study analyze their long-term use in patients with DTC. Methods: BMD was measured by DXA and TBS with iNsigth software in 145 postmenopausal DTC patients. Vertebral Fractures (VFs) with a semi-quantitative x-ray method. Results: BMD at the end study was not different from initial. TBS decreased from 1.35±0.1 to 1.27±0.1 (p=0.002). PTH, Osteocalcin, and BAP were increased, suggesting increased bone remodeling. There was an increase in osteoporosis and osteopenia (40.6% and 16.5% to 46.6% and 18.6%); 31% had partially degraded and 15.1% degraded TBS changed to 48,9% and 24,8% at the end study. VFs in 30 patients, was not different in age, BMI, calcium and alcohol ingestion, smoking, radioiodine, or thyroid parameters vs. without VFs. Odds ratio for VFs increased with osteopenia (OR 2.63). Combination of TBS plus TBS did not improve discrimination. Conclusions: TBS was lowered while BMD did not differ. Percentage of osteoporosis and osteopenia and of partially degraded and degraded TBS was higher at the end study. Predominant discordance rate was found in partially degraded microarchitecture, in which the proportion of osteopenia was higher than normal or osteoporotic patients. AUC of TBS plus BMD did not improve discrimination. TBS, radioactive iodine, and sedentary lifestyle were the main differential data for patients with DTC and VFs.

Anemia and thyroid disorders are global health issues that affect all ages but are more apparent in women. In this case, some serological components responsible for IDA and TSH disorders in women have been found actively regulated through a complex steroidal-calcitriol mediated pathway. This research has been investigated the correlation between Calcitriol and the serological components responsible for IDA and TSH disorders in childbearing and non-child-bearing women of different health conditions. Experimental sampling from 452 women suffering from both IDA and TSH disorders were taken, aged between 0 and 70 years. Serological parameters, such as iron, total iron-binding capacity and ferritin, were assessed for IDA profiling, whereas thyroid-stimulating hormone and free thyroxin were for TSH profiling based on the individual’s serum calcitriol status. The resulted serological data were interpreted using sophisticated computer programming language and algorithms for quantitative biochemical analysis. The study resulted in a significant correlation between FT4 and Calcitriol (P<0.0001) for all age groups. TSH also showed strong interactions with the fluctuation of calcitriol level (P<0.0001), except for the children aged below 10 years (P<0.063). The iron, TIBC, TSH, and FT4 showed phenomenal regulation with the steroidal-calcitriol concentration for congenital patients. Unlike the others, ferritin has a substantial connection with Calcitriol (P<0.0064) fluctuation in the serum. To ratify, the concentrations of TSH, FT4, iron, TIBC, and ferritin were found to be significantly interconnected in terms of serum calcitriol level in women suffering from IDA and TSH disorders simultaneously. To understand the accuracy and efficacy of the Calcitriol in IDA and TSH disorders, some other inflammatory markers and parathyroid hormone analysis are need in future studies, besides a large number of samples.

Mexico shows a high birth prevalence of congenital hypothyroidism (CH) due to thyroid dysgenesis (TD). PAX8 defects underlie only 1% of these cases and NKX2-1 does not seem to be involved. Here, we analyzed other TD-related genes in 128 non-related Mexican patients (females 77.3%; 6 months to 16.6 years) with non-syndromic CH-TD diagnosis established by clinical evaluation, thyroid hormone serum profiling, and scintigraphy (74%) or ultrasonography (26%). We performed Sanger sequencing of FOXE1, NKX2-5, and TSHR and evaluated copy number variations (CNVs) in TSHR, FOXE1, PAX8, and NKX2-1 by multiplex ligation-dependent probe amplification. Odds ratios for TD risk were explored for FOXE1 polyalanine stretches [polyAla-rs71369530] in cases and controls (N=116). Five rare missense changes cataloged as benign (NKX2-5:p.(Ala119Ser)-rs137852684), of unknown significance (FOXE1:p.(Ala335Gly)-rs543372757; TSHR:p.(Asp118Asn)-rs1414102266), and likely pathogenic (FOXE1:p.(Gly124Arg)-rs774035532; TSHR:p.(Trp422Arg)-rs746029360) accounted for 1.5% (N=2/128) of clinically relevant genotypes (supported in part by protein modeling) in CH-TD. No CNVs were identified, nor did polyAla &gt;14 alanines in FOXE1 significantly protect against TD. The present and previously published data collectively show that small clinically relevant germline variants in PAX8, FOXE1, and TSHR are found in only a very small proportion (2.5%) of isolated CH-TD Mexican patients.