Environmental Endocrinology: Parabens Hazardous Effects on Hypothalamic-Pituitary-Thyroid Axis

Area of Science:

• Endocrinology and Toxicology
• Environmental Health Sciences

Background:

• Parabens are common preservatives classified as endocrine-disrupting chemicals (EDCs).
• Thyroid hormones (THs) are vital for metabolic regulation, controlled by the hypothalamic-pituitary-thyroid (HPT) axis.
• Thyroid dysfunction is linked to various health issues, highlighting the importance of understanding environmental impacts.

Purpose of the Study:

• To review the effects of paraben exposure on thyroid function and the HPT axis.
• To synthesize findings from in vitro, in vivo, and epidemiological studies.
• To identify knowledge gaps and suggest future research directions.

Main Methods:

• Comprehensive literature search of studies published between 1951 and 2023.
• Inclusion of in vitro, in vivo, and human epidemiological research.
• Analysis of studies investigating paraben associations with HPT axis dysfunction.

Main Results:

• Paraben exposure is associated with HPT axis dysfunction.
• Human studies show increased thyroid-stimulating hormone (TSH) levels, while rodent studies indicate decreased TSH.
• Effects on TH levels and peripheral metabolism remain poorly understood; different paraben subtypes may have distinct mechanisms.

Conclusions:

• Paraben exposure poses a risk to thyroid function and HPT axis regulation.
• Discrepancies in TSH responses between humans and rodents warrant further investigation.
• More research is needed to elucidate paraben mechanisms and sex-specific effects, particularly in women.