Cadmium exposure and thyroid hormone disruption: a systematic review and meta-analysis

Area of Science:

• Environmental Health
• Endocrinology
• Toxicology

Background:

• Cadmium (Cd) is a toxic heavy metal with widespread environmental exposure.
• Thyroid hormones are crucial for metabolic regulation and development.
• Disruption of thyroid function by environmental toxicants is a growing public health concern.

Purpose of the Study:

• To systematically review and meta-analyze the association between cadmium exposure and thyroid hormone disruption.
• To evaluate the impact of cadmium on thyroid-stimulating hormone (TSH), free thyroxine (FT4), total triiodothyronine (TT3), and thyroid autoimmunity.

Main Methods:

• A comprehensive literature search was conducted in PubMed, Embase, Cochrane Library, and Scopus up to December 14, 2022.
• Included studies assessed the relationship between blood cadmium (BCd) or urine cadmium (UCd) and thyroid function or autoimmunity markers.
• Meta-analysis was performed on data from 12 cross-sectional studies.

Main Results:

• Cadmium exposure showed a neutral association with TSH, FT4, and thyroid autoimmunity.
• A significant positive association was observed between cadmium exposure and total triiodothyronine (TT3) levels.
• This positive association with TT3 was consistent across blood and urine cadmium subgroup analyses.

Conclusions:

• Cadmium exposure may not significantly disrupt TSH, FT4, or thyroid autoimmunity.
• Cadmium exposure is associated with elevated total triiodothyronine (TT3) levels.
• Further research is warranted to elucidate the mechanisms underlying cadmium's effect on TT3.