Based on limited published evidence, MT1HL1 encodes a metallothionein with high cysteine content that binds heavy metals and undergoes transcriptional regulation by heavy metals and glucocorticoids. The protein localizes to the cytoplasm and nucleus, functioning in metal ion homeostasis through detoxification of copper and zinc, and cellular responses to cadmium, copper, and zinc ions. MT1HL1 was identified as a critical gene associated with lead toxicity in peripheral blood mononuclear cells, clustering with other metallothionein family members in metal ion binding and absorption pathways 1.