The possible involvement of lipid peroxidation (LPO) in the lead (Pb) and cadmium (Cd) induced thyroid dysfunction with special reference to type‐I iodothyronine 5′‐monodeiodinase (5′‐D) activity was studied in rat liver homogenate. Peroxidative reactions involving membrane components were found to be markedly stimulated by chronic administration of Pb and Cd in rats. Metal induced inhibition in 5′‐D activity was also observed. Since LPO is primarily an outcome of free radical generation, we suggest metal induced free radical mediated inhibition of 5′‐D activity in rat liver homogenate. In addition, serum triiodothyronine (T3) and thyroxine (T4) concentrations were also decreased by metals.

Pigmented lesions are commonly found in the oral cavity. Oral pigmentations may be physiological or pathological in nature. It may represent as a localized anomaly of limited significance or the presentation of potentially life threatening multisystem disease. Oral pigmentation has a multifactorial etiology. Most of the oral pigmentations are physiologic. Evaluation of a patient with pigmented lesions should include a full medical and dental history, extraoral and intraoral examinations. In this article, we report a case of extensive physiologic pigmentation of the oral cavity in a 12 year old female patient, posing a diagnostic challenge.

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