Betel leaf (paan) chewing: an unusual cause of refractory hypothyroidism in levothyroxine-treated patient

The habit of chewing betel leaf, or "paan", is prevalent in different parts of India. Betel leaves, areca nut, and lime are common ingredients of paan. Preclinical studies have demonstrated that betel leaf and areca nut affect thyroid function. Lime, due to its high calcium content, adsorbs levothyroxine (LT4) tablets. It is worthwhile to consider paan consumption as a possible etiology of "refractory hypothyroidism" in individuals being treated with a standard LT4 replacement dose in India. Chronic paan chewing causes reddish discoloration of the tongue. Encountering such a finding on examination in a patient with persistently elevated thyroid-stimulating hormone (TSH) should prompt the treating physician to meticulously inquire about dietary patterns and other habits. This is important when there is a consistent denial of noncompliance and an absence of clinical suggestions of malabsorptive and systemic diseases. We describe here a patient with primary autoimmune hypothyroidism with persistently elevated TSH, despite being on an unusually high dose of LT4, due to his habit of paan chewing. The red- colored tongue provided us a clue about the habit. TSH normalization was achieved with the standard replacement dose of LT4 following the cessation of paan consumption.