Patients with ID (with or without anemia) commonly complain of cold sensitivity. Like other symptoms of ID, the patient rarely volunteers this history must be directly questioned about the symptom. Studies in animals and humans have shown that iron deficiency impairs thyroid metabolism (which is involved in heat production) and thermogenesis of brown adipose tissue. Mechanisms underlying the effect of iron on thyroid metabolism thermogenesis of brown adipose tissue are not clear, but may include:
- Thyroid peroxidase, which is involved in generating T3, T4, is a heme-containing protein.
- Heme is essential component of cytochrome c in electron transport chain, and is used for formation of Fe-S clusters in brown adipocytes.
Cold sensitivity quickly resolves with iron supplementation.