Re: uptake of I131 by salivary glands

 www.medscape.com/viewarticle/456955_2

The salivary glands also have the capacity to concentrate iodide selectively for unknown reasons (Fig. 1). The iodide is then secreted into saliva such that its salivary concentration has been reported to vary from 20 to 100 times that found in the serum.^[5-10] It is this critical ability that causes glandular damage when ¹³¹I is used. The principal site of the iodide transport into saliva is the epithelium of the parotid salivary gland's intralobular ducts.^[11,12] Iodide is extracted from periductal capillaries and concentrated by the ductal epithelium, whereupon it is secreted into the duct lumen and transported into the oral cavity. It has been calculated that up to 24% of the administered ¹³¹I dose for thyroid cancer therapy is lost in the saliva.^[13]

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Lateral head and neck planar view acquired with a low energy collimator 24 hours after oral administration of 2.0 mCi 123I in a patient with papillary thyroid cancer undergoing diagnostic scanning prior to 131I therapy for thyroid remnant ablation. Normal physiologic uptake of radioiodine by the salivary glands is indicated.