Low iodine diet in differentiated thyroid cancer: a review

Abstract

SummaryRadioactive iodine (RAI) ablation is a beneficial, adjuvant therapy for the management of differentiated thyroid cancer (DTC) after thyroidectomy. The goal of RAI is to destroy remnant thyroid and microscopic cancerous tissue. Radioactive iodine uptake is enhanced by elevating TSH levels and initiating a low iodine diet (LID) prior to ablation. An ideal LID should preferably not exceed 50 mcg/day of dietary iodine for 1-2 weeks, although the duration may be shortened to a week with a structured patient education programme. A pre-ablation spot urinary iodine concentration (UIC) of <100 mcg/l and/or a urinary iodine to creatinine ratio (UICR) of <100 mcg/gCr would support an adequate LID preparation. Hyponatraemia, most likely due to iatrogenic hypothyroidism, is a potential side effect associated with LID and occurs during and a few days after the LID. Although the overall incidence of hyponatraemia is low, patients at high risk (older age, female sex, use of thiazide diuretics) may benefit from serum sodium monitoring. The existing evidence on the impact of LID on RAI ablation has been largely inconsistent due to retrospective study designs and the lack of an objective measurement of urinary iodine levels. Future large prospective randomized control trials are needed to elucidate and confirm the crucial role of LID in achieving successful RAI ablation and greater disease-free survival in DTC.

Thyroid cancer mortality is higher in Filipinos in the United States: An analysis using national mortality records from 2003 through 2012

“…Studies examining diet and thyroid cancer outcome are scarce. Post-thyroidectomy thyroid cancer patients are often placed on low-iodine diets before radioactive iodine (RAI) treatment in order to enhance I-131 uptake and maximize the destruction of cancerous thyroid cells 13 . One study found that among a cohort of Korean females, approximately 37% did not know that fish pastes, hams, and sausages contained high levels of iodine, and 36% over-estimated the amount of dairy they were allowed to consume on a low-iodine diet 14 .…”

Effects of Thyroid Hormone on Urinary Concentrating Ability

“…A second limitation is the low-iodine diet which patients had to adhere to in order to increase the effectiveness of RAI treatment. Although this diet is different from a “low-sodium” diet, any foods containing iodized salt and sea salt were not allowed [19]. Therefore, we cannot exclude that this diet might have influenced the sodium and chloride levels and hence osmolality in our patients during hypothyroidism.…”

Pattern of urine iodine excretion with low iodine diet during preparation for radioactive iodine ablation in patients with thyroid cancer

“…The purpose of iodine restriction is to increase the expression of the sodium‐iodide symporter (NIS) in the thyroid follicular cells by lowering the iodine concentration within the body. It also minimizes the competitive handling of nonradioactive iodine instead of the radioactive iodine by the NIS …”