Elsevier

Clinical Nutrition

Volume 28, Issue 3, June 2009, Pages 256-259
Clinical Nutrition

Original Article
Requesting iodine supplementation in children on parenteral nutrition

https://doi.org/10.1016/j.clnu.2009.02.005Get rights and content

Summary

Background & aims

Iodine supplementation of parenterally fed infants recommended by ESPGHAN is 1 μg/kg/day. To assess nutritional and thyroid status of children on parenteral nutrition (PN) through urinary iodine concentration (UIC).

Patients and methods

Children (1–17 yrs), undergoing PN and receiving an iodine supply of 1 μg/kg/day, were enrolled from 2000 to 2007.

Results

We observed 15 children (10 males, mean age 76.53 ± 60.4 months) on PN from 14 to 84 weeks (mean 38.5 ± 21.4). Ten were on TPN and five on PPN; nine had short bowel syndrome (SBS) and six had other intestinal diseases requiring PN. Iodine supply in TPN ranged between 1 and 1.6 μg/kg/day (mean 1.1 ± 0.3 μg/kg/day), while in PPN it ranged from 2.3 to 2.8 μg/kg/day (mean 2.6 ± 0.7 μg/kg/day).

We found an inverse correlation between duration of PN in months and UIC (P = 0.05). Four weeks after PN onset, UIC < 100 μg/L was found in all SBS patients and 3/6 non-SBS patients (P < 0.05). After 12 weeks, 8/15 (53%) patients had UIC < 50 μg/L, but thyroxine, TSH and thyroid volume remained unchanged.

Conclusions

A PN iodine supply of 1 μg/kg/day may be suboptimal. Higher supplies should be evaluated in controlled trials.

Introduction

Iodine is a trace element essential for the synthesis of thyroid hormones1 that are responsible for the normal development of the brain, proliferation of neurons, and regulation of processes that involve cerebral functions.2 Daily iodine requirements in humans vary from 90 μg in neonates to 225–350 μg in women during pregnancy and lactation.3, 4, 5 The median UI that indicates an optimal iodine nutrition during these three periods should be in the range of 150–230 μg/day.3, 4, 5

Iodine deficiency is the first cause of avoidable mental deficiency in developed countries. It has not yet disappeared in Europe, and in Eastern Europe it is responsible for a high prevalence of goitre.6, 7, 8 Two billion individuals worldwide have insufficient iodine intake, with those in south Asia and sub-Saharan Africa particularly affected.8

Patients who use nutritional support for long periods risk multiple nutrient deficiencies. Deficiencies in iron, zinc, vitamin, and magnesium have been found in patients with malabsorption after long periods of total parenteral nutrition.9, 10 Despite numerous indications of iodine deficiency disorders in conditions of chronic malnutrition and in countries with a moderate iodine deficiency,6, 7 little is known about iodine status and its consequences in children on parenteral nutrition (PN). Patients' micronutrient needs, that are not always met by PN solutions, or lower absorption may explain these findings. Consequently, micromineral deficiencies might be a serious problem in the clinical follow-up of these patients.9, 10

There is a strong correlation between iodine urinary excretion and intake, so urinary iodine concentration (UIC, μg/L) can be useful as a parameter of iodine status in healthy orally fed individuals with normal fluid intake.11, 12, 13 Iodine measuring in one sample of urine (UIC) is currently used as the standard biochemistry method for the evaluation of iodine deficiency.2, 5, 11, 14 A light iodine deficiency is considered when iodine concentration is lower than 100 μg/L, a moderate deficiency when iodine concentration is lower than 50 μg/L, and a severe deficiency when iodine concentration is lower than 20 μg/L. Individuals with total urinary iodine excretion levels above 100 μg/L are considered normal.3, 6, 12

Associations have been found between thyroid hormones, total iodine intake and iodine urinary excretion: normal levels of TSH and free T4 generally indicate an adequate availability of iodine,13 but some studies have suggested that even normal levels of TSH and T4 do not exclude the possibility of inadequate iodine intake.15, 16, 17 The subjects are at risk of enlarged thyroids, which may not regress completely even after adjustment of iodemia.

The iodine supplementation of parenterally fed infants of The American Society for Clinical Nutrition recommendations is of 1 μg/kg/day.18 Following these recommendations, in a PN study in 1992 Moukarzel et al. showed normal thyroid hormone and iodide levels in children and concluded that these iodide recommendations were adequate19; however, this was against a background of a high usage of povidone iodine as a skin disinfectant, and the use of iodinated contrast media to visualise the position of long-lines. The evidence for the efficacy of chlorhexidine as a far better skin disinfectant compared to povidone iodine has reduced its use, and radiologically more sensitive catheters have reduced the need for iodinated contrast visualisation. On the other hand, the ESPGHAN guidelines 2005, after suggesting a daily iodine supply of 1 μg/kg/day, acknowledge that changes in practice have occurred and recommend a “need for reassessment of iodine requirements”.20

The aim of this study is to evaluate the iodine status (intake and urinary excretion) in children with intestinal malabsorption and on total parenteral nutrition (TPN, 100% of kcal from parenteral nutrition) and partial parenteral nutrition (PPN, 50% or less from parenteral nutrition). These patients receive an iodine supply of 1 μg/kg/day according to ESPGHAN Guidelines on Paediatric Parenteral Nutrition 2005.20 Our aim was also to validate the UIC as a monitoring test of iodine intake during PN.

Section snippets

Patients and methods

We studied prospectically 15 children undergoing PN for periods from 14 to 84 weeks (mean 38.5 ± 21.4 weeks), 10 boys and 5 girls, aged from 1 to 17 years, mean age 76.53 ± 60.4 months, observed at the Department of Pediatrics, University of Naples Federico II, between 2000 and 2007. Ten patients were on TPN and five were on PPN. Nine had short bowel syndrome (SBS) and six had other intestinal diseases requiring parenteral support (Table 1). Exclusion criteria were thyroid-related diseases

Results

Our 15 patients on PN received 1 μg/kg/day of iodine supply. The supplementation of iodine in the TPN group ranged between 1 and 1.6 μg/kg/day, mean 1.1 ± 0.3 μg/kg/day, while the estimated daily iodine intakes in PPN group, considering also the food plus salt consumed and/or enteral nutrition, ranged from 2.3 to 2.8 μg/kg/day, mean 2.6 ± 0.7 μg/kg/day. There was not a statistically significant difference between the two groups.

The total fluid intake (parenteral and enteral nutrition) varied depending

Discussion

Urinary iodine concentration (UIC, μg/L), measured on single urine samples in the nonfasted state, is the most reliable index of iodine availability in healthy orally fed individuals with normal fluid intake because it reflects iodine intake from foodstuff shortly before sampling (it peaks following the three main meals by 4–5 h) and the intraindividual UIC variability in nonfasting subjects is rather limited in comparison with the interindividual one.23 Because most iodine is excreted on the

Conflict of interest

None declared.

Acknowledgments

We would like to thank Dr Jean Gilder, a professional author's editor and member of the European Association of Science Editors (EASE) and of the Council of Science Editors, who has revised and edited the paper.

References (23)

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    Iodine requirements during pregnancy, lactation and the neonatal period and indicators of optimal iodine nutrition

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    A professional author's editor, who is a longstanding member of the European Association of Science Editors (EASE) and of the Council of Science Editors, and whose first language is English, has revised and edited the paper.

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