Iodine Deficiency and Hypothyroidism From Voluntary Diet Restrictions in the US: Case Reports

The Increasing Prevalence of Autism Spectrum Disorder in the U.S. and Its Implications for Pediatric Micronutrient Status: A Narrative Review of Case Reports and Series

INTRODUCTION

Micronutrient deficiencies are considered uncommon in the United States. However, children with autism spectrum disorder (ASD) are at higher risk due to food selectivity and restrictive eating patterns. The prevalence of ASD in the U.S. has quadrupled over the past two decades, amplifying the need to address nutritional gaps in this population.

OBJECTIVE

This narrative review examines the prevalence and clinical impact of underreported micronutrient deficiencies beyond vitamin C in children with ASD using case reports and series.

METHODS

Case reports and case series reporting micronutrient deficiencies in children with ASD published from 2014 to 2025 were identified through PubMed and ScienceDirect using search terms "autism and deficiency" and "autism and vitamin A, K, magnesium, iron deficiency". Eligible cases included children aged 2-18 years with ASD and laboratory-confirmed micronutrient deficiencies.

RESULTS

A total of 44 cases from 27 articles were analyzed. Frequently reported deficiencies were vitamin D (25.0%), vitamin A (24.8%), B-vitamins (18.0%), calcium (10.8%), and iron (9.6%). Less common deficiencies included iodine, zinc, vitamin E, etc. Diseases such as xerophthalmia, rickets, pellagra, and goiter were reported. Co-occurring deficiencies were present in 70% of cases, and all cases reported food selectivity, with deficiencies occurring despite normal growth parameters in some children.

CONCLUSIONS

Based on cases reviewed, children with ASD are at high risk for micronutrient deficiencies, despite meeting normal growth parameters. Further research is needed to develop a standardized nutrition assessment, but combining anthropometric, biochemical, and dietary assessments can aid in early intervention and prevent complications.

Iodine Deficiency Hypothyroidism Among Children in the United States - 21st Century Resurgence?

Background/Objective

Iodine deficiency hypothyroidism is an important cause of neurocognitive and motor impairment in children globally. In the United States, universal salt iodization, which began in the 1920s, led to a dramatic decline in iodine deficiency hypothyroidism. However, iodine deficiency may be reemerging due to increased consumption of noniodized salts, decreased dairy iodine concentrations, and decreased intake of iodine containing foods due to food allergies, dietary preferences such as vegan diets, or restrictive food intake disorders.

Case Report

We present a case series that challenges the existing clinical paradigm for hypothyroidism and describe 3 patients without underlying thyroid dysfunction who were diagnosed with iodine deficiency hypothyroidism over an 18-month period beginning in February 2021 in Northeastern United States. Prior studies reported 2 additional cases diagnosed in that same time frame at our clinical center.

Discussion

We report significant heterogeneity in clinical presentation: 3 patients had large goiters, 1 had a mild goiter, and 1 patient had no goiter. Biochemical tests were also variable and included a wide range of thyroid stimulating hormone elevations.

Conclusion

We suggest that a spot urine iodine concentration, combined with an elevated serum thyroglobulin level, can be an alternative to a 24-hour urinary iodine excretion for the diagnosis of iodine deficiency hypothyroidism given the clinical challenges of obtaining the latter. Thyroid function normalized in all patients with iodine supplementation.

Thyroid function tests of iodine deficiency goiter can mimic thyroid hormone resistance alpha

OBJECTIVES

Iodine deficiency goiter can develop in children on a restrictive diet and most have normal thyroid function. We report a 6-year-old girl with iodine deficiency goiter with thyroid function studies mimicking thyroid hormone resistance alpha. Thyroid hormones mediate its effects through thyroid hormone receptors alpha and beta. Biochemical picture of low/low-normal T4 and high/high-normal T3 levels, variably reduced reverse T3 and normal TSH is characteristic of thyroid hormone resistance alpha.

CASE PRESENTATION

A 6-year-old girl, born out of non-consanguineous marriage presented with goiter of 1.5 years duration. She was without symptoms of thyroid dysfunction. The patient was evaluated at one year of age for macrocephaly with cranial ultrasound which was normal. She had normal growth and development. Patient was vegan and was not on any medications or supplements. Laboratory work up showed TSH 5.03 uIU/mL (0.34-5.5), FT4 0.3 ng/dL (0.58-1.2), FT3 5.3 pg/mL (2.5-3.9), total T3 258 ng/dL (94-241), reverse T3 <5.0 ng/dL (8.3-22.9) and negative thyroglobulin antibody and thyroid peroxidase antibody. Thyroglobulin level was 1,098.8 ng/mL (<13 ug/L), and urine iodine 15.8 ug/L (<100 ug/L) confirming a diagnosis of iodine deficiency goiter. Patient was started on iodine supplements, 150 ug daily and repeat work up 3 months later were TSH: 2.717 uIU/mL, T3, total 182 ng/dL, T4, total 9.3 ug/dL, FT 4 2.1 ng/dL.

CONCLUSIONS

Iodine deficiency goiter may present with low FT 4, elevated T3 and normal TSH mimicking thyroid hormone resistance alpha and should be considered in children on restrictive diet.

Association of Hypothyroidism and the Risk of Cognitive Dysfunction: A Meta-Analysis

Objectives: The purpose of this meta-analysis was to assess whether there is an association between hypothyroidism and the risk of cognitive dysfunction. Methods: PubMed, Cochrane Library, and Embase were searched for relevant studies published from database inception to 4 May 2022, using medical subject headings (MeSHs) and keywords. Results: Eight studies involving 1,092,025 individuals were included, published between 2010 and 2021. The pooled analysis showed that there was no association between hypothyroidism and cognitive dysfunction (OR = 1.13, 95% CI = 0.84−1.51, p = 0.426), including both all-cause dementia (OR = 1.04, 95% CI = 0.76−1.43, p = 0.809) and cognitive impairment (OR = 1.50, 95% CI = 0.68−3.35, p = 0.318). Neither overt hypothyroidism (OR = 1.19, 95% CI = 0.70−2.02, p = 0.525) nor subclinical hypothyroidism (OR = 1.04, 95% CI = 0.73−1.48, p = 0.833) was associated with cognitive dysfunction. Neither prospective cohort (OR = 1.08, 95% CI = 0.77−1.51, p = 0.673) nor cross-sectional studies (OR = 1.23, 95% CI = 0.63−2.42, p = 0.545) had any effect on the association. Interestingly, the risk of cognitive dysfunction was significantly increased in the group not adjusted for vascular comorbidity (OR = 1.47, 95% CI = 1.07−2.01, p = 0.017), while it was reduced in the adjusted group (OR =0.82, 95% CI = 0.79−0.85, p < 0.001). Conclusions: This meta-analysis shows that hypothyroidism was associated with a reduced risk of cognitive dysfunction after adjustment for vascular-disease comorbidities. More prospective observational studies are needed in the future to investigate the relationship between hypothyroidism and cognitive dysfunction.

Severe Hypothyroidism and Large Goiter due to Iodine Deficiency in an Adolescent Male in the United States: A Case Report and Review of the Literature

Acquired hypothyroidism due to iodine deficiency is extremely rare in the United States due to the introduction of table salt iodization in the 1920s (Leung et al., 2012). We present the case of an adolescent male with a history of mild autism spectrum disorder and an extremely restrictive diet who was found to have iodine deficiency as the etiology for his rapidly enlarging goiter and antibody-negative hypothyroidism. Thyroid-stimulating hormone (TSH) was 416 μIU/mL (0.350–5.500 μIU/mL), free thyroxine (T4) was <0.1 ng/dL (0.80–1.80 ng/dL), and triiodothyronine (T3) was 41 ng/dL (82–213 mg/dL) at diagnosis. The patient's 24-hour urinary iodine was undetectable. He was started on iodine supplementation with rapid visible improvement of goiter within two weeks and normalization of thyroid function tests within four weeks. Thorough dietary history and nutritional screening are important in cases of acquired hypothyroidism and/or goiter. Alternatively, diets that are low in iodized salt, dairy, bread, and seafood should raise concern for iodine deficiency, and patients with suspected or proven iodine deficiency should be screened for hypothyroidism.

Severe Acquired Primary Hypothyroidism in Children and its Influence on Growth: A Retrospective Analysis of 43 Cases

INTRODUCTION

Severe acquired hypothyroidism in childhood is a rare condition, mostly caused by autoimmune thyroiditis. Scarce and inconsistent data based on small patient numbers exist concerning its impact on growth in height.

METHODS

Patient files at a single centre university hospital over 8 years were retrospectively reviewed. We identified 43 patients (mean age 10.6 years, 3.3-15.25, 59% prepubertal, 88% females) in a cohort of children older than 3 years with an initial TSH>30 mIU/l and reduced T4 or fT4; congenital and drug-induced hypothyroidism were excluded.

RESULTS

All patients had signs of autoimmune thyroiditis (93% positive autoantibodies, 95% typical ultrasonography, 63% goiter). Median TSH was 100 mIU/l [0.3-4 mIU/l]), median fT4 3.55 pg/ml [8-19 pg/ml], median T4 2.85 µg/dl [5.3-11 µg/dl]. Presenting symptoms included goiter (26%), tiredness (23%), weight gain (19%), and growth retardation (19%). The diagnosis was made incidentally in 26% patients. In 75% growth was retarded (median height standard deviation score (SDS)-0.55), in 17% height SDS was<-2 at diagnosis. Midparental height SDS at diagnosis correlated significantly with T4 and fT4 (r=0.77, p=0.0012 and r=0.53, p=0.021 respectively). Catch-up growth under T4 substitution was significantly greater in prepubertal than in pubertal children (p 0.049).

CONCLUSION

This so far largest pediatric cohort with severe acquired hypothyroidism confirms a serious impact on growth which, however in most cases, showed a certain catch-up growth after adequate L-thyroxine therapy. The pubertal state seems to be important for catch-up growth. A significant number of patients were not diagnosed clinically, although affected by severe hypothyroidism.

Lifestyle is associated with thyroid function in subclinical hypothyroidism: a cross-sectional study

BACKGROUND

Few studies have focused on the association between lifestyle and subclinical hypothyroidism (SCH). The purpose of this study was to investigate the association between lifestyle and thyroid function in SCH.

METHODS

This study was a part of a community-based and cross-sectional study, the Epidemiological Survey of Thyroid Diseases in Fujian Province, China. A total of 159 participants with SCH (81 males and 78 females) and 159 euthyroid (87 males and 72 females) participants without any missing data were included in the analysis. General information and lifestyle information including sleep, exercise, diet and smoking habits of the participants was collected by questionnaire and Pittsburgh sleep quality index scale (PSQI) was collected. Thyroid stimulating hormone (TSH), free thyroxine (FT4), thyroid peroxidase antibody (TPOAb), thyroid globulin antibody (TgAb) and urine iodine concentration (UIC) were tested. Thyroid homeostasis parameter thyroid' s secretory capacity (SPINA-GT), Jostel's TSH index (TSHI), thyrotroph T4 sensitivity index (TTSI) were calculated. Logistic regression and multiple linear regression were performed to assess associations.

RESULTS

Compared with euthyroid subjects, patients with SCH were more likely to have poor overall sleep quality (15.1 vs.25.8 %, P = 0.018) and l less likely to stay up late on weekdays (54.7 vs. 23.9 % P < 0.001). In SCH group, exercise was the influencing factor of TSH (β= -0.224, P = 0.004), thyroid secretory capacity (β = 0.244, P = 0.006) and thyrotropin resistance (β = 0.206, P = 0.009). Iodine excess was the influencing factor of thyroid secretory capacity (β = 0.209, P = 0.001) and pituitary thyroid stimulating function (β = 0.167, P = 0.034). Smoking was the influencing factor of pituitary thyroid stimulating function (β = 0.161, P = 0.040). Staying up late on weekends was the influencing factor of thyroid secretory capacity (β = 0.151, P = 0.047). After adjusting for possible confounders, logistic regression showed that those with poor overall sleep quality assessed by PSQI and iodine excess had an increased risk of SCH (OR 2.159, 95 %CI 1.186-3.928, P = 0.012 and OR 2.119, 95 %CI 1.008-4.456, P = 0.048, respectively).

CONCLUSIONS

Lifestyle including sleep, smoking, diet and exercise was closely related to thyroid function especially thyroid homeostasis in SCH.

Mild-to-Moderate Gestational Iodine Deficiency Processing Disorder

This synopsis paper aims to identify if a common pattern of learning and social difficulties can be conceptualized across recent longitudinal studies investigating the influence of mild-to-moderate gestational iodine deficiency (GID) on offspring's optimal cognitive and psycho-social development. The main studies investigated are: The Southampton Women's Study (SWS)-United Kingdom; the Avon Longitudinal Study of Parents and Children (ALSPAC)-United Kingdom; the Gestational Iodine Cohort Longitudinal Study-Tasmania, Australia, and the Danish National Birth Cohort Case-Control Study-Denmark. In contrast to severe GID where there is a global negative impact on neurodevelopment, mild-to-moderate intrauterine iodine deficiency has subtler, but nonetheless important, permanent cognitive and psycho-social consequences on the offspring. This paper links the results from each study and maintains that mild-to-moderate GID is associated with a disorder that is characterized by speed of neural transmitting difficulties that are typically associated with working memory capacity difficulties and attention and response inhibition. The authors maintain that this disorder is better identified as Gestational Iodine Deficiency Processing Disorder (GIDPD), rather than, what to date has often been identified as 'suboptimal development'. The Autistic Spectrum Disorder (ASD), Attention Deficit, Hyperactivity Disorder (ADHD), language and literacy disorders (learning disabilities and dyslexia) are the main manifestations associated with GIDPD. GIDPD is identified on IQ measures, but selectively and mainly on verbal reasoning IQ subtests, with individuals with GIDPD still operating within the 'normal' full-scale IQ range. Greater consideration needs to be given by public health professionals, policy makers and educators about the important and preventable consequences of GID. Specifically, more emphasis should be placed on adequate iodine intake in women prior to pregnancy, as well as during pregnancy and when lactating. Secondly, researchers and others need to further extend, refine and clarify whether GIDPD, as a nosological (medical classification) entity, is a valid disorder and concept for consideration.

Evaluation and management of the child with hypothyroidism

BACKGROUND

Thyroid hormones are critical for early neurocognitive development as well as growth and development throughout childhood. Prompt recognition and treatment of hypothyroidism is, therefore, of utmost importance to optimize physical and neurodevelopmental outcomes.

DATA SOURCES

A PubMed search was completed in Clinical Queries using the key terms "hypothyroidism".

RESULTS

Hypothyroidism may be present at birth (congenital hypothyroidism) or develop later in life (acquired hypothyroidism). Thyroid dysgenesis and dyshormonogenesis account for approximately 85% and 15% of permanent cases of congenital primary hypothyroidism, respectively. More than 95% of infants with congenital hypothyroidism have few, if any, clinical manifestations of hypothyroidism. Newborn screening programs allow early detection of congenital hypothyroidism. In developed countries, Hashimoto thyroiditis is the most common cause of goiter and acquired hypothyroidism in children and adolescents. Globally, iodine deficiency associated with goiter is the most common cause of hypothyroidism. Central hypothyroidism is uncommon and may be associated with other congenital syndromes and deficiencies of other pituitary hormones. Familiarity of the clinical features would allow prompt diagnosis and institution of treatment.

CONCLUSIONS

To optimize neurocognitive outcome in infants with congenital hypothyroidism, treatment with levothyroxine should be started as soon as possible, preferably within the first 2 weeks of life. Children with acquired hypothyroidism should also be treated early to ensure normal growth and development as well as cognitive outcome. The target is to keep serum TSH < 5 mIU/L and to maintain serum free T4 or total T4 within the upper half of the age-specific reference range, with elimination of all symptoms and signs of hypothyroidism.

Development of Databases on Iodine in Foods and Dietary Supplements

Iodine is an essential micronutrient required for normal growth and neurodevelopment; thus, an adequate intake of iodine is particularly important for pregnant and lactating women, and throughout childhood. Low levels of iodine in the soil and groundwater are common in many parts of the world, often leading to diets that are low in iodine. Widespread salt iodization has eradicated severe iodine deficiency, but mild-to-moderate deficiency is still prevalent even in many developed countries. To understand patterns of iodine intake and to develop strategies for improving intake, it is important to characterize all sources of dietary iodine, and national databases on the iodine content of major dietary contributors (including foods, beverages, water, salts, and supplements) provide a key information resource. This paper discusses the importance of well-constructed databases on the iodine content of foods, beverages, and dietary supplements; the availability of iodine databases worldwide; and factors related to variability in iodine content that should be considered when developing such databases. We also describe current efforts in iodine database development in the United States, the use of iodine composition data to develop food fortification policies in New Zealand, and how iodine content databases might be used when considering the iodine intake and status of individuals and populations.