Sinonasal Symptom Outcomes following Endoscopic Anterior Cranial Base Surgery in the Pediatric Population.

Objective This study aimed to evaluate the impact of endoscopic anterior cranial base (ACB) surgery on sinonasal symptoms in the pediatric population utilizing the Sino-Nasal Outcome Test (SNOT)-22 questionnaire. Design This is a retrospective review. Setting The study was conducted at a tertiary academic medical center. Participants Thirty-four consecutive patients, age 6 to 17 years, M:F 14:20, who underwent endoscopic ACB surgery from July 2008 to August 2019. Ten patients had baseline and a minimum of two subsequent postoperative SNOT-22 questionnaires available for analysis. Main Outcome Measures Baseline and postoperative SNOT-22 scores were compared. The mean change from baseline sinonasal symptom scores in the pediatric and historical adult cohorts was compared. Results The mean baseline SNOT-22 score for our 10 patient cohort was 0.46 out of 5 for each of the first 10 sinonasal-specific questions. This worsened to 1.69 at 1 month and returned to near baseline, 0.7, at 3 months postoperatively. The mean quality-of-life score improved to 0.91 at 1 month and 0.6 at 3 months postoperatively. The mean change from baseline for the following items: need to blow nose, runny nose, postnasal discharge, thick nasal discharge, wake up at night, reduced concentration, and frustrated/restless/irritable were similar to those in our historical adult cohort at 3 months postoperatively. Conclusion Endoscopic ACB surgery in the pediatric population results in increased sinonasal symptom morbidity in the early postoperative period; however, symptoms return to near baseline by ∼3 months, and quality-of-life scores progressively improve in the postoperative period. These trends were similar to those seen in our historic adult cohort.

Prepubescent unilateral gynecomastia secondary to excessive soy consumption.

OBJECTIVE: We present a case of an unusual cause of prepubertal gynecomastia. CASE PRESENTATION: Enlargement of breast tissue in males, or gynecomastia, is a rare condition in prepubescent boys. We describe an 8-year-old male who developed unilateral gynecomastia secondary to marked dietary soy consumption. While the majority of cases are idiopathic, soy products, particularly those consumed by our patient, can contain high levels of phytoestrogens, which have been documented in limited case studies to contribute to abnormal development of breast tissue in adolescent and adult males. To our knowledge, this is the first documented case of gynecomastia occurring in a prepubescent patient resulting from excessive intake of dietary soy. Importantly, we also report a complete resolution of gynecomastia upon exclusion of dietary products containing significant amounts of soy. CONCLUSION: While soybeans and soy-derived products can be an important source of nutrition for some, those with abnormal sensitivity to phytoestrogens may benefit from limiting dietary soy consumption to avoid potential adverse effects, including gynecomastia.

Recombinant human thyroid-stimulating hormone versus thyroid hormone withdrawal preparation for radioiodine ablation in differentiated thyroid cancer in children, adolescents and young adults.

OBJECTIVE: Recombinant human TSH (rhTSH) is commonly used to prepare patients for postoperative radioiodine (I-131) ablation after surgery for differentiated thyroid cancer (DTC). In adults, rhTSH is associated with equivalent oncologic efficacy in comparison to thyroid hormone withdrawal (THW), but its use has not been well studied in children. We aimed to measure time to disease progression after rhTSH stimulation vs. THW in paediatric patients under the age of 21 with DTC following total thyroidectomy. DESIGN: Retrospective cohort study (March 2001-July 2018). PATIENTS: Sixteen children and adolescents (75% female, median age, 17.4 years) who received rhTSH were compared to 29 historical controls (72% female, median age, 18.5 years) prepared with THW, followed for a median of 2.4 years (range, 0.5-14). MEASUREMENTS: Stimulated serum TSH concentrations prior to I-131 ablation and time to disease progression, as determined by a component outcome variable encompassing both structural and biochemical disease persistence/recurrence. RESULTS: No differences were observed in tumour characteristics and I-131 dose (median 2.3 [1.8-2.90] mCi/kg rhTSH) between groups. Patients who received rhTSH achieved a similar median stimulated TSH level (163 [127-184] mU/L), compared to those who underwent THW (136 [94.5-197] mU/L; p = .20). Both groups exhibited similar time to progression (p = .13) and disease persistence/recurrence rates (rhTSH 31% vs. THW 59%, p = .14). CONCLUSION: In this cohort of children and adolescents with DTC, we observed similar time to disease progression among those who received rhTSH or underwent THW prior to postoperative I-131 ablation.

Hyperandrogenism and malignant degeneration of hepatic adenomas in the setting of Abernethy malformation.

Abernethy malformation refer to a congenital absence of intrahepatic portal veins leading to a primarily extrahepatic congenital portosystemic shunt. The lack of intrahepatic portal veins leads to a characteristic set of physical exam and imaging findings that may include hyperandrogenism and liver masses such as hepatic adenomas or focal nodular hyperplasia. In this case report, we describe a 20-year-old female who presented with an enlarging hepatic adenoma. A separate hepatic adenoma had previously been biopsied and noted to have undergone malignant degeneration into hepatocellular carcinoma. For each lesion, she was treated with combination transarterial embolization and microwave ablation. On follow-up imaging after therapy, it was then noted that her extrahepatic portal vein drained directly into the inferior vena cava, consistent with congenital portosystemic shunt. Recognition of this vascular anomaly is critical in treatment planning, as early intervention with either medical therapy or surgery can prevent the metabolic sequela of this unique constellation of symptoms.

Iodine Nutrition in Weaning Infants in the United States.

BACKGROUND: As iodine is a requisite micronutrient for infant brain development, infants are at risk for iodine deficiency during the weaning period when their diet transitions from milk (breast-milk, infant formula, or follow-on formula) to solid food. Dietary iodine intake during this weaning period is likely minimal, as the iodine content of commercial baby food is not regulated, and the addition of salt to baby food is not recommended. This study reports the current status of iodine nutrition among weaning infants in the United States. METHODS: Subjects (n = 60; 50% Caucasian, 30% black) were infants <12 months of age who were fed any combination of formula and/or baby food. Samples of all formula and food consumed in the previous 24 hours and a spot urine sample from each infant were obtained for the measurement of iodine. The estimated quantities of ingested formula and baby food were summed from a food diary recorded by the infants' parents. RESULTS: The mean age of the infants was 6.3 ± 3.5 months. The median urinary iodine concentration (UIC) was 117 µg/L (range 26.9-1302.8 µg/L). Estimated daily iodine intake obtained from the measured iodine content in infant formula/foods was 89 µg (range 0-288 µg). There was a positive correlation between the infants' UIC and the iodine content in the consumed foods (r = 0.4, p < 0.001). CONCLUSIONS: Although the median UIC of infants fed a combination of infant formula and baby food would meet the criteria for iodine sufficiency in a larger sample, those consuming the lowest quartile of iodine-containing nutritional sources had a median UIC <100 µg/L.

PRE-ABLATION THYROGLOBULIN AND THYROGLOBULIN TO THYROID-STIMULATING HORMONE RATIO MAY BE ASSOCIATED WITH PULMONARY METASTASES IN CHILDREN WITH DIFFERENTIATED THYROID CANCER.

OBJECTIVE: Pediatric differentiated thyroid cancer (DTC) frequently presents with extensive disease. We studied the value of pre-ablation thyroglobulin (Tg) and Tg normalized to thyroid-stimulating hormone (TSH) levels in predicting distant metastases in pediatric patients with DTC. METHODS: This is a retrospective cohort study of patients <21 years old who underwent thyroidectomy followed by 131I ablation for DTC at 3 university hospitals over 20 years. Tg levels and the Tg/TSH ratio following surgery but prior to 131I ablation were assessed. The presence of distant metastatic disease was determined from the postablation whole-body scan. RESULTS: We studied 44 patients with a mean age of 15.2 years (range 7 to 21 years) and mean tumor size of 2.8 cm. Eight patients had distant metastases and had a higher mean pre-ablation Tg value compared to patients without distant metastases (1,037 µg/L versus 93.5 µg/L, P<.01). The pre-ablation Tg/TSH ratio was also associated with the presence of distant metastases: 12.5 ± 18.8 µg/mU in patients with distant metastases versus 0.7 ± 1.8 µg/mU in patients without (P<.01). A nomogram to predict distant metastases yielded areas under the receiver operating characteristic curve of 0.85 for Tg and 0.83 for Tg/TSH ratio. CONCLUSION: After initial thyroidectomy, elevated preablation Tg and Tg/TSH ratio are associated with distant metastatic disease in pediatric DTC. This may inform the decision to ablate with 131I, as well as the dosage. ABBREVIATIONS: ATA = American Thyroid Association CI = confidence interval DTC = differentiated thyroid cancer OR = odds ratio ROC = receiver operating characteristic Tg = thyroglobulin.

Thyroid Dysfunction in Children Exposed to Iodinated Contrast Media.

CONTEXT: Iodinated contrast media (ICM) is routinely used in imaging studies and contains several 100-fold the recommended daily allowance of iodine. OBJECTIVE: To determine whether children exposed to ICM have a higher risk of iodine-induced thyroid dysfunction. DESIGN: This was a single-institution case-control study, examining patients with incident thyroid dysfunction aged less than 18 years from 2001 to 2015. Cases were matched 1:1 to euthyroid controls by age, sex, and race. SETTING: This was a single-institution case-control study occurring at tertiary care center. PARTICIPANTS: Cases were defined as those with thyroid dysfunction (by International Classification of Diseases, Ninth Revision diagnosis codes and/or 2 consecutive abnormal serum TSH values <6 mo apart). We analyzed 870 cases matched to 870 controls (64% female, 51% White). MAIN OUTCOMES MEASURES: Using conditional logistic regression, the association between ICM exposure and the primary outcome, thyroid dysfunction, occurring within 2 years of exposure was assessed. RESULTS: Sixty-nine patients received ICM, including 53 (6%) among cases and 16 (2%) among controls. The risk of incident hypothyroidism was significantly higher after ICM exposure (odds ratio 2.60; 95% confidence interval, 1.43-4.72; P < .01). The median interval between exposure and onset of hypothyroidism was 10.8 months (interquartile range, 6.6-17.9). In hypothyroid cases, the median serum TSH concentration was 6.5 mIU/L (interquartile range, 5.8-9.6). CONCLUSIONS: ICM exposure increases the risk of incident hypothyroidism in pediatric patients. Children receiving ICM should be monitored for iodine-induced thyroid dysfunction, particularly during the first year after exposure.

Necrotizing Enterocolitis in the Full-Term Infant.

Necrotizing enterocolitis in full-term infants is relatively rare. When seen, it is usually associated with perinatal asphyxia, sepsis, or specific forms of congenital heart disease. It can also be associated with endocrinopathies. In this review, a full-term infant was found to have necrotizing enterocolitis and persistent hypoglycemia. Evaluation for hypoglycemia revealed pan-hypopituitarism, and magnetic resonance imaging confirmed this diagnosis. Timely evaluation and early initiation of hormone replacement therapy is essential to minimize long-term morbidities and mortality associated with pan-hypopituitarism.

Reproductive outcomes and nononcologic complications after radioactive iodine ablation for well-differentiated thyroid cancer.

BACKGROUND: Radioactive iodine (RAI) ablation is frequently performed after initial surgery for well-differentiated thyroid cancer (WDTC). We examined the frequency and timing of childbirth as well as nononcologic complications after RAI ablation for WDTC on a population level. METHODS: A retrospective cohort study of 25,333 patients (18,850 women) with WDTC was performed using the California Cancer Registry and California Office of Statewide Health Planning and Development database, 1999-2008. The primary outcomes were birthrate and median time to first live birth among women of childbearing age. Secondary outcomes were nononcologic diagnoses occurring outside the acute setting (>30 days) after ablation. RESULTS: RAI ablation did not affect birthrate among women in the full dataset. However, in subgroup analyses, birthrate among women age 35-39 was significantly decreased in those who received RAI versus those who did not (11.5 versus 16.3 births per 1000 woman-years, p<0.001). Median time to first live birth after diagnosis of WDTC was prolonged among women who received RAI compared to those who did not (34.5 versus 26.1 months; p<0.0001). When 5-year age groups were examined individually, delay to first live birth was observed in women age 20-39 (p<0.05). This remained significant after adjustment for tumor characteristics, socioeconomic status, and marital status. The only nononcologic, nonreproductive adverse effect associated with RAI ablation was an increased rate of nasolacrimal stenosis (RR 3.44, p<0.0001). CONCLUSIONS: RAI ablation is associated with delayed childbearing in women across most of the reproductive lifespan, and with decreased birthrate in the late reproductive years. The underlying mechanism likely involves physician recommendation to delay pregnancy, as well as a potential impact of RAI on both reproductive choice and reproductive health. Further investigation is merited.

Reversible left recurrent laryngeal nerve palsy in pediatric Graves' disease.

Vocal cord paralysis associated with goiter usually indicates the presence of a malignancy. Pediatric patients retain significant thymic tissue that regresses only later in life. This thymic tissue can develop significant hyperplasia during an acute autoimmune process. We describe a case of a 17-year-old girl who presented with a goiter secondary to severe Graves' disease and a 2-month history of hoarseness, choking on liquid intake, and small-volume vomiting especially after eating. She demonstrated a left vocal cord paralysis probably secondary to a unilateral left recurrent laryngeal nerve palsy. A marked enlargement of the thymus was discovered on thoracic imaging. Treatment was initiated with methimazole, with near complete remission of her vocal cord paralysis within 3 months. Given the immunomodulatory effects of methimazole, a potential mechanism of the left recurrent laryngeal nerve palsy was autoimmune hyperstimulation of the thymus and consequent hyperplasia, resulting in distension of the nerve. Attenuation of the hyperactive immune process with methimazole may have resulted in regression of the mass effect of the thymus and associated reduction of the nerve distension. This case illustrates the unique risk of left recurrent laryngeal nerve palsy in pediatric patients with an acute immune stimulation and hyperplasia of the thymus and the reversibility in the context of mitigation of the immune hyperactivity. Methimazole may be an optimal initial treatment choice in pediatric patients with Graves' disease and left recurrent laryngeal nerve palsy.

Correlation of TSH with the risk of paediatric thyroid carcinoma.

OBJECTIVE: Risk factors for the rare and unique entity of paediatric thyroid cancer are becoming more clearly defined. This study investigated the association of thyroid-stimulating hormone (TSH) with the diagnosis of differentiated thyroid carcinoma in the paediatric population. No previous studies have correlated the paediatric thyroid cancer risk with TSH levels. DESIGN: Retrospective case-controlled study. PATIENTS: A total of 116 paediatric patients with an indication for thyroidectomy referred to Seattle Children's Hospital, a major paediatric tertiary medical centre, between January 1997 and January 2011 were assessed. Excluding confounders that would directly affect TSH values, 78 patients (29 patients with and 49 patients without thyroid cancer) between the ages of 3 and 20 years were evaluated. MEASUREMENTS: Preoperative TSH values correlated with pathology review of en bloc resected thyroid tissue specimens. RESULTS: The diagnosis of paediatric thyroid carcinoma was significantly associated with elevated TSH levels. The average TSH level (2·32 ± 0·51 mIU/l) was significantly greater than the TSH level (1·08 ± 0·14 mIU/l) noted in patients without malignancy (P = 0·03). A rightward skew of TSH was associated with paediatric patients harbouring paediatric thyroid carcinoma, with a TSH level ≥2·50 mIU/l correlating with a significantly increased odds ratio of thyroid cancer (OR 8·05, 95% CI 1·41-81·39, P = 0·0073) relative to a normal TSH range of 0·40-2·49 mIU/l. CONCLUSIONS: Paediatric thyroid carcinoma is associated with TSH level ≥ 2·50 mIU/l, which may be useful to identify a higher risk of malignancy in a paediatric patient with a thyroid nodule.

Parenteral insulin suppresses T cell proliferation to islet antigens.

The diabetes prevention trial-type 1 (DPT-1) tested whether a combination of SQ and IV insulin therapy would delay the onset of disease in individuals at high risk of progression. We investigated whether this regimen altered T cell responses to human islet proteins using cellular immunoblotting. Among the 10 treated and 7 control subjects studied, we found that there was a significant effect of treatment on cellular immunoblotting responses. We conclude that parenteral insulin may suppress proliferation to islet antigens in individuals at risk for diabetes, but this effect may be transient. Further study is needed to determine whether a therapy that results in sustained suppression of T cell proliferation could yield a measurable clinical benefit.

Impact of heterozygosity for acid-labile subunit (IGFALS) gene mutations on stature: results from the international acid-labile subunit consortium.

CONTEXT: To date, 16 IGFALS mutations in 21 patients with acid-labile subunit (ALS) deficiency have been reported. The impact of heterozygosity for IGFALS mutations on growth is unknown. OBJECTIVE: The study evaluates the impact of heterozygous expression of IGFALS mutations on phenotype based on data collected by the International ALS Consortium. SUBJECTS/METHODS: Patient information was derived from the IGFALS Registry, which includes patients with IGFALS mutations and family members who were either heterozygous carriers or homozygous wild-type. Within each family, the effect of IGFALS mutations on stature was analyzed as follows: 1) effect of two mutant alleles (2ALS) vs. wild-type (WT); 2) effect of two mutant alleles vs. one mutant allele (1ALS); and 3) effect of one mutant allele vs. wild-type. The differences in height sd score (HtSDS) were then pooled and evaluated. RESULTS: Mean HtSDS in 2ALS was -2.31 +/- 0.87 (less than -2 SDS in 62%); in 1ALS, -0.83 +/- 1.34 (less than -2 SDS in 26%); and in WT, -1.02 +/- 1.04 (less than -2 SDS in 12.5%). When analyses were performed within individual families and pooled, the difference in mean HtSDS between 2ALS and WT was -1.93 +/- 0.79; between 1ALS and WT, -0.90 +/- 1.53; and between 2ALS and 1ALS, -1.48 +/- 0.83. CONCLUSIONS: Heterozygosity for IGFALS mutations results in approximately 1.0 SD height loss in comparison with wild type, whereas homozygosity or compound heterozygosity gives a further loss of 1.0 to 1.5 SD, suggestive of a gene-dose effect. Further studies involving a larger cohort are needed to evaluate the impact of heterozygous IGFALS mutations not only on auxology, but also on other aspects of the GH/IGF system.

Mice lacking hepatic lipase are lean and protected against diet-induced obesity and hepatic steatosis.

Hepatic lipase (HL)-mediated lipoprotein hydrolysis provides free fatty acids for energy, storage, and nutrient signaling and may play a role in energy homeostasis. Because HL-activity increases with increased visceral fat, we hypothesized that increased HL-activity favors weight gain and obesity and consequently, that HL deficiency would reduce body fat stores and protect against diet-induced obesity. To test this hypothesis, we compared wild-type mice (with endogenous HL) and mice genetically deficient in HL with respect to daily body weight and food intake, body composition, and adipocyte size on both chow and high-fat (HF) diets. Key determinants of energy expenditure, including rate of oxygen consumption, heat production, and locomotor activity, were measured by indirect calorimetry. HL-deficient mice exhibited reduced weight gain on both diets (by 32%, chow; by 50%, HF; both P < 0.0001, n = 6-7 per genotype), effects that were associated with reduced average daily food intake (by 22-30% on both diets, P < 0.0001) and a modest increase in the rate of oxygen consumption (by 25%, P < 0.003) during the light cycle. Moreover, in mice fed the HF diet, HL deficiency reduced both body fat (by 30%, P < 0.0001) and adipocyte size (by 53%, P < 0.01) and fully prevented the development of hepatic steatosis. Also, HL deficiency reduced adipose tissue macrophage content, consistent with reduced inflammation and a lean phenotype. Our results demonstrate that in mice, HL deficiency protects against diet-induced obesity and its hepatic sequelae. Inhibition of HL-activity may therefore have value in the prevention and/or treatment of obesity.

Three novel IGFALS gene mutations resulting in total ALS and severe circulating IGF-I/IGFBP-3 deficiency in children of different ethnic origins.

BACKGROUND/AIMS: To date, four mutations in the IGFALS gene have been reported. We now describe two children of different ethnic background with total acid-labile subunit (ALS) and severe circulating IGF-I/IGFBP-3 deficiencies resulting from three novel mutations in the IGFALS gene. PATIENTS/METHODS: Serum and DNA of patients were analyzed. RESULTS: Case 1 is a 12-year-old boy of Mayan origin. Case 2 is a 5-year-old girl of Jewish/Eastern European (Polish, Russian, Austrian-Hungarian)/Icelandic/European (French, English) ancestry. The reported cases had moderate short stature (-2.91 and -2.14 SDS, respectively), nondetectable serum ALS and extremely low serum concentrations of IGF-I and IGFBP-3. Case 1 harbored a novel homozygous 1308_1316 dup9 mutation in a highly conserved leucine-rich repeat (LRR) 17 motif of exon 2, representing an in-frame insertion of 3 amino acids, LEL. Case 2 harbored a novel heterozygous C60S/L244F mutation in exon 2, located within a highly conserved LRR 1 and LRR 9, respectively. CONCLUSIONS: The identification of additional novel IGFALS mutations, resulting in severe IGF-I/IGFBP-3 and ALS deficiencies, supports IGFALS as a candidate gene of the GH/IGF system, implicated in the pathogenesis of primary IGF deficiency, and represents an important part of its differential diagnosis.

Remission of congenital diabetes insipidus after eight years.

Septo-optic dysplasia (SOD) (De Morsier's syndrome) is a complex developmental disorder marked by variable and often incomplete formation of cranial midline structures, resulting in absence of the septum pellucidum, optic nerve hypoplasia, and hypothalamic-pituitary dysfunction. We describe a patient with SOD who manifested symptoms in the early neonatal period with severe deficiencies of multiple pituitary hormones including anti-diuretic hormone (ADH). Her congenital diabetic insipidus (DI), consequence of an anatomic defect, can be argued to be of the most severe type. Our patient resolved her severe DI 8 years after her initial presentation, suddenly requiring no further medical treatment for DI following longstanding pharmacological replacement of ADH. This is the first report of a patient with SOD with spontaneous resolution of congenital DI.

Equivalent insulin resistance in latent autoimmune diabetes in adults (LADA) and type 2 diabetic patients.

Insulin resistance is a primary component in the pathophysiology of type 2 diabetes. In latent autoimmune diabetes in adults (LADA), insulin resistance has been reported to be significantly lower than in autoantibody-negative type 2 diabetes (T2DM), but whether this might be related to differences in body mass index (BMI) has not been excluded. Furthermore, previous studies have used limiting inclusive criteria for LADA, requiring only the presence of GADA or IA-2A. To apply more inclusive criteria for LADA, consistent with recent recommendations, we defined LADA by clinical manifestations characteristic of T2DM, but with the presence of any combination of GADA, IA-2A, ICA, or IAA. We recruited 43 LADA patients, 70 T2DM patients, and 150 non-diabetic controls. Insulin resistance was assessed by both the homeostasis model assessment and the quantitative insulin sensitivity check index, and BMI was calculated. We found that insulin resistance in LADA is equivalent to that of T2DM. When insulin resistance is assessed as a function of BMI, both diabetic populations demonstrated an insulin resistance equally greater than normal controls. The interaction between insulin resistance and BMI in the two diabetic groups was significantly different from that demonstrated in non-diabetic controls. In summary, LADA demonstrates insulin resistance of similar magnitude to T2DM, but with the concurrent component of an immune attack against the pancreatic beta-cells. LADA patients may be at significant risk for metabolic consequences of insulin resistance other than glucose metabolism, such as those described in the metabolic syndrome. As complications and treatment regimens specific to LADA are realized, improved means of identification of LADA will become increasingly important.

Diabetic neuropathy, the great masquerader: truncal neuropathy manifesting as abdominal pseudohernia.

OBJECTIVE: To describe a patient with diabetic truncal neuropathy and suggest a helpful diagnostic approach to this entity. METHODS: We present a case report, with a focus on physical, computed tomographic, and electromyographic findings. RESULTS: Because of an extensive differential diagnosis, diabetic truncal neuropathy is a rarely recognized and often misdiagnosed condition in patients with diabetes mellitus. In a 55-year-old man with a 13-year history of diabetes but no retinopathy, vasculopathy, or nephropathy, pain and a visible bulge in the left lower abdominal quadrant prompted radiographic assessment of the abdomen. A computed tomographic scan of the abdomen disclosed no mass but a weakening of the abdominal musculature suggestive of a pseudohernia. Subsequent electromyography showed evidence of polyradicular neuropathy. The patient was given treatment for pain control, and the pseudohernia resolved within 1 year. CONCLUSION: In patients with diabetes who have a painful abdominal mass, the potential presence of a diabetic truncal neuropathy should be considered.

Onset of acquired autoimmune hypothyroidism in infancy: a presentation of delayed gross-motor development and rhabdomyolysis.

We report the case of a 23-month-old girl who presented with poor growth and delayed attainment of gross-motor milestones. Elevated creatine phosphokinase (CPK) indicated rhabdomyolysis, ultimately attributed to severe, acquired autoimmune hypothyroidism. Growth data and bone-age suggest the onset of hypothyroidism occurred at or before 12 months of age. Acquired hypothyroidism is rare before age 3 years, and rhabdomyolysis due to hypothyroidism has not previously been reported as a cause of delayed gross-motor development in toddlerhood. Despite the early onset of hypothyroidism, cognitive function appeared to be unaffected. Adequate thyroid hormone replacement quickly normalized the CPK in our patient, and gross motor development rapidly improved. Although rare, rhabdomyolysis secondary to hypothyroidism should be in the differential diagnosis of delayed gross-motor development in infancy and toddlerhood.