Influence of Ultraviolet Radiation on the Association between 25-Hydroxy Vitamin D Levels and Cardiovascular Risk Factors in Obesity.

OBJECTIVE: To establish if the correction with estimates of ultraviolet (UV) exposure influences the association between 25-OH-vitamin D (25OHD) levels and metabolic variables. STUDY DESIGN: A cross-sectional study was performed in 575 obese children and adolescents (>6 years of age) in a tertiary referral center. Cardiovascular risk factors were measured. The estimate of UV exposure was evaluated by 3 methods: (1) season; (2) mean of UV radiation (UVR); and (3) mean of UV index (UVI). UVR and UVI were considered at 1 (UVR 1 month prior to testing [UVR1], UVI 1 month prior to testing [UVI1]) or 3 (UVR 3 months prior to testing [UVR3], UVI 3 months prior to testing [UVI3]) months prior to testing. All analyses were corrected for confounders (sex, age, puberty, body mass index, waist circumference, the inclusion and exclusion of estimates of UV exposure). RESULTS: The 25OHD levels were associated with seasons, UVR1, UVR3, UVI1, and UVI3, and best associations with UVR3 and UVI3. In all models, total cholesterol, low-density lipoprotein cholesterol and triglycerides were negatively associated with 25OHD levels. The strength of the association increased with no correction, correction for seasons, UVR, and UVI. UVR3 and UVI3 performed better than UVR1 and UVI3. CONCLUSIONS: Higher lipid concentrations were associated with low 25OHD levels in obese children and adolescents with the power of the association dependent on the estimates of UVR. As the mean values 3 months prior to testing for both UVR and UVI determined the best associations, the interval of the steady state time of 25OHD levels could be preferentially used in the metabolic studies. Controlling for an estimate of UVR is important to decrease the heterogeneity of studies.

Serum thyrotropin concentration in children with isolated thyroid nodules.

OBJECTIVE: To investigate the correlation between serum thyroid-stimulating hormone (TSH) concentration and nodule nature in pediatric patients with thyroid nodules, with the aim of identifying a marker able to differentiate benign and malignant nodules. STUDY DESIGN: This was a retrospective analysis of serum TSH concentrations in a multicentric case series of 125 pediatric patients with benign and malignant thyroid nodules. RESULTS: Of the 125 patients, 99 had benign thyroid nodules and 26 had differentiated thyroid cancer (24 papillary and 2 follicular). Final diagnosis was based on surgery in 57 cases and on a benign cytology plus clinical follow-up in 68 cases. Serum TSH concentration was significantly higher in patients with thyroid cancer compared with those with benign nodules (3.23 ± 1.59 mU/L vs 1.64 ± 0.99 mU/L; P < .001). Binary logistic regression analysis revealed that serum TSH was the sole predictor of malignancy (P < .001). Dividing the patient cohort into 5 groups based on serum TSH quintiles (TSH cutoffs 0.40, 1.00, 1.50, 1.80, and 2.80 mU/L), we observed that cancer prevalence increased in parallel with serum TSH (P < .001), with respective rates of 0%, 4%, 16%, 32%, and 52% in the 5 quintile groups. CONCLUSION: Because cases with malignant nodules are most likely seen in the upper normal serum TSH range (ie, >2.8 mU/L), serum TSH concentration can serve as a predictor of thyroid cancer in pediatric patients with thyroid nodules and can inform the decision of when to submit patients to further investigation by cytology.

The natural history of euthyroid Hashimoto's thyroiditis in children.

OBJECTIVE: To study the natural history of Hashimoto's thyroiditis (HT) in children and identify factors predictive of thyroid dysfunction. STUDY DESIGN: We evaluated 160 children (43 males and 117 females, mean age 9.10 +/- 3.6 years, with HT and normal (group 0; 105 patients) or slightly elevated (group 1; 55 patients) serum thyroid-stimulating hormone (TSH) concentrations. The patients were assessed at presentation and then followed for at least 5 years if they remained euthyroid or if their TSH did not rise twofold over the upper normal limit. RESULTS: At baseline, age, sex, thyroid volume, free thyroxine, free triiodothyronine, thyroid peroxidase antibody (TPOab), and thyroglobulin antibody (TGab) serum concentrations were similar in the 2 groups. During follow-up, 68 patients of group 0 remained euthyroid, and 10 patients moved from group 0 to group 1. In 27 patients, TSH rose twofold above the upper normal limit (group 2), and 9 of these patients developed overt hypothyroidism. Sixteen patients of group 1 ended up in group 0, 16 remained in group 1, and 23 moved to group 2. A comparison of the data of the patients who maintained or improved their thyroid status with those of the patients whose thyroid function deteriorated revealed significantly increased TGab levels and thyroid volume at presentation in the latter group. However, none of these parameters alone or in combination were of any help in predicting the course of the disease in a single patient. CONCLUSIONS: The presence of goiter and elevated TGab at presentation, together with progressive increase in both TPOab and TSH, may be predictive factors for the future development of hypothyroidism. At 5 years of follow-up, more than 50% of the patients remained or became euthyroid.