Thyrotropin and free triiodothyronine concentrations are associated to weight loss in lifestyle intervention and weight regain afterwards in obese children.

B Wolters, Pediatric Endocrinology, Vestische Kinderklinik, Datteln, Germany.
European Journal of Endocrinology (Impact Factor: 3.69). 12/2012; DOI: 10.1530/EJE-12-0981
Source: PubMed

ABSTRACT OBJECTIVE: The impact of thyroid hormones on weight loss in lifestyle interventions and on weight regain afterwards is unknown. Therefore, we studied the relationships between thyrotropin (TSH), free triiodothyronine (fT3), free thyroxine (fT4) and weight status, as well as their changes during and after a lifestyle intervention in obese children. MATERIAL AND METHODS: We evaluated the weight status as BMI-SDS in 477 obese children (age 10.6±2.7 years, 46% male, BMI 28.1±4.5kg/m&sup2;) participating in a 1-year lifestyle intervention in a 2-year longitudinal study. Changes of BMI-SDS at 1 and 2 years were correlated to TSH, fT3, and fT4 concentrations at baseline and their changes during intervention. RESULTS: The decrease of BMI-SDS in the intervention period (-0.32±0.38;p<0.001) was significantly positively associated to baseline TSH and fT3 in multiple linear regression analyses adjusted to age, gender, pubertal stage, and baseline BMI-SDS. The increase of BMI-SDS after end of intervention (+0.05±0.36;p=0.011) was significantly related to the decreases of TSH and fT3 during the intervention in multiple linear regression analyses adjusted to change of BMI-SDS during intervention. In contrast to children with weight maintenance, children with weight regain after end of intervention demonstrated a decrease of their TSH (-0.1±1.6 versus +0.2±1.6mU/l;p=0.03) and fT3 (-0.2±1.1 versus +0.3±1.6pg/ml;p<0.001) levels during intervention. CONCLUSIONS: The decreases of TSH and fT3 concentrations during lifestyle intervention were associated to weight regain after intervention. Future studies should confirm that the decreases of TSH and fT3 levels in weight loss are related to change of metabolisms such as resting energy expenditure.

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    ABSTRACT: Objective: An elevated thyroid stimulating hormone (TSH) level is a frequent finding in obese children, but its association with peripheral hormone metabolism is not fully understood. We hypothesized that in obesity, the changes in thyroid hormone metabolism in peripheral tissues might lead to dysregulation in the thyroid axis. The purpose of this study was to investigate the association of TSH with thyroid hormones in a group of obese children as compared to normal-weight controls. Methods: Serum TSH, free thyroxine (fT4) and free triiodothyronine (fT3) levels were measured in 101 obese children and in 40 controls. Serum reverse T3 (rT3) levels were also measured in a subgroup of 51 obese children and in 15 controls. Results: Serum TSH level was significantly higher in obese children compared to controls (2.78 vs. 1.99 mIU/L, p<0.001), while no difference was found in fT4, fT3, rT3 levels and in fT3/rT3 ratio. In the obese group, fT3 level positively correlated with fT4 (r=0.217, p=0.033) and inversely with rT3 (r=-0.288, p=0.045). However, thyroid hormone levels and TSH levels were not correlated. Conclusion: In obese children, normal fT4, fT3 and rT3 levels suggest an undisturbed peripheral hormone metabolism. These levels show no correlation with elevated TSH levels.
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    ABSTRACT: Subclinical hypothyroidism (SCH) should be considered in two categories according to the elevation in serum thyroid-stimulating hormone (TSH) level: mildly increased TSH levels (4.0-10.0 mU/l) and more severely increased TSH value (>10 mU/l). An initially raised serum TSH, with FT4 within reference range, should be investigated with a repeat measurement of both serum TSH and FT4, along with thyroid peroxidase antibodies, preferably after a 2- to 3-month interval. Even in the absence of symptoms, replacement therapy with L-thyroxine is recommended for younger patients (<65-70 years) with serum TSH >10 mU/l. In younger SCH patients (serum TSH <10 mU/l) with symptoms suggestive of hypothyroidism, a trial of L-thyroxine replacement therapy should be considered. For such patients who have been started on L-thyroxine for symptoms attributed to SCH, response to treatment should be reviewed 3 or 4 months after a serum TSH within reference range is reached. If there is no improvement in symptoms, L-thyroxine therapy should generally be stopped. Age-specific local reference ranges for serum TSH should be considered in order to establish a diagnosis of SCH in older people. The oldest old subjects (>80-85 years) with elevated serum TSH ≤10 mU/l should be carefully followed with a wait-and-see strategy, generally avoiding hormonal treatment. If the decision is to treat SCH, then oral L-thyroxine, administered daily, is the treatment of choice. The serum TSH should be re-checked 2 months after starting L-thyroxine therapy, and dosage adjustments made accordingly. The aim for most adults should be to reach a stable serum TSH in the lower half of the reference range (0.4-2.5 mU/l). Once patients with SCH are commenced on L-thyroxine treatment, then serum TSH should be monitored at least annually thereafter.
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