The impact of thyroid hormones on weight loss in lifestyle interventions and on weight regain afterwards is unknown. Therefore, we studied the relationships between TSH, free triiodothyronine (fT₃), free thyroxine (fT₄), and weight status, as well as their changes during and after a lifestyle intervention in obese children.
Materials and methods:
We evaluated the weight status as BMI-SDS in 477 obese children (mean age 10.6±2.7 years, 46% male, mean BMI 28.1±4.5 kg/m²) participating in a 1-year lifestyle intervention in a 2-year longitudinal study. Changes in BMI-SDS at 1 and 2 years were correlated with TSH, fT₃, and fT₄ concentrations at baseline and their changes during the intervention.
A decrease in BMI-SDS during the intervention period (-0.32±0.38; P<0.001) was significantly positively associated with baseline TSH and fT₃ in multiple linear regression analyses adjusted for age, sex, pubertal stage, and baseline BMI-SDS. An increase in BMI-SDS after the end of the intervention (+0.05±0.36; P=0.011) was significantly related to the decreases in TSH and fT₃ during the intervention in multiple linear regression analyses adjusted for change in BMI-SDS during the intervention. In contrast to children with weight maintenance, children with weight regain after the end of the intervention demonstrated a decrease in their TSH levels (-0.1±1.6 vs +0.2±1.6 mU/l; P=0.03) and fT₃ (-0.2±1.1 vs +0.3±1.6 pg/ml; P<0.001) during the intervention.
The decreases in TSH and fT₃ concentrations during the lifestyle intervention were associated with weight regain after the intervention. Future studies should confirm that the decreases in TSH and fT₃ levels associated with weight loss are related to the change in metabolism such as resting energy expenditure.
"Since rapid weight loss is associated with a decrease in both TSH and T3 levels, the resulting decrease in resting energy expenditure (REE) may contribute towards the difficulties maintaining weight loss (6,22). This theory is supported by the results of Wolters et al (25) which indicate that the decrease in TSH and fT3 concentrations during lifestyle intervention is associated with weight regain after the intervention. "
[Show abstract][Hide abstract] 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.
Journal of Clinical Research in Pediatric Endocrinology 06/2014; 6(2):100-104. DOI:10.4274/Jcrpe.1251
[Show abstract][Hide abstract] 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.
European Thyroid Journal 12/2013; 2(4):215-228. DOI:10.1159/000356507
[Show abstract][Hide abstract] ABSTRACT: This guideline has been produced as the official statement of the European Thyroid Association guideline committee. Subclinical hypothyroidism (SCH) in pregnancy is defined as a thyroid-stimulating hormone (TSH) level above the pregnancy-related reference range with a normal serum thyroxine concentration. Isolated hypothyroxinaemia (defined as a thyroxine level below the 2.5th centile of the pregnancy-related reference range with a normal TSH level) is also recognized in pregnancy. In the majority of SCH the cause is autoimmune thyroiditis but may also be due to iodine deficiency. The cause of isolated hypothyroxinaemia is usually not apparent, but iodine deficiency may be a factor. SCH and isolated hypothyroxinaemia are both associated with adverse obstetric outcomes. Levothyroxine therapy may ameliorate some of these with SCH but not in isolated hypothyroxinaemia. SCH and isolated hypothyroxinaemia are both associated with neuro-intellectual impairment of the child, but there is no evidence that maternal levothyroxine therapy improves this outcome. Targeted antenatal screening for thyroid function will miss a substantial percentage of women with thyroid dysfunction. In children SCH (serum TSH concentration >5.5-10 mU/l) normalizes in >70% and persists in the majority of the remaining patients over the subsequent 5 years, but rarely worsens. There is a lack of studies examining the impact of SCH on the neuropsychological development of children under the age of 3 years. In older children, the evidence for an association between SCH and impaired neuropsychological development is inconsistent. Good quality studies examining the effect of treatment of SCH in children are lacking.
European Thyroid Journal 06/2014; 3(2):76-94. DOI:10.1159/000362597
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