Thyroid Function and Body Weight: A Community-Based Longitudinal Study

OBJECTIVE: Body weight and overt thyroid dysfunction are associated. Cross-sectional population-based studies have repeatedly found that thyroid hormone levels, even within the normal reference range, might be associated with body weight. However, for longitudinal data, the association is less clear. Thus, we tested the association between serum thyrotropin (TSH) and body weight in a community-based sample of adult persons followed for 11 years. METHODS: A random sample of 4,649 persons aged 18-65 years from a general population participated in the DanThyr study in 1997-8. We included 2,102 individuals who participated at 11-year follow-up, without current or former treatment for thyroid disease and with measurements of TSH and weight at both examinations. Multiple linear regression models were used, stratified by sex and adjusted for age, smoking status, and leisure time physical activity. RESULTS: Baseline TSH concentration was not associated with change in weight (women, P = 0.17; men, P = 0.72), and baseline body mass index (BMI) was not associated with change in TSH (women, P = 0.21; men, P = 0.85). Change in serum TSH and change in weight were significantly associated in both sexes. Weight increased by 0.3 kg (95% confidence interval [CI] 0.1, 0.4, P = 0.005) in women and 0.8 kg (95% CI 0.1, 1.4, P = 0.02) in men for every one unit TSH (mU/L) increase. CONCLUSIONS: TSH levels were not a determinant of future weight changes, and BMI was not a determinant for TSH changes, but an association between weight change and TSH change was present

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Thyroid Nodules in an 11-Year DanThyr Follow-Up Study

Context: Limited longitudinal data are available on changes in the thyroid gland structure in a population and how this is influenced by iodine fortification (IF). Objective: Our objective was to clarify how IF influenced thyroid gland structure in 2 regions with different iodine intake at baseline (Copenhagen, mild iodine deficiency [ID]; Aalborg, moderate ID). Design and Setting: We conducted a longitudinal population-based study (DanThyr) where participants were examined before (1997) and after (2008) the Danish mandatory IF of salt (2000). Participants: We examined 2465 adults, and ultrasonography was performed by the same sonographers using the same equipment, after controlling performances. Main Outcome Measure: Change in thyroid gland structure was evaluated. Results: The follow-up period saw an increased prevalence of multinodularity (9.8%–13.8 %, P &amp;lt; .001), especially in the previously moderate ID region of Aalborg (9.1%–15.4%, P &amp;lt; .001), whereas no change in prevalence was seen for solitary nodules (5.6%–5.1%, P = .34). In individual participants, changes in thyroid structure and disappearance of thyroid nodules during the 11 years was common with an overall normalization rate of 21.2 (95% confidence interval [CI] = 17.9–24.9) per 1000 person-years. Solitary nodules had a significantly higher normalization rate than multiple nodules (normalization rate ratio 0.47 [95% CI = 0.32–0.67]). A regional difference (Aalborg vs Copenhagen) was seen between normalization rates of multiple nodules (normalization rate ratio 0.29 [95% CI = 0.12–0.64]), but not for solitary nodules (normalization rate ratio 0.81 [95% CI = 0.53–1.21]). Conclusions: Changes in the thyroid gland structure with both appearance and disappearance of thyroid nodules are common after an iodization program. </jats:sec