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

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

Iodine fortification may influence the age-related change in thyroid volume: a longitudinal population-based study (DanThyr).

ObjectiveTo assess the individuals' thyroid volume changes after the mandatory nationwide iodine fortification (IF) program in two Danish areas with different iodine intake at baseline (Copenhagen, mild iodine deficiency (ID) and Aalborg, moderate ID).DesignA longitudinal population-based study (DanThyr).MethodsWe examined 2465 adults before (1997) and after (2008) the Danish IF of salt (2000). Ultrasonography was carried out by the same sonographers using the same equipment, after controlling performances. Participants treated for thyroid disease were excluded from analyses.ResultsOverall, median thyroid volume had increased in Copenhagen (11.8–12.2 ml, P=0.001) and decreased in Aalborg, although not significantly (13.3–13.1 ml, P=0.07) during the 11 years of follow-up.In both regions, there was an age-related trend in individual changes in thyroid volume from baseline to follow-up; thyroid volume increased in women &lt;40 years of age and decreased in women &gt;40 years of age.In a multivariate regression model, higher age at entry was a predictor (P&lt;0.05) for thyroid volume decrease &gt;20% during the follow-up period (women aged 40–45 years: odds ratio (OR) 4.3 (95% CI, 2.2–8.2); women aged 60–65 years: 5.8 (2.9–11.6)) and individuals of higher age were also less likely to have an increase in thyroid volume (women aged 40–45 years: OR 0.2 (0.1–0.3); women aged 60–65: OR 0.3 (0.2–0.4)).ConclusionsAge-dependent differences in thyroid volume and enlargement had leveled out after the Danish iodization program. Thus, the previously observed increase in thyroid volume with age may have been caused by ID.</jats:sec

Serum thyroglobulin before and after iodization of salt:an 11-year DanThyr follow-up study

ObjectiveOur objective was to investigate individual serum thyroglobulin (Tg) changes in relation to iodine fortification (IF) and to clarify possible predictors of these changes.DesignWe performed a longitudinal population-based study (DanThyr) in two regions with different iodine intake at baseline: Aalborg (moderate iodine deficiency (ID)) and Copenhagen (mild ID). Participants were examined at baseline (1997) before the mandatory IF of salt (2000) and again at follow-up (2008) after IF.MethodsWe examined 2465 adults and a total of 1417 participants with no previous thyroid disease and without Tg-autoantibodies were included in the analyses. Serum Tg was measured by immunoradiometric method. We registered participants with a daily intake of iodine from supplements in addition to IF.ResultsOverall, the follow-up period saw no change in median Tg in Copenhagen (9.1/9.1 μg/l,P=0.67) while Tg decreased significantly in Aalborg (11.4/9.0 μg/l,P&lt;0.001). Regional differences were evident before IF (Copenhagen/Aalborg, 9.1/11.4 μg/l,P&lt;0.001), whereas no differences existed after IF (9.1/9.0 μg/l,P=1.00). Living in Aalborg (P&lt;0.001) and not using iodine supplements at baseline (P=0.001) predicted a decrease in Tg whereas baseline thyroid enlargement (P=0.02) and multinodularity (P=0.01) were associated with an individual increase in Tg during follow-up.ConclusionsAfter IF we observed a decrease in median Tg in Aalborg and the previously observed regional differences between Aalborg and Copenhagen had levelled out. Likewise, living in Aalborg was a strong predictor of an individual decrease in serum Tg. Thus, even small differences in iodine intake at baseline were very important for the individual response to IF.</jats:sec

Low-volume, high-intensity interval training rapidly improves cardiopulmonary function in post-menopausal women

Objective: This study compared the effects of a 2-week program of low-volume high-intensity interval training (HIT) with the effects of higher-volume moderate-intensity continuous training (CT) on cardiopulmonary and vascular functions in postmenopausal women. Methods: Twenty-two postmenopausal women were randomly assigned to undertake six HIT (n = 12) or CT (n = 10) sessions for 2 weeks. HIT sessions consisted of ten 1-minute intervals of cycling exercise at 100% of peak power output separated by 1 minute of active recovery. CT sessions involved 40 minutes of continuous cycling at 65% of peak power output. Variables assessed at baseline and 2 weeks included cardiopulmonary function (ventilatory threshold, peak oxygen uptake), macrovascular endothelial function (flow-mediated dilation of the brachial artery), and microvascular function (reactive hyperemia and local thermal hyperemia of forearm skin). Results: Eighteen participants completed the study (HIT, 11; CT, 7). Adherence to the exercise programs was excellent, with 107 of 108 sessions completed. Despite substantially lower total time commitment (~2.5 vs ~5h) and training volume (558 vs 1,237 kJ) for HIT versus CT, increases from baseline in peak oxygen uptake achieved significance (P = 0.01) for the HIT group only ([DELTA = 2.2 mL kg-1 min -1; P for interaction = 0.688). Improvements in exercise test duration were observed in both groups (HIT, 13%; CT, 5%; P for interaction = 0.194). There were no significant changes in macrovascular or microvascular function in either group. Conclusions: The findings suggest that low-volume HIT is feasible and can lead to rapid improvements in cardiopulmonary function in postmenopausal women.</p