Weight gain following treatment of hyperthyroidism

Effect of Feeding an Iodine-Restricted Diet in Cats with Spontaneous Hyperthyroidism

BACKGROUND

Exclusive feeding of an iodine-restricted diet has been proposed as a method for controlling clinical manifestations of hyperthyroidism in hyperthyroid cats.

OBJECTIVES

To determine the effect of feeding an iodine-restricted diet on TT4 concentrations and clinical signs in cats with spontaneous hyperthyroidism.

ANIMALS

Forty-nine client-owned cats with spontaneous hyperthyroidism.

METHODS

Retrospective case series. Hyperthyroid cats were exclusively fed a commercially available iodine-restricted diet. Clinical response was assessed by change in weight and heart rate and serum TT4, blood urea nitrogen (BUN), and creatinine concentrations at various times during dietary management (21-60 days, 60-180 days).

RESULTS

Serum TT4 normalized in 20/48 cats (42%) and 39/47 cats (83%) at 21-60 days and 61-180 days, respectively. Cats in which the TT4 concentrations were still above reference range at 21-60 days had a significantly higher starting TT4 than those that normalized their TT4 levels during the same time period (P = .038). Body weight did not significantly increase (P = .34) nor heart rate decrease (P = .64) during the study. There was a significant decrease in serum creatinine (P = .028). Cats in the low reference range for serum TT4 concentrations did not have a significant increase in body weight (P = .41) nor creatinine (P = .54) when compared to those with high reference range.

CONCLUSIONS AND CLINICAL IMPORTANCE

Restricted-iodine diets were effective at maintaining serum TT4 concentrations within reference ranges for a majority of cats with spontaneous hyperthyroidism over 1 year, although not all clinical signs of hyperthyroidism improved.

Relationship between indices of obesity obtained by anthropometry and dual-energy X-ray absorptiometry: The Fourth and Fifth Korea National Health and Nutrition Examination Survey (KNHANES IV and V, 2008-2011)

BACKGROUND

Body mass index (BMI), waist circumference (WC), and even dual-energy X-ray absorptiometry (DXA) are used for obesity diagnosis. However, it is not known which DXA-derived index of obesity correlates best with BMI and/or WC and it is not clear whether such an index is accurate or not.

OBJECTIVES

The aim of this study is to show the relationship between anthropometric measurements (BMI, WC) and body fat indices from DXA and to determine which DXA indices are strongly related to BMI and WC.

SUBJECTS

This study was based on data obtained from the Fourth and Fifth Korea National Health and Nutrition Examination Survey (KNHANES IV-V). DXA measurements were performed on survey subjects over 10 years old from July 2008 through to May 2011. Of these, 18 198 individuals, aged 19 years and older for whom DXA data were available, were included.

METHODS

Weighted Pearson's correlated coefficients (r) were calculated among indices, according to sex, age group and menopause, and the coefficients were compared with each other.

RESULTS

BMI correlates most with trunk body fat mass in kg (r=0.831) and then with total body fat in kg (r=0.774, P<0.00043 for difference of r). In the older age group, BMI correlates with total body fat mass (r=0.822) better than with trunk fat mass (r=0.817, P<0.00043). WC correlates with trunk body fat mass most in both genders and all age groups (0.804≤r≤0.906). Correlations of BMI (r=0.645 for men, 0.689 for women) and WC (r=0.678 for men, 0.634 for women) to body fat percentages (%) were less robust than those to body fat mass.

CONCLUSIONS

BMI and WC reflect trunk and total body fat in kg more than body fat percentage derived by DXA.

Changes in body weight after treatment of primary hypothyroidism with levothyroxine

OBJECTIVE

Surprisingly few studies have examined weight change in hypothyroid patients after initiation of levothyroxine (LT4) therapy. Our study aimed to investigate weight change after initiation of LT4 treatment for primary hypothyroidism.

METHODS

Using electronic medical records from Boston Medical Center, Boston, Massachusetts, we performed a retrospective cohort study between January 1, 2003, and February 1, 2011. Adults ≥18 years of age with newly diagnosed primary hypothyroidism with an initial thyroid-stimulating hormone (TSH) level ≥10 mIU/L were identified. Patients with postsurgical hypothyroidism, thyroid cancer, and a history of radioactive iodine or head/neck irradiation, congestive heart failure, anorexia nervosa, end-stage renal disease, cirrhosis, pregnancy, or use of prescription weight-loss medications were excluded. TSH and weight at diagnosis and up to 24 months after LT4 initiation were collected. Weight change was assessed at the first posttreatment serum TSH level <5 mIU/L.

RESULTS

A total of 101 patients (mean age, 48 ± 15 years; 71% women) were included. Initial median TSH was 18.3 mIU/L (range, 10.1 to 710.5 mIU/L) and initial median weight was 79.6 kg (range 41.5 to 167.5 kg). Posttreatment median TSH level was 2.3 mIU/L (range, 0.04 to 5 mIU/L), and weight change at a median of 5 months (range, 1.1 to 25.6 months) was -0.1 kg (range, -20.6 to 7.7 kg). Initial median body mass index (BMI) of 95 of the patients was 29.3 kg/m2 (range, 19.5 to 56.1 kg/m2), and the median change in BMI was -0.1 kg/m2 (range, -7.1 to 3.3 kg/m2). Only 52% of patients lost weight, with a mean weight loss of 3.8 ± 4.4 kg. Gender, race, education, insurance type, age, initial TSH level, time to normalization of TSH, and initial weight were not associated with changes in weight or BMI.

CONCLUSION

Contrary to popular belief, our study of 101 patients with primary hypothyroidism showed that no significant weight change occurs after initiation of LT4 treatment.

A thyroid hormone challenge in hypothyroid rats identifies T3 regulated genes in the hypothalamus and in models with altered energy balance and glucose homeostasis

BACKGROUND

The thyroid hormone triiodothyronine (T3) is known to affect energy balance. Recent evidence points to an action of T3 in the hypothalamus, a key area of the brain involved in energy homeostasis, but the components and mechanisms are far from understood. The aim of this study was to identify components in the hypothalamus that may be involved in the action of T3 on energy balance regulatory mechanisms.

METHODS

Sprague Dawley rats were made hypothyroid by giving 0.025% methimazole (MMI) in their drinking water for 22 days. On day 21, half the MMI-treated rats received a saline injection, whereas the others were injected with T3. Food intake and body weight measurements were taken daily. Body composition was determined by magnetic resonance imaging, gene expression was analyzed by in situ hybridization, and T3-induced gene expression was determined by microarray analysis of MMI-treated compared to MMI-T3-injected hypothalamic RNA.

RESULTS

Post mortem serum thyroid hormone levels showed that MMI treatment decreased circulating thyroid hormones and increased thyrotropin (TSH). MMI treatment decreased food intake and body weight. Body composition analysis revealed reduced lean and fat mass in thyroidectomized rats from day 14 of the experiment. MMI treatment caused a decrease in circulating triglyceride concentrations, an increase in nonesterified fatty acids, and decreased insulin levels. A glucose tolerance test showed impaired glucose clearance in the thyroidectomized animals. In the brain, in situ hybridization revealed marked changes in gene expression, including genes such as Mct8, a thyroid hormone transporter, and Agrp, a key component in energy balance regulation. Microarray analysis revealed 110 genes to be up- or downregulated with T3 treatment (± 1.3-fold change, p<0.05). Three genes chosen from the differentially expressed genes were verified by in situ hybridization to be activated by T3 in cells located at or close to the hypothalamic ventricular ependymal layer and differentially expressed in animal models of long- and short-term body weight regulation.

CONCLUSION

This study identified genes regulated by T3 in the hypothalamus, a key area of the brain involved in homeostasis and neuroendocrine functions. These include genes hitherto not known to be regulated by thyroid status.

Mechanisms in endocrinology: the crosstalk between thyroid gland and adipose tissue: signal integration in health and disease

Obesity and thyroid diseases are common disorders in the general population and they frequently occur in single individuals. Alongside a chance association, a direct relationship between 'thyroid and obesity' has been hypothesized. Thyroid hormone is an important determinant of energy expenditure and contributes to appetite regulation, while hormones and cytokines from the adipose tissue act on the CNS to inform on the quantity of energy stores. A continuous interaction between the thyroid hormone and regulatory mechanisms localized in adipose tissue and brain is important for human body weight control and maintenance of optimal energy balance. Whether obesity has a pathogenic role in thyroid disease remains largely a matter of investigation. This review highlights the complexity in the identification of thyroid hormone deficiency in obese patients. Regardless of the importance of treating subclinical and overt hypothyroidism, at present there is no evidence to recommend pharmacological correction of the isolated hyperthyrotropinemia often encountered in obese patients. While thyroid hormones are not indicated as anti-obesity drugs, preclinical studies suggest that thyromimetic drugs, by targeting selected receptors, might be useful in the treatment of obesity and dyslipidemia.

Association between thyroid hormones and body fat in euthyroid subjects

OBJECTIVE

Thyroid hormones disorders are associated with changes of body composition. However, the relationship between thyroid hormones and body fat in a euthyroid population is unclear. The aim of this study was to explore the association between thyroid hormones and body fat in a euthyriod population.

SUBJECTS

A total of 865 euthyroid individuals were recruited in this study. Subjects with thyroid diseases or diabetes and who were taking medications that could influence thyroid hormones, weight or glucose metabolism were excluded.

MEASUREMENTS

FT3, FT4, lipid parameters, fasting insulin (FINS) and blood glucose were determined, and homeostasis model assessment for insulin resistance (HOMA-IR) was calculated. Anthropometric measurements were taken, and body fat parameters were assessed.

RESULTS

Serum FT3 was slightly higher in body mass index (BMI) ≥25 kg/m(2) group than that in BMI <25 kg/m(2) group (P < 0·05). However, the difference was too small to have clinical significance. FT4 levels were not significantly different between the two groups. Body weight, BMI, waist circumference, hip circumference, waist-to-hip ratio (WHR), percentage of body fat (PBF), waist-fat-to-hip-fat ratio, FINS and HOMA-IR increased linearly with the elevation of FT3 adjusted for age and gender. A multivariate linear regression analysis revealed that fat mass, PBF, HOMA-IR and FT4 contributed significantly to FT3 levels.

CONCLUSION

Grouped according to BMI, overweight and obese subjects have similar thyroid hormones compared to those with normal weight. Body composition parameters increase with the elevation of FT3, and FT3 is associated with body fat parameters in euthyroid subjects.

Thyroidectomy as primary treatment optimizes body mass index in patients with hyperthyroidism

OBJECTIVE

The purpose of this study was to determine how the timing of thyroidectomy influenced postoperative weight change.

METHODS

We conducted a two-institution study, identifying patients treated with total thyroidectomy for hyperthyroidism. Patients were classified as 'early' if they were referred for surgery as the first treatment option, or 'delayed' if they were previously treated with radioactive iodine (RAI). Groups were compared with the Student's t-test or χ (2) test where appropriate.

RESULTS

There were 204 patients undergoing thyroidectomy for hyperthyroidism. Of these, 171 patients were classified as early and 33 were classified as delayed. Overall, patients gained 6.0 % ± 0.8 of their preoperative body weight at last follow-up. Preoperative body mass indexes (BMIs) were similar between groups (p = 0.98), and the median follow-up time was 388 days (range 15-1,584 days). Both groups gained weight until they achieved a normal thyroid-stimulating hormone (TSH) postoperatively. After achieving a normal TSH, the early group stabilized or lost weight (-0.2 lbs/day), while the delayed group continued to gain weight (0.02 lbs/day; p = 0.61). At last follow-up, there were significantly more patients in the delayed group who increased their BMI category compared with the early group (42.4 vs. 21.6 %; p = 0.01). Twice as many patients in the delayed group moved up or into an unhealthy BMI category (overweight or obese) compared with the early group (39.4 vs. 19.3 %; p = 0.01).

CONCLUSIONS

Compared with patients initially treated with RAI, patients with hyperthyroidism who underwent surgery as the first treatment were less likely to become overweight or obese postoperatively.

Are plasma thyroid-stimulating hormone levels associated with degree of obesity and metabolic syndrome in euthyroid obese patients? A Turkish cohort study

We aimed to observe the association between degree of obesity and metabolic syndrome and plasma thyrotropin levels in obese, euthyroid Turkish patients. 947 obese and overweight patients who admitted to our outpatient clinic were assessed retrospectively. 150 healthy euthyroid cases were also recruited as the control group. Cases with metabolic syndrome were determined. Patients were divided into various subgroups as overweight, obese, morbid obese, men, and women. No statistical significance was determined when all the patients' and subgroups' plasma thyrotropin levels were compared to normal weight control group. No association was shown between the presence of metabolic syndrome and plasma thyrotropin levels for both all patients and subgroups. Also there was not any association between each component of metabolic syndrome and plasma thyrotropin levels. In conclusion, we did not found any significant association between plasma thyrotropin levels and obesity and metabolic syndrome in our euthyroid subjects.

Predictors of treatment failure, incipient hypothyroidism, and weight gain following radioiodine therapy for Graves' thyrotoxicosis

BACKGROUND

Following radioiodine ((131)I) therapy, both late recognition of hypothyroidism and treatment failure may result in adverse outcomes.

AIM

We sought to assess indicators of both incipient hypothyroidism and treatment failure following (131)I and determine factors predictive of weight gain.

SUBJECTS AND METHODS

Retrospective study of 288 patients receiving (131)I for treatment of Graves' thyrotoxicosis. Primary outcome measures were thyroid status and weight change at 1 yr following (131)I.

RESULTS

The treatment failure rate at 1 yr was 13.5%. Hypothyroidism developed in 80.9%, with 58.5% of patients having levels of free T4 (fT4) <6 pmol/l at diagnosis. Patients receiving thionamides before and after (131)I had significantly higher levels of treatment failure (23.3%) than those with no thionamide exposure (6.3%, p=0.003), but also had more active Graves' disease. Following (131)I, development of a detectable TSH or low-normal fT4 levels was not associated with recurrent thyrotoxicosis. Median weight gain was 5.3 kg, although patients with nadir fT4 levels <6 pmol/l gained an average 2 kg more than those with levels >6 pmol/l (p=0.05). The main predictor of weight gain was fT4 level immediately prior to treatment; those in the lowest tertile gained a median 3.1 kg whilst those in the highest tertile gained 7.4 kg (median difference 4.3 kg; 95% confidence interval: 2.5-6.2).

CONCLUSIONS

Marked hypothyroidism following (131)I is common and often occurs early. Simple biochemical parameters may help identify incipient hypothyroidism and potentially limit excess weight gain. Treatment failure is common in patients with severe thyrotoxicosis and in such cases larger doses of (131)I may be warranted.

Body composition and metabolic parameters are associated with variation in thyroid hormone levels among euthyroid young men

OBJECTIVE

Thyroid disorders affect metabolism and body composition. Existing literature has been conflicting on whether this is also the case for thyroid hormone levels within the euthyroid range. Therefore, we have investigated the relationship between thyroid hormone concentrations and body composition together with metabolic parameters in a population of healthy euthyroid men.

METHODS

Healthy male siblings (n=941, 25-45 years, median BMI 24.6) were recruited in a cross-sectional, population-based study; a history or treatment of thyroid disease and thyroid autoimmunity were exclusion criteria. Body composition and muscle cross-sectional area were assessed by dual-energy X-ray absorptiometry and peripheral quantitative computed tomography. Total (triiodothyronine (T(3); TT(3)) thyroxine and (T(4); TT(4))) and free thyroid hormones (FT(3) and FT(4)), TSH, and reverse T(3) (rT(3)) and thyroid-binding globulin (TBG) were determined using immunoassays.

RESULTS

BMI was positively associated with (F)T(3) (P<0.0001). Whole body fat mass displayed positive associations with TT(3) and with (F)T(4) and TBG (P≤0.0006). Positive associations were further observed between leptin and (F)T(3), TT(4), and TBG (P≤0.0002). Inverse associations between lean mass and muscle cross-sectional area and (F)T(3), (F)T(4), and TBG were observed (P≤0.0003). Higher levels of (F)T(3) and TBG were associated with lower insulin sensitivity, assessed by homeostatic model assessment of insulin resistance (IR; P≤0.0001). No associations between TSH and body composition or metabolic parameters were seen.

CONCLUSION

We show that a less favorable body composition (with higher fat and lower muscle mass and accompanying higher leptin concentrations) and IR are associated with higher thyroid hormone levels in healthy young men with well characterized euthyroidism.

Thyroid function and obesity

Important interaction exists between thyroid function, weight control, and obesity. Several mechanisms seem to be involved, and in studies of groups of people the pattern of thyroid function tests depends on the balance of obesity and underlying thyroid disease in the cohort studied. Obese people with a normal thyroid gland tend to have activation of the hypothalamic-pituitary-thyroid axis with higher serum TSH and thyroid hormones in serum. On the other hand, small differences in thyroid function are associated with up to 5 kg difference in body weight. The weight loss after therapy of overt hypothyroidism is caused by excretion of water bound in tissues (myxoedema). Many patients treated for hyperthyroidism experience a gain of more weight than they lost during the active phase of the disease. The mechanism for this excessive weight gain has not been fully elucidated. New studies on the relation between L-T3 therapy and weight control are discussed. The interaction between weight control and therapy of thyroid disease is important to many patients and it should be studied in more detail.

Avaliação do peso corporal em pacientes com doença de Graves durante o tratamento com metimazol

OBJETIVO: Avaliar a alteração de peso durante o tratamento do hipertiroidismo e correlacioná-la com IL-6 e TNF-alfa. SUJEITOS E MÉTODOS: Quarenta e dois pacientes foram incluídos. Peso corporal (PC), índice de massa corpórea (IMC), características clínicas e laboratoriais foram registrados. IL-6 e TNF-alfa foram determinados antes do tratamento com metimazol (MMI) e no estado de eutiroidismo. RESULTADOS: O PC foi de 59,62 ± 11,5 kg no estado de hipertiroidismo e de 69,91 ± 14,4 kg no estado de eutiroidismo (p < 0,001). O IMC aumentou de 23,1 ± 3,8 kg/m² para 27 ± 4,7 kg/m² durante o tratamento (p < 0,0001). Antes da terapia, 66,6% tinham IMC < 25 kg/m² e 33,3%, IMC > 25 kg/m². No estado de eutiroidismo, 38% dos pacientes apresentavam IMC < 25 kg/m² e 62%, IMC > 25 kg/m² (p = 0,01). No estado de eutiroidismo, encontrou-se significativa diminuição nos valores de IL-6 e TNF-alfa, mas nenhuma correlação entre IL-6 e TNF-alfa com PC ou IMC. CONCLUSÃO: Um importante aumento no PC e IMC foi observado durante o tratamento do hipertiroidismo e alterações de IL-6 e TNF-alfa relacionam-se somente com o retorno ao eutiroidismo.

Do patients gain weight after thyroidectomy for thyroid cancer?

BACKGROUND

Patients who undergo thyroidectomy often complain of weight gain, which they frequently attribute to inadequate thyroid hormone replacement. To assess the weight changes associated with thyroid hormone replacement or suppressive therapy after thyroidectomy, we measured the weights of patients before and after thyroidectomy and compared them to the weights of euthyroid patients with thyroid nodules who were being followed for many years.

METHODS

The weights and heights of 67 women and 35 men who underwent total thyroidectomy for thyroid cancer were recorded before and for a mean of 8.3 years after thyroidectomy. All patients received either suppressive or replacement doses of levothyroxine. As a comparison group, 70 women and 22 men with goiter or thyroid nodules and were euthyroid had serial measurements of height and weight. They were followed for a mean of 7.6 years. The body mass index (BMI) and age-adjusted BMI percentiles were calculated. The weight, BMI, and BMI percentile changes were compared both unadjusted and adjusted for age, gender, thyrotropin (TSH) level, and duration between measurements.

RESULTS

At baseline, patients with thyroid nodules were older (mean 50.4 years) than those with thyroid cancer (mean 45.8 years). There were no significant differences in baseline weight, BMI, or BMI percentile. The baseline TSH levels were lower for patients with thyroid cancer (mean 0.8 mIU/L) than for those with nodules (mean 1.8 mIU/L) (p=0.002). There were no significant differences between the changes in weight, BMI, or BMI percentile from the start to the completion of the study whether unadjusted or after adjustment for age, gender, TSH, and duration of follow-up.

CONCLUSIONS

Despite the perception of many patients that their thyroidectomy and thyroid hormone replacement or suppressive therapy is responsible for their subsequent weight gain, there were no significant differences in weight gain over time in comparison to a control group of euthyroid patients with thyroid nodules or goiter.

Weight changes in euthyroid patients undergoing thyroidectomy

BACKGROUND

Thyroidectomized patients frequently report weight gain resistant to weight loss efforts, identifying their thyroidectomy as the event precipitating subsequent weight gain. We wished to determine whether recently thyroidectomized euthyroid patients gained more weight over 1 year than matched euthyroid patients with preexisting hypothyroidism.

METHODS

We performed a retrospective chart review of subjects receiving medical care at an academic medical center. One hundred twenty patients had their weight and thyroid status documented after thyroidectomy and achievement of euthyroidism on thyroid hormone replacement, and one year later. Three additional groups of 120 patients with preexisting hypothyroidism, no thyroid disease, and thyroid cancer were matched for age, gender, menopausal status, height, and weight. Anthropometric data were documented at two time points 1 year apart. We compared the weight changes and body mass index changes occurring over a 1-year period in the four groups.

RESULTS

Patients with recent postsurgical hypothyroidism gained 3.1 kg during the year, whereas matched patients with preexisting hypothyroidism gained 2.2 kg. The patients without thyroid disease and those with iatrogenic hyperthyroidism gained 1.3 and 1.2 kg, respectively. The weight gain in the thyroidectomized group was significantly greater than that in the matched hypothyroid group (p-value 0.004), the group without thyroid disease (p-value 0.001), and the patients with iatrogenic hyperthyroidism (p-value 0.001). Within the thyroidectomized group, the weight gain in menopausal women was greater than in either premenopausal women (4.4 vs. 2.3 kg, p-value 0.007) or men (4.4 vs. 2.5 kg, p-value 0.013).

CONCLUSION

Patients who had undergone thyroidectomy in the previous year did, in fact, gain more weight than their matched counterparts with preexisting hypothyroidism. In addition, all patients with hypothyroidism, even though treated to achieve euthyroidism, experienced more weight gain than both subjects without hypothyroidism and subjects with iatrogenic hyperthyroidism. The greatest weight gain in the thyroidectomized group was in menopausal women. These data raise the question of an unidentified factor related to taking thyroid hormone replacement that is associated with weight gain, with an additional intriguing effect of thyroidectomy itself. Menopausal status confers additional risk. These groups should be targeted for diligent weight loss efforts.

Treatment of pediatric Graves' disease is associated with excessive weight gain

CONTEXT

Little information is available about changes in body weight and body mass index in children before, during, and after treatment for Graves' disease (GD).

OBJECTIVE

Our objective was to examine changes in body weight after treatment for GD in children as related to clinical features.

DESIGN

The medical records of 43 pediatric patients with GD [35 girls and eight boys, aged 4.0-18.5 (mean 10.9) yr] were examined. Patients were included if clinical data were available for 1 yr before and after the diagnosis of GD.

MAIN OUTCOME MEASURES

Weight, height, body mass index (BMI) z-scores, and thyroid hormone levels were assessed.

RESULTS

Overall, patients presented with an average BMI z-score of -0.02 ± 1.05 that was not different from the normal population (P = 0.921) or their premorbid values (P = 0.07). However, in the subset of patients who were initially overweight or obese in the premorbid state, the BMI decreased significantly during the development of hyperthyroidism (P < 0.05). After initiation of treatment, patients gained significant amounts of weight over the first 6 months leading to elevated BMI z-scores (P < 0.0001), and elevations in BMI persisted in about 25% of the patients.

CONCLUSION

Excessive weight gain within 6 months of treatment is seen in children treated for GD, and the gain in weight can persist.

Why are our hypothyroid patients unhappy? Is tissue hypothyroidism the answer?

A large number of hypothyroid patients, receiving adequate doses of thyroxine supplementation, continue to complain of dissatisfaction and varied symptoms. This review discuses the concept of tissue hypothyroidism and suggests methods of measuring it, while calling for improvements in the medical management of hypothyroidism.

Serum TSH related to measures of body mass: longitudinal data from the HUNT Study, Norway

OBJECTIVE

Thyroid function and body mass are related, but the causal relationship remains unclear. Our objective was to investigate the longitudinal relationship between thyroid stimulating hormone (TSH) and body mass measures [body weight, body mass index (BMI), waist circumference (WC) and waist-hip-ratio (WHR)].

DESIGN

We used data from two waves of a population-based study: HUNT 2 (1995-1997) and 3 (2006-2008). Average follow-up time was 10·5 years. Multivariable general linear and logistic regression models were used to assess the relation between TSH and the body mass measures.

PARTICIPANTS

In total 9954 women and 5066 men without self-reported thyroid disease and TSH within the reference range (0·5-3·5 mU/l) at baseline and <10 mU/l at follow-up.

RESULTS

For each mU/l increase in TSH among women, weight increased 0·9 kg (95% CI 0·8, 1·1), BMI 0·3 kg/m(2) (95% CI 0·3, 0·4) and WC 0·6 cm (95% CI 0·3, 0·8). In men, the corresponding figures were 0·8 kg (95% CI 0·5, 1·0), 0·2 kg/m(2) (95% CI 0·2, 0·3) and 0·5 cm (95% CI 0·2, 0·8). In line with this, a weight gain of more than 5 kg was associated with a TSH increase of 0·08 mU/l (95% CI 0·06, 0·11) in women and 0·15 mU/l (95% CI 0·12, 0·18) in men. Women who lost more than 5 kg decreased their TSH by 0·12 mU/l (95% CI 0·09, 0·16) and men by 0·03 mU/l (95% CI -0.02, 0·09).

CONCLUSION

Weight gain is accompanied by increasing TSH, and weight loss in women is related to decreasing TSH.

Reverse causation and illness-related weight loss in observational studies of body weight and mortality

In studies of weight and mortality, the construct of reverse causation has come to be used to imply that the exposure-outcome relation is biased by weight loss due to preexisting illness. Observed weight-mortality associations are sometimes thought to result from this bias. Evidence for the occurrence of such bias is weak and inconsistent, suggesting that either the analytical methods used have been inadequate or else illness-related weight loss is not an important source of bias. Deleting participants has been the most frequent approach to control possible bias. As implemented, this can lead to deletion of almost 90% of all deaths in a sample and to deletion of more overweight and obese participants than participants with normal or below normal weight. Because it has not been demonstrated that the procedures used to adjust for reverse causation increase validity or have large or systematic effects on relative risks, it is premature to consider reverse causation as an important cause of bias. Further research would be useful to elucidate the potential effects and importance of reverse causation or illness-related weight loss as a source of bias in the observed associations between weight and mortality in cohort studies.

Energy Homeostasis and Body Weight before and after Cessation of Block and Replacement Therapy in Euthyroid Patients with Graves' Disease

Patients with Graves' hyperthyroidism (GH) treated with a combination of thyrostatic drugs and T(4), that is, block and replacement therapy (BRT), often report body weight (BW) gain. We aimed to determine changes in BW and energy metabolism upon cessation of BRT in these patients, and to identify possible endocrine determinants. We analysed 22 patients with GH (i) during BRT, and (ii) 12 weeks after BRT cessation. Patients were euthyroid at both visits. There were no differences in BW or resting energy expenditure (REE) between visits. At visit 1, after 13.5 (9.5-48.0) months of BRT, serum free (F)T(4) correlated positively with REE (r = 0.433, P = 0.044) and negatively with body fat % (r = -0.450, P = 0.035). Plasma FT(3) and FT(3)/FT(4) ratio showed an increase 12 w after cessation of BRT (20%, P < 0.0001 and 16%, P = 0.007, resp.). Moreover, the relative change in FT(3)/FT(4) ratio showed a significant, positive correlation with the relative change in REE between the 2 visits (r = 0.465, P = 0.029). In conclusion, serum FT(4) determines REE in euthyroid patients with GH treated with BRT. Twelve weeks after BRT cessation, BW and energy homeostasis are unaltered. However, as serum FT(3)/FT(4) ratio increases after cessation of BRT, which is a positive determinant of changes in REE, a longer term BW decrease is likely to occur.

Male sex, African American race or ethnicity, and triiodothyronine levels at diagnosis predict weight gain after antithyroid medication and radioiodine therapy for hyperthyroidism

OBJECTIVE

To determine whether racial or ethnic differences affect weight gain after treatment of hyperthyroidism and to reassess established risk factors such as sex, age, and cause of hyperthyroidism.

METHODS

We conducted a retrospective review of medical records of 111 patients treated with radioiodine (RAI) for hyperthyroidism, with or without preceding antithyroid medication, during 2002 to 2005. We ascertained age, sex, race or ethnicity, insurance status, compliance with visits, serum triiodothyronine (T3) level at diagnosis, and cause of hyperthyroidism. Weights and serum thyroidstimulating hormone levels were obtained at diagnosis, at time of RAI therapy, and at 0 to 4 months, 4 to 8 months, 8 to 12 months, and 24 months after RAI treatment.

RESULTS

There was a significant weight increase after treatment of hyperthyroidism. Levels of T3 at initial diagnosis of hyperthyroidism, male sex, and black or Hispanic ethnicity were found to be independent predictors of weight gain after RAI treatment. We found a significant interaction between race or ethnicity and sex in multivariate models. There was no difference in thyroid function across racial or ethnic groups or the sexes. Age, cause of hyperthyroidism, posttreatment thyroid-stimulating hormone level, compliance, and insurance status were not found to be significant predictors of weight gain.

CONCLUSION

The T3 level at the time of diagnosis of hyperthyroidism is a strong predictor of weight gain after treatment of hyperthyroidism. Black race or ethnicity and male sex are also risk factors for weight gain.

Treatment of paediatric hyperthyroidism but not hypothyroidism has a significant effect on weight

OBJECTIVE

Thyroid hormones are involved in metabolic regulation, but the degree to which they affect body weight and body mass index (BMI) in children is unclear. We examined the effect of hypo- and hyperthyroidism on weight and BMI at the time of diagnosis and after appropriate treatment.

DESIGN

Prospective and retrospective case series.

PATIENTS

Children referred for thyroid dysfunction were enrolled prospectively if their total or free T4 was elevated with TSH <0·05 mIU/ml (N = 57) or if they had a subnormal total or free T4 and TSH >20 (N = 29).

RESULTS

Almost all patients had at least 2 classic signs or symptoms including goitre, but hyperthyroid patients had more symptoms. Mean BMI z scores at the time of diagnosis did not significantly differ between the two groups. Males with hyperthyroidism complained of weight loss more frequently and had a lower pretreatment BMI z score than hyperthyroid females. Hypothyroid patients lost a minimal amount of weight by the first follow-up (mean of 0·3 kg) and on average gained weight by the second follow-up visit. In contrast hyperthyroid patients gained a mean of 3·4 kg at the first follow-up visit and a mean of 7·1 kg by the second.

CONCLUSIONS

Correction of hypothyroidism resulted in minimal weight loss, suggesting that hypothyroidism does not cause significant weight gain in children. In contrast, correction of the hyperthyroid state had a somewhat greater impact on weight status. These results are consistent with prior reports but surprising given the opposite metabolic effects of hypo- and hyperthyroidism.

Association of serum TSH with high body mass differs between smokers and never-smokers

CONTEXT

Recent studies have suggested that the association of low thyroid function with high body mass is restricted to nonsmokers.

OBJECTIVE

The aim was to study the association of thyroid function with body mass separately for smokers and never-smokers.

DESIGN AND SETTING

We conducted a cross-sectional, population-based study.

SUBJECTS

We studied 27,097 individuals older than 40 yr of age who were without previously known thyroid disease.

MAIN OUTCOME MEASURES

We measured mean body mass index (BMI) and odds ratio for obesity (BMI > or = 30.0 kg/m(2)) according to categories of thyroid function, in women and men, and separately for current smokers and never-smokers. We also studied the association with BMI within the reference range of TSH (0.50-3.5 mU/liter).

RESULTS

TSH within the reference range was positively associated with BMI (P for trend < or = 0.001 in all groups) and with the prevalence of obesity (P for trend < 0.005 in all groups). Among women, the association did not differ between current smokers and never-smokers, but in men the association was stronger for current smokers. Hypothyroid function was associated with higher BMI and higher prevalence of obesity in women (subclinical and overt hypothyroidism) and men (subclinical hypothyroidism), both in current smokers and in never-smokers.

CONCLUSION

The association of low thyroid function with high body mass was as least as strong in current smokers as in never-smokers, and our results clearly show that the association is not limited to nonsmokers, as previously suggested.

Prediction of cure and risk of hypothyroidism in patients receiving 131I for hyperthyroidism

CONTEXT

There is little consensus regarding the most appropriate dose of radioiodine ((131)I) to be administered to patients with hyperthyroidism.

OBJECTIVE

To compare the efficacy of fixed dose regimens of (131)I in curing hyperthyroidism and to define simple clinical and biochemical factors that predict outcome in individual patients.

DESIGN

Consecutive series of hyperthyroid subjects treated with (131)I.

SETTING

Single Secondary/Tertiary Care Hospital Clinic.

PARTICIPANTS

A total of 1278 patients (1013 females and 262 males, mean age 49.7 years) presenting with hyperthyroidism between 1984 and 2006.

INTERVENTION

Treatment with (131)I using a fixed dose regimen.

MAIN OUTCOME MEASURES

Probability of cure and risk of development of hypothyroidism following a single dose of (131)I.

RESULTS

Patients given a single dose of (131)I of 600 MBq (n = 485) had a higher cure rate (84.1%) compared with those receiving either 370 MBq (74.9%, P < 0.001) or those given 185 Bq (63%, P < 0.001). An increased incidence of hypothyroidism by 1 year was evident with higher doses (600 MBq: 60.4%; 370 MBq: 49.2%, P = 0.001; 185 Bq: 38.1%, P < 0.001). Binary logistic regression analysis identified a 600 Bq dose of (131)I [adjusted odds ratio, AOR 3.33 (2.28-4.85), P < 0.001], female gender [AOR 1.75 (1.23-2.47), P = 0.002], lower presenting serum free T4 concentration [AOR 1.01 (1.01-1.02), P < 0.001] and absence of a palpable goitre [AOR 3.33 (2.00-5.56), P < 0.001] to be independent predictors of cure. Similarly, a 600 MBq dose [AOR 3.79 (2.66-5.38), P < 0.001], female gender [AOR 1.46 (1.05-2.02), P = 0.02], younger age [AOR 1.03 (1.02-1.04), P < 0.001], absence of a palpable goitre [AOR 3.85 (2.38-5.88), P < 0.001] and presence of ophthalmopathy [AOR 1.57 (1.06-2.31), P = 0.02] were identified as independent factors predicting the probability of development of hypothyroidism at one year. Based on these findings, formulae to indicate probability of cure and risk of hypothyroidism for application to individual patients were derived.

CONCLUSIONS

Simple clinical/biochemical criteria can be used to predict outcome after (131)I treatment. These factors determine that males, those with severe biochemical hyperthyroidism, and those with a palpable goitre require larger doses (600 MBq) in order to achieve cure.

Weight gain during the treatment of thyrotoxicosis using conventional thyrostatic treatment

OBJECTIVE

Patients often lose considerable weight prior to the diagnosis of thyrotoxicosis. Regaining weight with treatment of thyrotoxicosis until hormone levels normalise is expected. This study was aimed to determine whether patients continued to put on weight once they were euthyroid.

STUDY DESIGN AND METHOD

The records of 60 consecutive euthyroid patients were studied. All patients were rendered euthyroid on thyrostatic medication alone. Patients on a block and replacement regime, those who developed transient hypothyroidism on treatment or other diagnoses causing weight gain were excluded.

RESULTS

The mean age of study group was 46.13 yr (21-73). Male:female ratio was 5:55. 36 (60%) patients had diagnosis of Graves' disease. On initial presentation weight was 67.75 kg (SEM 2.1) with body mass index (BMI) of 25.8. Patients took 6.7 months (mean) to become euthyroid. Mean weight when euthyroid was 71.61 kg (range 46-125). Even after becoming euthyroid, patient continued to gain weight at 3, 6, and 9 months and mean weight gain was 2.04 kg (SD 18.14) at 3 months (p=0.003). This weight gain was not related to patients' age, gender, BMI, duration or dose of treatment required to achieve euthyroidism. Diagnosis of Graves' disease and non-smoking status independently predicted weight gain.

CONCLUSION

We have demonstrated that patients with thyrotoxicosis continue to gain weight for at least 6 months even after becoming euthyroid. Patients with Graves' disease were more likely to gain weight compared to others. Smokers gained least weight. Preventing this weight gain warrants further investigation.

Hypothalamic thyroid hormone in energy balance regulation

Thyroid hormone has been known for decades as a hormone with profound effects on energy expenditure and ability to control weight. The regulation of energy expenditure by thyroid hormone primarily occurs via regulation of the activity, or expression, of uncoupling proteins in peripheral tissues. However, mechanistically this requires a signal from the brain to change circulating levels of thyroxine and thyroid hormone or increased sympathetic drive to peripheral tissues to alter local thyroid hormone levels via increased expression of type 2 deiodinase. However, little consideration has been given to the potential role and involvement of thyroid hormones action in the brain in the regulation of energy balance. Recent evidence implicates thyroid hormone as a shortterm signal of energy deficit imposed by starvation. Furthermore, thyroid hormone action within the hypothalamus is involved in adjusting long-term energy expenditure in seasonal animals which endure food shortages in winter. Evidence from several studies suggests that regulation of type 2 and type 3 deiodinase enzymes in tanycytes of the third ventricle are gatekeepers of thyroid hormone levels in the hypothalamus. This paper reviews some of the evidence for the role of deiodinase enzymes and the actions of thyroid hormone in the hypothalamus in the regulation of energy balance.

Subnormal energy expenditure: a putative causal factor in the weight gain induced by treatment of hyperthyroidism

AIMS

To examine the causes of weight gain occurring as an adverse effect of treatment of hyperthyroidism.

METHODS

We measured 24-h energy expenditure (EE), body composition and spontaneous physical activity (SPA) in eight patients before and 1 year after treatment of hyperthyroidism was initiated, and eight controls.

RESULTS

One year after initiation of treatment thyrotropin was normalized, thyroid hormones had fallen to the lower end of the reference range and fat mass had increased by 3.5 kg (p < 0.001). Twenty-four hour EE adjusted for fat-free mass (FFM) was 15% higher in hyperthyroid patients before treatment than in controls (p = 0.003), and treatment decreased 24-h EE by 1.9 MJ/day (p = 0.001). After treatment, 24-h EE, adjusted for FFM, was similar to the controls. Multiple regression analyses showed that the suppressed EE could partly be attributed to an iatrogenic suppression of thyroid hormones, resulting in lower sleeping EE. Twenty-four hour SPA was normal in the hyperthyroid state, but decreased after treatment by 21% (p = 0.045), to a level not significantly different, but still below that of the controls.

CONCLUSIONS

The study suggests that weight gain during treatment of hyperthyroidism might be due to subnormal levels of EE and SPA caused by a suppression of the thyroid hormone to a level in the lower end of the normal range.

Lack of association between serum TSH or free T4 and body mass index in euthyroid subjects

BACKGROUND

There is ongoing debate regarding the influence of minor changes in thyroid status within the normal range and body mass index (BMI). Overt thyroid dysfunction is well recognized to affect weight, but the influence of minor perturbations of thyroid function remains unclear.

AIM OF THE STUDY

To examine in euthyroid subjects the association of serum concentrations of TSH and free T4 within the normal range and BMI. To compare serum TSH and free T4 concentrations in nonobese and obese subjects.

SUBJECTS AND METHODS

A cohort of 401 euthyroid subjects with normal serum TSH (361 females, 40 males, mean age 48.2 years) who had been referred to a Thyroid Clinic due to the presence of a thyroid nodule or goitre. Measurements of serum TSH and free T4 were recorded, together with BMI (calculated from weight and height). Associations between measures of TSH, free T4 and BMI were investigated.

RESULTS

There was no association between either serum TSH or free T4 concentration when considered as a continuous variable and BMI, and no difference in BMI when subjects were categorized according to serum TSH or free T4. There was also no difference in serum TSH or free T4 between lean and obese euthyroid subjects. Evidence of thyroid autoimmunity indicated by the presence of antibodies to thyroid peroxidase was likewise not associated with a difference in BMI.

CONCLUSION

This study provides no evidence for an association between thyroid status within the normal range and BMI.

Quality of life with well-differentiated thyroid cancer: treatment toxicities and their reduction

INTRODUCTION

Patients with well-differentiated thyroid cancer have a good prognosis but a significant chance for local recurrence. In the past, limited surgery with postoperative 131I only for extremely high-risk cases or recurrence was not uncommon. As more aggressive surgical and postoperative treatments appear to gain wider acceptance, toxicity and long-term morbidity become more important issues. Our goal is to present the experience of a single institution with emphasis on oral side effects related to 131I as well as acute and chronic symptoms related to this diagnosis and their impact on quality of life.

METHODS

Fifty-seven patients were followed for a median time of 19.3 months. All patients received therapeutic 131I (mean dose, 154.7 mCi) between January 1, 1996 and August 30, 2002.

RESULTS

Fifty-four patients (94.7%) were alive at the time of analysis. Sixteen (28.1%) required a second treatment: any sign of persistence resulted in retreatment. Complaints with 131I treatment included altered taste, 26.3%; acute xerostomia, 21.1%; and acute sialoadenitis, 15.8%. Chronic xerostomia occurred in 6 (35.3%) of all patients who received multiple treatments. The incidence of chronic xerostomia was reduced to 1 of 11 (9.1%) with amifostine pretreatment. Other chronic side effects associated with this disease included fatigue 54.4%, weight gain of more than 6 months duration 24.6%, with 12 (27.9%) of those under 60 experiencing an average gain of 2.3 kg from initial diagnosis.

CONCLUSION

Review of treatment-related symptoms prompted policies to reduce toxicity including amifostine pretreatment for 131I therapy and thyrotropin (synthetic TSH) use in place of iatrogenic hypothyroidism for thyroglobulin testing and scanning.

Fatigue, Weight Gain, Lethargy and Amenorrhea in Breast Cancer Patients on Chemotherapy: Is Subclinical Hypothyroidism the Culprit?

BACKGROUND

The purpose of this study was to prospectively observe the relative contribution of each viable mechanism such as hyperphagia, physical activity, body composition, steroid hormonal and thyroid function, fatigue scores on changes in body weight in breast cancer patients, receiving adjuvant chemotherapy.

METHODS

This was a prospective observational research design where 198 consecutive breast cancer patients receiving adjuvant chemotherapy were monitored from start to end and 6 months post-therapy on changes in anthropometics, fatigue, nutritional intake, physical activity, thyroid and steroid hormones.

RESULTS

We observed a weight gain over >5 lb in 22.2% of this patient population with a significant and progressive gain of 6.7 lb (P < 0.0001) at 6 months. Ninety four percent of all patients reported fatigue and 56% of patients reported lowered physical activity. A significant reduction in serum free and total estradiol (P < 0.0001) was observed indicative of reduction in ovarian function with 86% amenorrehic at the end of treatment. A significant reduction in mean serum triiodothyronine uptake levels (P < 0.05), in addition to a significant increase in TBG (P < 0.0001) from baseline to end of chemotherapy, was observed. In addition 20-25% of this patient group was already diagnosed with clinical hypothyroidism at diagnosis and treated. Changes in fatigue frequency and serum sex-hormone-binding globulin (SHBG) were variables significantly predictive of weight gain (P < 0.0001).

CONCLUSIONS

Cytotoxic agents may influence thyroid function in breast cancer patients contributing to and progressively worsening symptoms such as weight gain, amenorrhea, fatigue and lowered physical activity in this population. The present study indicates the value of screening breast cancer patients for thyroid function at diagnosis or pre-treatment.

Crohn’s disease and risk of fracture: does thyroid disease play a role?

AIM: To assess the role of thyroid disease as a risk for fractures in Crohn’s patients.

METHODS: A cross-sectional study was conducted from 1998 to 2000. The study group consisted of 210 patients with Crohn’s disease. A group of 206 patients without inflammatory bowel disease served as controls. Primary outcome was thyroid disorder. Secondary outcomes included use of steroids, immunosuppressive medications, surgery and incidence of fracture.

RESULTS: The prevalence of hyperthyroidism was similar in both groups. However, the prevalence of hypothyroidism was lower in Crohn’s patients (3.8% vs 8.2%, P = 0.05). Within the Crohn’s group, the use of immunosuppressive agents (0% vs 11%), steroid usage (12.5% vs 37%), small bowel surgery (12.5% vs 28%) and large bowel surgery (12.5% vs 27%) were lower in the hypothyroid subset as compared to the euthyroid subset. Seven (3.4%) Crohn’s patients suffered fracture, all of whom were euthyroid.

CONCLUSION: Thyroid disorder was not found to be associated with Crohn’s disease and was not found to increase the risk for fractures. Therefore, screening for thyroid disease is not a necessary component in the management of Crohn’s disease.

Psychological well-being in patients on 'adequate' doses of l-thyroxine: results of a large, controlled community-based questionnaire study

OBJECTIVE

Over 1% of the UK population is receiving thyroid hormone replacement with l-thyroxine (T4). However, many patients complain of persistent lethargy and related symptoms on T4 even with normal TSH levels. To date there has been no large study to determine whether this is related to thyroxine replacement or coincidental psychological morbidity. We have therefore attempted to address this issue using a large, community-based study.

DESIGN AND PATIENTS

Computerized prescribing records of five general practices were used to identify 961 patients who had been on thyroxine for a minimum of 4 months from a population of 63 000 (1.5%), along with age- and sex-matched controls. All 1922 individuals were sent a two-page questionnaire, made up of the short form of the General Health Questionnaire (GHQ-12), designed to detect minor psychiatric disorders in the community, and a 12-question 'thyroid symptom questionnaire' (TSQ) in the same format. A covering letter explained that we were interested in 'how patients felt on medication' and made no direct reference to thyroxine.

MEASUREMENTS

Scores from the GHQ and TSQ were marked for each individual using the GHQ and Likert scoring methods. Patients' latest TSH measurements were obtained from laboratory records. Comparisons were then made on scores for the total GHQ-12, TSQ and individual questions between patients (P) and control (C) groups. Separate analyses were made comparing the patients with a normal TSH (nP) and the control group.

RESULTS

Five hundred and ninety-seven (62%) of the patients (P) and 551 (57%) of the controls (C) responded and fully completed at least one of the two questionnaire. Three hundred and ninety-seven responding patients (nP) had a TSH estimation performed in the previous 12 months with the last result being in the local laboratory normal range for TSH (0.1-5.5 or 0.2-6.0 mU/l, according to the assay method used). The responding P, nP and C populations were well matched for age (59.96, 59.73, 59.35 years) and sex (85%, 83%, 87% female). The number of individuals scoring 3 or more on the GHQ-12 (indicating 'caseness') was 21% higher in P than C [185/572 (32.3%) vs. 137/535 (25.6%), P = 0.014] and 26% higher in nP than C [131/381 (34.4%) vs. 137/535 (25.6%), P < 0.005]. Stronger differences were seen with the TSQ scores [C = 187/535 (35.0%), P = 273/583 (46.8%), P < 0.001, P vs. C; and nP = 189/381 (48.6%), P < 0.001, nP vs. C]. Differences existed in chronic drug use and chronic disease prevalence between the control and patient groups, but the differences in GHQ and TSQ scores between the groups remained significant even after correction for these factors as well as age and sex in multiple regression analysis.

CONCLUSIONS

This community-based study is the first evidence to indicate that patients on thyroxine replacement even with a normal TSH display significant impairment in psychological well-being compared to controls of similar age and sex. In view of the large numbers of people on thyroxine replacement, we believe that these differences, although not large, could contribute to significant psychological morbidity in a substantial number of individuals.