Synchronicity of frequently sampled thyrotropin (TSH) and leptin concentrations in healthy adults and leptin-deficient subjects: evidence for possible partial TSH regulation by leptin in humans

Metabolic Messengers: Thyroid Hormones

Thyroid hormones (THs) are key hormones that regulate development and metabolism in mammals. In man, the major target tissues for TH action are the brain, liver, muscle, heart, and adipose tissue. Defects in TH synthesis, transport, metabolism, and nuclear action have been associated with genetic and endocrine diseases in man. Over the past few years, there has been renewed interest in TH action and the therapeutic potential of THs and thyromimetics to treat several metabolic disorders such as hypercholesterolemia, dyslipidaemia, non-alcoholic fatty liver disease (NAFLD), and TH transporter defects. Recent advances in the development of tissue and TH receptor isoform-targeted thyromimetics have kindled new hope for translating our fundamental understanding of TH action into an effective therapy. This review provides a concise overview of the historical development of our understanding of TH action, its physiological and pathophysiological effects on metabolism, and future therapeutic applications to treat metabolic dysfunction.

Total weight loss induces the alteration in thyroid function after bariatric surgery

Background

Bariatric surgery is an effective approach to weight loss, which may also affect thyroid function. However, alteration in thyroid-stimulating hormone (ΔTSH) and thyroid hormones after bariatric surgery and the relationship between thyroid function and postoperative weight loss still remains controversial.

Methods

Data were collected from euthyroid patients with obesity who underwent sleeve gastrectomy and Roux-en-Y gastric bypass from 2017 to 2022. The alterations of free thyroxine (FT4), free triiodothyronine (FT3), total thyroxine (TT4), total triiodothyronine (TT3), and TSH were calculated 1 year after surgery. Pearson correlation analysis was used to assess the correlation between the percentage of total weight loss (%TWL) and ΔTSH. Multivariable linear regression was utilized to determine the association between %TWL and ΔTSH.

Results

A total of 256 patients were included in our study. The mean %TWL was 28.29% after 1 year. TSH decreased from 2.33 (1.67, 3.04) uIU/mL to 1.82 (1.21, 2.50) uIU/mL (P < 0.001), FT3 decreased from 3.23 ± 0.42 pg/mL to 2.89 ± 0.41 pg/mL (P < 0.001), FT4 decreased from 1.11 ± 0.25 ng/dL to 1.02 ± 0.25 ng/dL (P < 0.001), TT3 decreased from 1.13 (1.00, 1.25) ng/mL to 0.89 (0.78, 1.00) ng/mL (P < 0.001), and TT4 decreased from 8.28 ± 1.69 ug/mL to 7.82 ± 1.68 ug/mL 1 year postoperatively (P < 0.001). %TWL was found to be significantly correlated to ΔTSH by Pearson correlation analysis (Pearson correlation coefficient = 0.184, P = 0.003), indicating that the more weight loss, the more TSH declined. After adjusting for covariates in multivariable linear regression, %TWL was found to be independently associated with ΔTSH (β = 0.180 [95% confidence interval (CI), 0.048 - 0.312], P = 0.008). Moreover, %TWL was divided into 3 categorical groups (%TWL ≤ 25%, 25% < %TWL ≤ 35%, and %TWL > 35%) for further exploration, and was also found to be an independent predictor for ΔTSH after adjusting for covariates in multivariable linear regression (β = 0.153 [95% CI, 0.019 - 0.287], P = 0.025).

Conclusion

TSH, FT4, FT3, TT4, and TT3 decrease significantly 1 year after bariatric surgery. The decline in TSH is independently mediated by postoperative weight loss; the more the weight loss, the more the TSH decrease.

Management of Monogenic and Syndromic Obesity

Similar to the general population, lifestyle interventions focused on nutrition and physical activity form the foundation for treating obesity caused by rare genetic disorders. Additional therapies, including metreleptin and setmelanotide, that target defects within the leptin signaling pathway can effectively synergize with lifestyle efforts to treat monogenic disorders of leptin, leptin receptor, proopiomelanocortin (POMC), and proprotein convertase subtilisin/kexin type 1 (PCSK1) and syndromic conditions, such as the ciliopathies Bardet-Biedl and Alström syndromes, whose pathophysiological mechanisms also converge on the leptin pathway. Investigational treatments for Prader-Willi syndrome target specific defects caused by reduced expression of paternally derived genes within the chromosome 15q region.

Direct androgen receptor control of sexually dimorphic gene expression in the mammalian kidney

Mammalian organs exhibit distinct physiology, disease susceptibility, and injury responses between the sexes. In the mouse kidney, sexually dimorphic gene activity maps predominantly to proximal tubule (PT) segments. Bulk RNA sequencing (RNA-seq) data demonstrated that sex differences were established from 4 and 8 weeks after birth under gonadal control. Hormone injection studies and genetic removal of androgen and estrogen receptors demonstrated androgen receptor (AR)-mediated regulation of gene activity in PT cells as the regulatory mechanism. Interestingly, caloric restriction feminizes the male kidney. Single-nuclear multiomic analysis identified putative cis-regulatory regions and cooperating factors mediating PT responses to AR activity in the mouse kidney. In the human kidney, a limited set of genes showed conserved sex-linked regulation, whereas analysis of the mouse liver underscored organ-specific differences in the regulation of sexually dimorphic gene expression. These findings raise interesting questions on the evolution, physiological significance, disease, and metabolic linkage of sexually dimorphic gene activity.

Are physiological oscillations physiological?

Despite widespread and striking examples of physiological oscillations, their functional role is often unclear. Even glycolysis, the paradigm example of oscillatory biochemistry, has seen questions about its oscillatory function. Here, we take a systems approach to argue that oscillations play critical physiological roles, such as enabling systems to avoid desensitization, to avoid chronically high and therefore toxic levels of chemicals, and to become more resistant to noise. Oscillation also enables complex physiological systems to reconcile incompatible conditions such as oxidation and reduction, by cycling between them, and to synchronize the oscillations of many small units into one large effect. In pancreatic β-cells, glycolytic oscillations synchronize with calcium and mitochondrial oscillations to drive pulsatile insulin release, critical for liver regulation of glucose. In addition, oscillation can keep biological time, essential for embryonic development in promoting cell diversity and pattern formation. The functional importance of oscillatory processes requires a re-thinking of the traditional doctrine of homeostasis, holding that physiological quantities are maintained at constant equilibrium values, a view that has largely failed in the clinic. A more dynamic approach will initiate a paradigm shift in our view of health and disease. A deeper look into the mechanisms that create, sustain and abolish oscillatory processes requires the language of nonlinear dynamics, well beyond the linearization techniques of equilibrium control theory. Nonlinear dynamics enables us to identify oscillatory ('pacemaking') mechanisms at the cellular, tissue and system levels.

A National Multicenter Study of Leptin and Leptin Receptor Deficiency and Systematic Review

CONTEXT

Homozygous leptin (LEP) and leptin receptor (LEPR) variants lead to childhood-onset obesity.

OBJECTIVE

To present new cases with LEP and LEPR deficiency, report the long-term follow-up of previously described patients, and to define, based on all reported cases in literature, genotype-phenotype relationships.

METHODS

Our cohort included 18 patients (LEP = 11, LEPR = 7), 8 of whom had been previously reported. A systematic literature review was conducted in July 2022. Forty-two of 47 studies on LEP/LEPR were selected.

RESULTS

Of 10 new cases, 2 novel pathogenic variants were identified in LEP (c.16delC) and LEPR (c.40 + 5G > C). Eleven patients with LEP deficiency received metreleptin, 4 of whom had been treated for over 20 years. One patient developed loss of efficacy associated with neutralizing antibody development. Of 152 patients, including 134 cases from the literature review in addition to our cases, frameshift variants were the most common (48%) in LEP and missense variants (35%) in LEPR. Patients with LEP deficiency were diagnosed at a younger age [3 (9) vs 7 (13) years, P = .02] and had a higher median body mass index (BMI) SD score [3.1 (2) vs 2.8 (1) kg/m2, P = 0.02], which was more closely associated with frameshift variants (P = .02). Patients with LEP deficiency were more likely to have hyperinsulinemia (P = .02).

CONCLUSION

Frameshift variants were more common in patients with LEP deficiency whereas missense variants were more common in LEPR deficiency. Patients with LEP deficiency were identified at younger ages, had higher BMI SD scores, and had higher rates of hyperinsulinemia than patients with LEPR deficiency. Eleven patients benefitted from long-term metreleptin, with 1 losing efficacy due to neutralizing antibodies.

The Thyroid Hormone Axis and Female Reproduction

Thyroid function affects multiple sites of the female hypothalamic-pituitary gonadal (HPG) axis. Disruption of thyroid function has been linked to reproductive dysfunction in women and is associated with menstrual irregularity, infertility, poor pregnancy outcomes, and gynecological conditions such as premature ovarian insufficiency and polycystic ovarian syndrome. Thus, the complex molecular interplay between hormones involved in thyroid and reproductive functions is further compounded by the association of certain common autoimmune states with disorders of the thyroid and the HPG axes. Furthermore, in prepartum and intrapartum states, even relatively minor disruptions have been shown to adversely impact maternal and fetal outcomes, with some differences of opinion in the management of these conditions. In this review, we provide readers with a foundational understanding of the physiology and pathophysiology of thyroid hormone interactions with the female HPG axis. We also share clinical insights into the management of thyroid dysfunction in reproductive-aged women.

Thyroid Volume and Thyroid Function Parameters Are Independently Associated with Weight Status in Overweight Children

BACKGROUND

A relation between thyroid-stimulating hormone (TSH), insulin resistance - both of which are related to obesity - and thyroid volume has been suggested. Therefore, we analyzed thyroid volume and structure in relation to thyroid function parameters, weight status, and insulin resistance.

METHODS

This is a cross-sectional study in which weight status (BMI-SDS), thyroid function parameters (TSH, free tri-iodothyronine [fT3], and free thyroxine [fT4]), insulin resistance index (HOMA-IR), and thyroid volume (ultrasound) were determined in 617 overweight children (aged 10.4 ± 2.2 years, 50% male, BMI-SDS 2.5 ± 0.6) and in 27 normal-weight children of a similar age and gender. Furthermore, changes in thyroid volume and structure, and thyroid function parameters were analyzed in 83 obese children (51% male, mean age 10.3 ± 2.2) at baseline and at the end of a 1-year lifestyle intervention.

RESULTS

Overweight children had a significant greater thyroid volume (4.2 ± 1.8 vs. 4.1 ± 0.5 mL) and higher TSH (3.1 ± 1.5 vs. 2.4 ± 1.1 mU/L) and fT3 (4.4 ± 0.7 vs. 4.1 ± 0.5 pg/mL) concentrations compared to normal-weight children. In multiple linear regression analyses adjusted to multiple confounders, thyroid volume was significantly related to BMI-SDS (b coefficient 0.44 ± 0.10, r2 = 0.41) but not to any thyroid function parameter or HOMA-IR. Changes in BMI-SDS were significantly associated with changes in thyroid volume (r = 0.22). The changes in thyroid volume were not correlated to changes of any thyroid function parameter or HOMA-IR.

CONCLUSIONS

Thyroid volume is positively correlated to weight status in childhood obesity and the change is reversible after weight loss independently of thyroid function parameters and insulin resistance. Further studies are needed to understand why thyroid volume is increased reversibly in overweight children.

A fresh look to the phenotype in mono-allelic likely pathogenic variants of the leptin and the leptin receptor gene

Leptin (LEP) and leptin receptor (LEPR) play a major role in energy homeostasis, metabolism, and reproductive function. While effects of biallelic likely pathogenic variants (-/-) on the phenotype are well characterized, effects of mono-allelic likely pathogenic variants (wt/-) in the LEP and LEPR gene on the phenotype compared to wild-type homozygosity (wt/wt) have not been systematically investigated. We identified in our systematic review 44 animal studies (15 on Lep, 29 on Lepr) and 39 studies in humans reporting on 130 mono-allelic likely pathogenic variant carriers with 20 distinct LEP variants and 108 heterozygous mono-allelic likely pathogenic variant carriers with 35 distinct LEPR variants. We found indications for a higher weight status in carriers of mono-allelic likely pathogenic variant in the leptin and in the leptin receptor gene compared to wt/wt, in both animal and human studies. In addition, animal studies showed higher body fat percentage in Lep and Lepr wt/- vs wt/wt. Animal studies provided indications for lower leptin levels in Lep wt/- vs. wt/wt and indications for higher leptin levels in Lepr wt/- vs wt/wt. Data on leptin levels in human studies was limited. Evidence for an impaired metabolism in mono-allelic likely pathogenic variants of the leptin and in leptin receptor gene was not conclusive (animal and human studies). Mono-allelic likely pathogenic variants in the leptin and in leptin receptor gene have phenotypic effects disposing to increased body weight and fat accumulation.

A study of thyroid profile in patients suffering from the first episode of mania: A cross-sectional study

BACKGROUND

Thyroid function is commonly considered in the assessment of mood disorders. Reports of thyroid dysregulation in patients with mania are associated with several confounding factors. To eliminate confounding factors, studies of first-episode mania are desirable. This study tried to find out any relationship between thyroid disorders and mania.

AIM

The aim of this study is to assess and compare the thyroid profile between first-episode mania and healthy controls and to ascertain the correlation between severity and duration of the manic episode with FT3, FT4, and thyroid-stimulating hormone (TSH) levels.

MATERIALS AND METHODS

This was a cross-sectional study conducted in the psychiatry department of a tertiary care hospital. Forty consecutive drug-naïve patients with first-episode mania, diagnosed according to the International Classification of Disease-10 (study group), were matched with 40 healthy controls (control group). Both the groups were compared on the basis of thyroid profile and thyroid levels were correlated with duration and severity of illness in the study group.

RESULTS

Nearly 7.5% of cases in the study group had hyperthyroidism, whereas 5% had subclinical hyperthyroidism. In contrast, normal controls showed 5% and 10% prevalence of hypothyroidism and subclinical hypothyroidism, respectively. A statistically significant lower level of TSH was observed in the study group (P < 0.001), whereas the mean serum levels of FT3 and FT4 were higher in the study group, but the difference was statistically nonsignificant. No significant correlation of thyroid hormones level with duration and severity of illness was noted.

CONCLUSION

Our findings highlight a higher prevalence of hyperthyroidism in patients with mania and suggest the role of thyroid hormones in mania.

Effect of Thyroid Hormones on Adipose Tissue Flexibility

The recruitment and activation of energy-consuming brown adipocytes is currently considered as potential therapeutic approach to combat obesity. Thyroid hormones (TH) significantly contribute to full thermogenic capacity of brown adipocytes. A number of recent studies suggest that TH also induce the recruitment of brown adipocytes in white adipose depots, a process known as browning. In this review, we will summarize underlying mechanisms by which TH mediate brown adipose tissue activity and white adipose tissue browning. Furthermore, we will discuss the relevance of TH-induced white adipose tissue browning for thermoregulation.

Metabolic Diseases and Down Syndrome: How Are They Linked Together?

Down syndrome is a genetic disorder caused by the presence of a third copy of chromosome 21, associated with intellectual disabilities. Down syndrome is associated with anomalies of both the nervous and endocrine systems. Over the past decades, dramatic advances in Down syndrome research and treatment have helped to extend the life expectancy of these patients. Improved life expectancy is obviously a positive outcome, but it is accompanied with the need to address previously overlooked complications and comorbidities of Down syndrome, including obesity and diabetes, in order to improve the quality of life of Down syndrome patients. In this focused review, we describe the associations between Down syndrome and comorbidities, obesity and diabetes, and we discuss the understanding of proposed mechanisms for the association of Down syndrome with metabolic disorders. Drawing molecular mechanisms through which Type 1 diabetes and Type 2 diabetes could be linked to Down syndrome could allow identification of novel drug targets and provide therapeutic solutions to limit the development of metabolic and cognitive disorders.

Thyroid Hormone Changes After Sleeve Gastrectomy With and Without Antral Preservation

BACKGROUND

The effect of bariatric surgery on thyroid hormone changes yielded inconsistent results. The aim of the present study was to assess the change of thyroid hormone levels following laparoscopic sleeve gastrectomy (LSG), with or without antral preservation (AP).

METHODS

Thyroid hormones (TSH, FT3, FT4) were examined preoperatively, at the end of the first postoperative month, and first postoperative year. Secondly, antral resection (AR) and AP were compared at inducing weight loss and thereby affecting thyroid hormone levels.

RESULTS

Euthyroid obese patients (86 female/20 male) underwent LSG. Of these, 58 patients underwent AR and 48 patients AP. The mean FT3 levels significantly decreased both in the first postoperative month and the first year (P < 0.001), whereas mean TSH levels decreased significantly in the first postoperative year (P < 0.001). FT4 levels remained nearly unchanged (P = 0.517). Postoperative first year body mass index (BMI) loss, excess BMI loss percentile (%EBMIL), and total body weight loss percentile (%TWL) were significantly higher in AR group than the AP group (P ≤ 0.01). When the change in thyroid hormone levels was analyzed by pyloric distance according to time periods, no significant difference was found in TSH and FT4 levels (P > 0.05); however, reduction in FT3 levels was significantly greater in patients with AR than in AP patients (P = 0.028).

CONCLUSION

LSG promotes significant reduction in TSH and FT3 levels, whereas FT4 levels remain unchanged. LSG with AR provides more weight loss in short term and appears to be more effective at lowering FT3 levels.

Leptin and its actions on reproduction in males

Leptin, an adipocyte-derived hormone, serves numerous physiological functions in the body, particularly during puberty and reproduction. The exact mechanism by which leptin activates the gonadotropin-releasing hormone (GnRH) neurons to trigger puberty and reproduction remains unclear. Given the widespread distribution of leptin receptors in the body, both central and peripheral mechanisms involving the hypothalamic-pituitary-gonadal axis have been hypothesized. Leptin is necessary for normal reproductive function, but when present in excess, it can have detrimental effects on the male reproductive system. Human and animal studies point to leptin as a link between infertility and obesity, a suggestion that is corroborated by findings of low sperm count, increased sperm abnormalities, oxidative stress, and increased leptin levels in obese men. In addition, daily leptin administration to normal-weight rats has been shown to result in similar abnormalities in sperm parameters. The major pathways causing these abnormalities remain unidentified; however, these adverse effects have been attributed to leptin-induced increased oxidative stress because they are prevented by concurrently administering melatonin. Studies on leptin and its impact on sperm function are highly relevant in understanding and managing male infertility, particularly in overweight and obese men.

Laparoscopic Sleeve Gastrectomy-Induced Decreases in FT3 and TSH are Related to Fasting C-Peptide in Euthyroid Patients with Obesity

OBJECTIVE

Laparoscopic sleeve gastrectomy (LSG) is one of the most effective therapies to treat obesity. However, whether LSG affects thyroid function remains elusive. Due to a lack of longitudinal research, we explored changes in thyroid function in euthyroid patients with obesity before and after LSG.

METHODS

In total, 109 participants (59 obese patients, 30 normal controls and 20 overweight subjects) were recruited from the Second Xiangya Hospital of Central South University (CSU). All patients underwent LSG, and metabolic indicators and free triiodothyronine (FT3), free thyroxine (FT4), and thyroid stimulating hormone (TSH) were evaluated at baseline, 6 and 12 months postoperatively.

RESULTS

Compared to the normal control group, the concentrations of FT4 were decreased and TSH were increased in the obese group at baseline. Thyroid hormone levels in all participants were within the normal range during the 12 months after LSG. The concentrations of FT3 (4.83 ± 0.06 vs 5.03 ± 0.08, P = 0.023) and TSH (1.67 ± 0.11 vs 2.25 ± 0.18, P = 0.000) significantly decreased from baseline to 12 months postoperatively, while the concentrations of FT4 significantly increased (17.40 ± 0.52 vs 15.80 ± 0.32, P = 0.004). The decrease in fasting C-peptide (FCP) was related to the decline in FT3 and TSH during 12 months after LSG.

CONCLUSION

Obesity is closely related to thyroid function. LSG promoted a significant decrease in FT3 and TSH and a significant increase in FT4 in euthyroid patients with obesity after LSG. The decline in FCP may be involved in the decrease in FT3 and TSH after LSG.

The Association of Obesity with Autoimmune Thyroiditis and Thyroid Function-Possible Mechanisms of Bilateral Interaction

A growing number of patients suffer from autoimmune diseases, including autoimmune thyroid disease. There has simultaneously been a significant increase in the prevalence of obesity worldwide. It is still an open question whether adiposity can directly influence activation of inflammatory processes affecting the thyroid in genetically predisposed individuals. Adipokines, biologically active substances derived from the adipocytes, belong to a heterogenic group of compounds involved in numerous physiological functions, including the maintenance of metabolism, hormonal balance, and immune response. Notably, the presence of obesity worsens the course of selected autoimmune diseases and impairs response to treatment. Moreover, the excess of body fat may result in the progression of autoimmune diseases. Nutritional status, body weight, and energy expenditure may influence thyroid hormone secretion. Interestingly, thyroid hormones might influence the activity of adipose tissue as metabolic alterations related to fat tissue are observed under pathological conditions in which there are deficits or overproduction of thyroid hormones. Functioning TSH receptors are expressed on adipocytes. Thermogenesis may presumably be stimulated by TSH binding to its receptor on brown adipocytes. There could be a bilateral interaction between the thyroid and adipose. Obesity may influence the onset and course of autoimmune disease.

Thyroid Stimulating Hormone (TSH) Is Associated With General and Abdominal Obesity: A Cohort Study in School-Aged Girls During Puberty in East China

Objectives: Although the association between thyroid stimulating hormone (TSH) and obesity in children has been investigated in several cross-sectional studies, no study evaluated this association among girls during puberty, which were in a key period closely related to the fluctuations of thyroid hormones and development of obesity. Therefore, we conducted a cohort study to investigate the association of general and abdominal obesity with TSH in girls during puberty. Setting and participants: A cohort study of 481 school-aged girls during puberty was conducted in four regions in east China, with a baseline survey in 2017 and a follow-up survey in 2019. Outcome measures: Anthropometric indexes including height, weight and waist circumference (WC) were measured, and body mass index (BMI) was then calculated. Blood samples were collected to determine TSH and free thyroxine (FT4). Results: Of the 474 girls at baseline survey, the prevalences of BMI-based general obesity and WC-based abdominal obesity were 19.8% (94/474) and 21.7% (103/474), respectively. Compared with normal weight girls, the median serum TSH level was significantly higher in general obese girls (P = 0.037), but not in central obese girls (P = 0.173). Multiple logistic regression models indicated that those in the highest tertile of serum TSH level had a significantly higher risk of BMI-based overweight/obesity (OR = 1.83, 95% CI 1.01 to 3.32) compared with the lowest tertile. Analyses from 435 girls prospectively followed-up for 2 years revealed that those with general or central obesity also had higher follow-up TSH level (P = 0.004 and P = 0.008, respectively). The TSH level for girls with general obesity at baseline but normal weight at follow-up was 0.45 mU/L (95% CI 0.11 to 0.79) higher than those with normal weight at baseline and follow-up. Conclusions: TSH was positively associated with both general and abdominal obesity among girls during puberty.

Obese Subjects with Non-Alcoholic Fatty Liver Disease Have a Higher Risk of Thyroid Dysfunction

Objectives The effects of obesity on thyroid function have not been well established. The aim of this study was to investigate the effects of body mass index (BMI) and/or non-alcoholic fatty liver disease (NAFLD) on thyroid function. Methods A retrospective longitudinal analysis was conducted among subjects who underwent comprehensive health check-ups at least four times between 2008 and 2017. Thyroid function was investigated according to BMI or presence of NAFLD at the end of follow-up. The subjects were divided into four groups: control (n = 216), subjects with obese (n = 94), subjects with NAFLD (n = 48), and subjects with obese + NAFLD (n = 93). Obesity was defined as BMI ≥ 25 kg/m2. Results During the mean follow-up of 6.8 years (6.8 ± 1.2 years), 42 of the 451 subjects (9.3%) had subclinical hypothyroidism (SCH) but no subjects developed overt hypothyroidism. In multivariate Cox proportional hazard analysis, after adjustment for age, sex, smoking, and baseline thyroid stimulating hormone level, obese subjects with NAFLD had a higher risk of SCH than the control group. Conclusions The obese subjects with NAFLD had a higher risk for SCH in the future.

Associations between thyroid-stimulating hormone, blood pressure and adiponectin are attenuated in children and adolescents with overweight or obesity

Background The association between thyroid-stimulating hormone (TSH) concentrations and blood pressure is well described in adults, but only studied to a limited extent in children and adolescents and almost entirely in population-based cohorts. The present study investigates the association between TSH and blood pressure, and the influence of leptin and adiponectin, in a cohort of children and adolescents enrolled in obesity treatment compared with a population-based cohort. Methods We studied 4154 children and adolescents aged 6-18 years from an obesity clinic cohort and a population-based cohort from The Danish Childhood Obesity Data- and Biobank. Anthropometrics, blood pressure and biochemical markers, including TSH, leptin and adiponectin concentrations, were collected. Adjusted correlation and interaction analyses were performed. Results Patients from the obesity clinic cohort exhibited higher concentrations of TSH and higher blood pressure than participants from the population-based cohort. TSH standard deviation scores (SDS) were significantly associated with all blood pressure-related variables in the population-based cohort, but only with systolic blood pressure SDS and hypertension in the obesity clinic cohort. The interaction between TSH SDS and adiponectin was found to be independently associated with systolic blood pressure and hypertension in the population-based cohort only. Conclusions The significant associations between TSH, adiponectin and blood pressure, observed in children and adolescents from a population-based cohort, are attenuated or absent in children and adolescents with overweight or obesity, suggesting that childhood obesity distorts the healthy interplay between the thyroid axis, thyroid-adipokine interaction and blood pressure.

Thyroid function before and after Roux-en-Y gastric bypass: an observational study

BACKGROUND

Population studies have shown a positive association between thyroid-stimulating hormone (TSH) and body mass index. Recent studies have shown a significant increase in the prevalence of subclinical hypothyroidism (SCH) in obesity. Weight reduction after Roux-en-Y gastric bypass (RYGB) seems to significantly decrease TSH levels.

OBJECTIVES

The purpose of this study was to evaluate the prevalence of SCH in obese patients (class II and III) and to observe the behavior of thyroid hormones (TSH, hormone triiodothyronine, thyroxine, free thyroxine) with significant weight loss after RYGB.

SETTING

Hospital Nossa Senhora das Graças, Curitiba, Paraná, Brazil.

METHODS

We retrospectively reviewed the medical records of 215 obese patients who underwent RYGB between 2005 and 2012 with a follow-up of at least 2 years. The study was observational and descriptive. The selected times for clinical and laboratory evaluations were preoperative, 3, 6, 12, and 24 months after the procedure. Association, correlation, and variance analyses were performed.

RESULTS

The prevalence of SCH preoperatively was 9.3%. SCH was corrected in 89.5% of patients 12 months after RYGB. We did not find an association between TSH and BMI (r = .002, P = .971). There was a positive impact of bariatric surgery on all metabolic variables. We showed that serum TSH level had no positive correlation with the presence or absence of metabolic syndrome.

CONCLUSIONS

Weight loss after bariatric surgery leads to normalization of TSH levels in most patients and none developed overt hypothyroidism. Obese patients with SCH should not be treated with thyroid hormone replacement. Serial monitoring of thyroid function after obesity therapy seems to be a reasonable approach.

The Relationship between Thyroid Function and Different Obesity Phenotypes in Korean Euthyroid Adults

BACKGROUND

Thyroid disease and metabolic syndrome are both associated with cardiovascular disease. The aim of this study was to investigate the correlation between thyroid hormones and obesity sub-phenotypes using nationwide data from Korea, a country known to be iodine replete.

METHODS

This study was based on data obtained from the sixth Korea National Health and Nutrition Examination Survey, administered from 2013 to 2015. A total of 13,873 participants aged ≥19 years were included, and classified into four groups: metabolically healthy non-obesity (MHNO), metabolically healthy obesity (MHO), metabolically unhealthy non-obesity (MUNO), and metabolically unhealthy obesity (MUO) by body fat on the basis of body mass index and metabolic health.

RESULTS

At baseline, serum free thyroxine (fT4) values were significantly higher in the MHNO phenotype (MHNO, 1.27±0.01 ng/dL; MHO, 1.25±0.01 ng/dL; MUNO, 1.24±0.01 ng/dL; MUO, 1.24±0.01 ng/dL, P<0.001) in total study population. However, this significant association no longer remained after adjustment for age, urine iodine concentration, and smoking (P=0.085). After adjustment for confounders, statistically significant association was observed between lower thyroid stimulating hormone (TSH) and MHNO phenotype (P=0.044). In men participants (not women), higher fT4 values were significantly associated with MHNO phenotype (P<0.001). However, no significant association was observed between thyroid function (TSH or fT4) and obesity phenotypes in groups classified by age (cutoff age of 55 years).

CONCLUSION

Although there was a difference by age and sex, we found that the decrease of TSH and the increase of fT4 values were associated with MHNO.

GEOFFREY HARRIS PRIZE LECTURE 2018: Novel pathways regulating neuroendocrine function, energy homeostasis and metabolism in humans

The discovery of leptin, an adipocyte-secreted hormone, set the stage for unraveling the mechanisms dictating energy homeostasis, revealing adipose tissue as an endocrine system that regulates appetite and body weight. Fluctuating leptin levels provide molecular signals to the brain regarding available energy reserves modulating energy homeostasis and neuroendocrine response in states of leptin deficiency and to a lesser extent in hyperleptinemic states. While leptin replacement therapy fails to provide substantial benefit in common obesity, it is an effective treatment for congenital leptin deficiency and states of acquired leptin deficiency such as lipodystrophy. Current evidence suggests that regulation of eating behavior in humans is not limited to homeostatic mechanisms and that the reward, attention, memory and emotion systems are involved, participating in a complex central nervous system network. It is critical to study these systems for the treatment of typical obesity. Although progress has been made, further studies are required to unravel the physiology, pathophysiology and neurobehavioral mechanisms underlying potential treatments for weight-related problems in humans.

Mutations in IRS4 are associated with central hypothyroidism

BACKGROUND

Four genetic causes of isolated congenital central hypothyroidism (CeH) have been identified, but many cases remain unexplained. We hypothesised the existence of other genetic causes of CeH with a Mendelian inheritance pattern.

METHODS

We performed exome sequencing in two families with unexplained isolated CeH and subsequently Sanger sequenced unrelated idiopathic CeH cases. We performed clinical and biochemical characterisation of the probands and carriers identified by family screening. We investigated IRS4 mRNA expression in human hypothalamus and pituitary tissue, and measured serum thyroid hormones and Trh and Tshb mRNA expression in hypothalamus and pituitary tissue of Irs4 knockout mice.

RESULTS

We found mutations in the insulin receptor substrate 4 (IRS4) gene in two pairs of brothers with CeH (one nonsense, one frameshift). Sequencing of IRS4 in 12 unrelated CeH cases negative for variants in known genes yielded three frameshift mutations (two novel) in three patients and one male sibling. All male carriers (n=8) had CeH with plasma free thyroxine concentrations below the reference interval. MRI of the hypothalamus and pituitary showed no structural abnormalities (n=12). 24-hour thyroid-stimulating hormone (TSH) secretion profiles in two adult male patients showed decreased basal, pulsatile and total TSH secretion. IRS4 mRNA was expressed in human hypothalamic nuclei, including the paraventricular nucleus, and in the pituitary gland. Female knockout mice showed decreased pituitary Tshb mRNA levels but had unchanged serum thyroid hormone concentrations.

CONCLUSIONS

Mutations in IRS4 are associated with isolated CeH in male carriers. As IRS4 is involved in leptin signalling, the phenotype may be related to disrupted leptin signalling.

Thyroid Function in Korean Adolescents with Obesity: Results from the Korea National Health and Nutrition Examination Survey VI (2013-2015)

PURPOSE

In this study, we investigated the status of thyroid function and its association with metabolic risk factors in Korean adolescents.

METHODS

Among 2679 subjects aged 10-19 years who participated in the Korea National Health and Nutrition Examination Survey VI (2013-2015), 1067 adolescents (M = 559, F = 508) with available data on free T4 (FT4) and thyroid-stimulating hormone (TSH) were included. Study participants were classified into normal weight [body mass index (BMI) below 85th percentile, 80.7%], overweight (85th ≤ BMI< 95th percentile, 8.7%), and obesity (BMI ≥ 95th percentile, 10.6%).

RESULTS

With increasing levels of BMI category, the means of TSH increased (2.73 ± 0.06, 2.77 ± 0.02, and 3.24 ± 0.22 mIU/L, P = 0.031) and FT4 decreased (1.30 ± 0.01, 1.26 ± 0.02, and 1.25 ± 0.02 ng/mL, P = 0.001). Positive linear associations were observed between TSH and BMI z-score (P = 0.031), waist circumference (P = 0.013), waist-height ratio (P = 0.002), systolic blood pressure (P = 0.001), total cholesterol (P = 0.008), and triglyceride (P = 0.002) after adjusting for age and sex. With per-unit increase in TSH, the odds ratios of having abdominal obesity (OR = 1.18, 95% CI, 1.01-1.38) and triglyceride ≥ 150 mg/dL (OR = 1.18, 95% CI, 1.04-1.34) were significantly increased after adjusting for age, sex, and BMI.

CONCLUSIONS

In adolescents with obesity, TSH was higher and FT4 was lower than in adolescents with normal weight. Hyperthyrotropinemia was associated with abnormal metabolic risk factors including abdominal obesity and elevated triglyceride.

Improved Thyroid Hypoechogenicity Following Bariatric-Induced Weight Loss in Euthyroid Adults With Severe Obesity-a Pilot Study

Background: Obesity may affect both biochemical thyroid function tests; and thyroid morphology, as assessed using ultrasound scans (US). The aim of the present pilot study was to explore whether weight loss achieved by bariatric surgery alters thyroid US morphology including gray-scale measurements; and/or function in euthyroid adults with severe obesity. Methods: Euthyroid adults (>18 years) with body mass index (BMI) ≥40 kg/m² and negative thyroid peroxidase antibodies were assessed at baseline (pre-surgery) and after achieving at least 5% weight loss of their baseline body weight following bariatric surgery. Anthropometric assessments, biochemical/hormonal measurements (TSH, free-T4, free-T3, reverse-T3, and leptin) and thyroid US with gray-scale histogram analysis were performed at the baseline and post-surgery follow-up. Results: Ten Caucasian, euthyroid patients (women/men: 8/2; age: 48.6 ± 3.1 years; BMI: 51.4 ± 1.8 kg/m²) successfully completed this study with significantly decreased body weight (>5% weight loss), waist circumference and serum leptin levels post-surgery (mean post-surgery follow-up duration: 16.5 ± 2.5 months). In parallel to the observed bariatric-induced weight loss, thyroid US echogenicity increased by 25% (p = 0.03), without significant changes in thyroid volume. No significant changes in thyroid function tests were detected. No significant correlations were observed between the increase in thyroid echogenicity and the decreases in anthropometric parameters and circulating leptin. Conclusion: Our results indicate that in euthyroid adults with severe obesity, marked weight loss achieved by bariatric surgery is associated with a parallel significant increase in the thyroid US echogenicity, suggesting that morphological changes of the thyroid in obesity are reversible with weight loss. Clinical Trial Registration: www.ClinicalTrials.gov, identifier: NCT03048708.

Regulatory aspects of the human hypothalamus-pituitary-thyroid axis

Thyroid hormones are essential for growth, differentiation and metabolism during prenatal and postnatal life. The hypothalamus-pituitary-thyroid (HPT)-axis is optimized for these actions. Knowledge of this hormonal axis is derived from decades of experiments in animals and man, and more recently from spontaneous mutations in man and constructed mutations in mice. This review examines the HPT-axis in relation to 24 h TSH profiles in men in various physiological and pathophysiological conditions, including obesity, age, longevity, and primary as well as central hypothyroidism. Hormone rhythms can be analyzed by quantitative methods, e.g. operator-independent deconvolution, approximate entropy and fitting the 24-h component by Cosinor analysis or related procedures. These approaches have identified some of the regulatory components in (patho)physiological conditions.

Reference values for TSH may be inadequate to define hypothyroidism in persons with morbid obesity: Di@bet.es study

OBJECTIVE

To analyze the reference range of thyroid-stimulating hormone (TSH) in different BMI categories and its impact on the classification of hypothyroidism.

METHODS

The study included 3,928 individuals free of thyroid disease (without previous thyroid disease, no interfering medications, TSH <10 µUI/mL and thyroid peroxidase antibodies [TPO Abs] <50 IU/mL) who participated in a national, cross-sectional, population-based study and were representative of the adult population of Spain. Data gathered included clinical and demographic characteristics, physical examination, and blood and urine sampling. TSH, free thyroxine, free triiodothyronine, and TPO Ab were analyzed by electrochemiluminescence (E170, Roche Diagnostics, Basel, Switzerland).

RESULTS

The reference range (p2.5-97.5) for TSH was estimated as 0.6 to 4.8 µUI/mL in the underweight category (BMI<20 kg/m² ), 0.6 to 5.5 µUI/mL in the normal-weight category (BMI 20-24.9 kg/m² ), 0.6 to 5.5 µUI/mL in the overweight category (BMI 25-29.9 kg/m² ), 0.5 to 5.9 µUI/mL in the obesity category (BMI 30-39.9 kg/m² ), and 0.7 to 7.5 µUI/mL in the morbid obesity category (BMI ≥40). By using the reference criteria for the normal-weight population, the prevalence of high TSH levels increased threefold in the morbid obesity category (P < 0.01).

CONCLUSIONS

Persons with morbid obesity might be inappropriately classified if the standard ranges of normality of TSH for the normal-weight population are applied to them.

Effects of 17β-estradiol on leptin signaling in anterior pituitary of ovariectomized rats

Leptin is secreted predominantly by adipocytes and exerts its role mainly by interaction with the long form of leptin receptor (LEPR_V2). It has been identified that LEPR_V2 is widely distributed in various tissues, including the anterior pituitary. Cross-talk between leptin and estrogens has been indentified. Estrogen is known to modulate the tissue-specific expression of LEPR_V2 and leptin in ovariectomized (OVX) rats, a model of postmenopausal condition. Our previous data showed that 17β-estradiol (E₂) up-regulated the expression of LEPR_V2 protein and mRNA in rat dorsal root ganglion (DRG) in an estrogen receptor alpha (ERα)-dependent manner. But it is still unclear whether estrogen can regulate leptin signalling in the pituitary of OVX rats. In the present study, we found that ovariectomy decreased the expressions of LEPR_V2. Administration of E₂ increased the expressions of LEPR_V2 in a dose-dependent manner. In addition, E₂ improved LEPR_V2, STAT3, and SOCS3 protein levels in OVX rats. The effects of exogenous E₂ were attenuated by ICI 182,780, a specific estrogen receptors antagonist. However, E₂ did not change the Lepr_v1, a type of short form of leptin receptor (LEPR), or leptin mRNA levels. Thus, E₂ plays a crucial role in regulating pituitary sensitivity to leptin in OVX rats. Our findings implied that exogenous E₂ had potential roles in modification of the function of pituitary in postmenopausal women.

Early pregnancy thyroid hormone reference ranges in Chilean women: the influence of body mass index

OBJECTIVE

Thyroid dysfunction and obesity during pregnancy have been associated with negative neonatal and obstetric outcomes. Thyroid hormone reference ranges have not been established for the pregnant Hispanic population. This study defines thyroid hormone reference ranges during early pregnancy in Chilean women and evaluates associations of body mass index (BMI) with thyroid function.

DESIGN, PATIENTS, MEASUREMENTS

This is a prospective observational study of 720 healthy Chilean women attending their first prenatal consultation at an outpatient clinic. Thyroid function [TSH, Free T4, Total T4 and antithyroid peroxidase antibodies (TPOAb)] and BMI were assessed at 8·8 ± 2·4 weeks of gestational age.

RESULTS

Median, 2·5th percentile (p2·5), and 97·5th percentile (p97·5) TSH values were higher, while median, p2·5, and p97·5 free T4 values were lower in obese patients compared with normal weight patients. Obesity was associated with a median TSH 16% higher (P = 0·035) and a median free T4 6·5% lower (P < 0·01) than values from patients with normal weight. BMI had a small, but statistically significant effect on TSH (P = 0·04) and free T4 (P < 0·01) when adjusted by maternal age, TPO antibodies, parity, sex of the newborn, gestational age and smoking. In all TPOAb (-) patients, median (p2·5-p.97·5) TSH was 1·96 mIU/l (0·11-5·96 mIU/l) and median (p2·5-p.97·5) free T4 was 14·54 pmol/l (11·1 - 19·02 pmol/l). Applying these reference limits, we found a prevalence of overt and subclinical hypothyroidism of 0·9% and 3·05% respectively.

CONCLUSIONS

TSH distributes at higher values and free T4 at lower values in obese pregnant women compared to normal weight pregnant women. Thyroid hormone reference ranges derived from Chilean patients with negative TPOAb are different from the fixed internationally proposed reference ranges and may be used in the Hispanic population.

Elevated thyroid stimulating hormone levels are associated with metabolic syndrome in a Chinese community-based population of euthyroid people aged 40 years and older

This study investigated whether high-normal thyrotropin (TSH) levels are associated with metabolic syndrome in euthyroid Chinese people≥40 years old. Clinical and metabolic factors were assessed in 2,356 subjects (40-77 years old) with TSH levels in the normal range (0.35-5.00 mU/L). Using 2.50 mU/L as the cut-off point of TSH level within the normal range, we divided subjects into the high-TSH (2.50-5.00 mU/L; n = 1,064) and low-TSH (0.35-2.50 mU/L; n = 11,292) group. The results showed that the mean levels of body mass index (BMI), total cholesterol (TC), low density lipoprotein cholesterol (LDL-C), and fasting plasma glucose (FPG) were higher in the high-TSH group and TSH levels were significantly positively correlated with BMI, LDL-C, TC, and FPG. The prevalence of central obesity, hypertriglyceridemia, low high density lipoprotein cholesterol (HDL-C), and high FPG (>5.60 mmol/L) was significantly higher in females and subjects with high-TSH levels. Metabolic syndrome was also more prevalent in the high-TSH group. People over the age of 40 years with high-normal TSH levels had a 1.2-fold increased risk of metabolic syndrome, compared with those with low-normal TSH levels, after adjusting for age and gender. In conclusion, high normal TSH is a risk factor for metabolic syndrome in people≥40 years old.

The Sleep/Wake Cycle is Directly Modulated by Changes in Energy Balance

STUDY OBJECTIVES

The rise in obesity has been paralleled by a decline in sleep duration in epidemiological studies. However, the potential mechanisms linking energy balance and the sleep/wake cycle are not well understood. We aimed to examine the effects of manipulating energy balance on the sleep/wake cycle.

METHODS

Twelve healthy normal weight men were housed in a clinical research facility and studied at three time points: baseline, after energy balance was disrupted by 2 days of caloric restriction to 10% of energy requirements, and after energy balance was restored by 2 days of ad libitum/free feeding. Sleep architecture, duration of sleep stages, and sleep-associated respiratory parameters were measured by polysomnography.

RESULTS

Two days of caloric restriction significantly increased the duration of deep (stage 4) sleep (16.8% to 21.7% of total sleep time; P = 0.03); an effect which was entirely reversed upon free feeding (P = 0.01). Although the apnea-hypopnea index stayed within the reference range (< 5 events per hour), it decreased significantly from caloric restriction to free feeding (P = 0.03). Caloric restriction was associated with a marked fall in leptin (P < 0.001) and insulin levels (P = 0.002). The fall in orexin levels from baseline to caloric restriction correlated positively with duration of stage 4 sleep (Spearman rho = 0.83, P = 0.01) and negatively with the number of awakenings in caloric restriction (Spearman rho = -0.79, P = 0.01).

CONCLUSIONS

We demonstrate that changes in energy homeostasis directly and reversibly impact on the sleep/wake cycle. These findings provide a mechanistic framework for investigating the association between sleep duration and obesity risk.

Leptin and Hormones: Energy Homeostasis

Leptin, a 167 amino acid adipokine, plays a major role in human energy homeostasis. Its actions are mediated through binding to leptin receptor and activating JAK-STAT3 signal transduction pathway. It is expressed mainly in adipocytes, and its circulating levels reflect the body's energy stores in adipose tissue. Recombinant methionyl human leptin has been FDA approved for patients with generalized non-HIV lipodystrophy and for compassionate use in subjects with congenital leptin deficiency. The purpose of this review is to outline the role of leptin in energy homeostasis, as well as its interaction with other hormones.

Focus on BMI and subclinical hypothyroidism in adolescent girls first examined for amenorrhea or oligomenorrhea. The emerging role of polycystic ovary syndrome

BACKGROUND

Primary amenorrhea, oligomenorrhea and secondary amenorrhea are diagnosed commonly during adolescence. Weight aberrations are associated with menstrual disorders. Autoimmune thyroiditis is frequent during adolescence. In this study, the commonest clinical and hormonal characteristics of amenorrhea or oligomenorrhea during adolescence were investigated.

METHODS

In this cross-sectional study, one hundred and thirty-eight consecutive young patients presenting with amenorrhea or oligomenorrhea referred to an adolescent endocrinology and gynecology university clinic were studied. Clinical examination and an abdominal ultrasound were performed. Testosterone, free-testosterone, estradiol (E2), follicle stimulating hormone (FSH), luteinizing hormone (LH), prolactin (PRL), dehydroepiandrosterone sulfate (DHEA-S), 17-OH progesterone, sex hormone binding globulin (SHBG), Δ4-androstenedione (Δ4A), free androgen index (FAI), insulin, glucose, thyroid stimulating hormone (TSH), total thyroxine (T4) (TT4), free T4 (FT4), total triiodothyronine (T3) (TT3) and free T3 (FT3). Concentrations were measured in blood samples.

RESULTS

Patients with primary and secondary amenorrhea presented more often with body mass index (BMI) <18.5 and BMI >25 kg/m2, respectively. BMI values correlated positively with insulin (r=0.742) and glucose (r=0.552) concentrations and negatively with glucose/insulin ratio values (r=-0.54); BMI values and insulin concentrations correlated positively with FAI values (r=0.629 and r=0.399, respectively). In all patients, BMI values correlated positively and negatively with free testosterone (r=0.249) and SHBG (r=-0.24) concentrations, respectively. In patients with secondary amenorrhea insulin concentrations correlated negatively with SHBG concentrations (r=-0.75). In patients with oligomenorrhea BMI values correlated positively with insulin (r=0.490) and TSH (r=0.325) concentrations, and negatively with SHBG (r=-0.33) concentrations. Seventy-two percent, 21% and 7% of patients presented with TSH concentrations <2.5 μIU/mL, between 2.5 μIU/mL, 4.5 μIU/mL and >4.5 μIU/mL (subclinical hypothyroidism), respectively. Following the definition of polycystic ovary syndrome (PCOS) according to either the National Institutes of Health (NIH) criteria or those proposed in the literature by Carmina and his team, patients presented mainly with oligomenorrhea or secondary amenorrhea. There was good agreement between patients with amenorrhea or oligomenorrhea fulfilling both of the PCOS definition criteria employed.

CONCLUSIONS

Among adolescent patients presenting with amenorrhea or oligomenorrhea for the first time those with low and high BMI present more often with primary and secondary amenorrhea, respectively. Obesity is involved in the development of hyperandrogenemia and hyperinsulinemia, particularly in PCOS patients. In these patients, subclinical hypothyroidism may be concealed and it should be investigated. These patients should be treated for abnormally increased or decreased BMI and be investigated for autoimmune thyroiditis.

Serum leptin concentration in women of reproductive age with euthyroid autoimmune thyroiditis

INTRODUCTION

Autoimmune thyroid disease (AITD) with elevated anti-thyroid peroxidase antibody (aTPO) levels appears in 12-25% of all women, apart from thyroid dysfunction. High titers of aTPO are more common in women with polycystic ovary syndrome and endometriosis. Elevated aTPO has been associated with infertility and poorer quality of life among euthyroid women, and may be related to other factors.

OBJECTIVES

The aim of the study was to measure differences in serum leptin concentration between AITD+ and AITD- patients. Setting, patients and main outcome measures: The sample was comprised of 74 women who were hospitalized in the Department of Gynecological Endocrinology, Medical University of Warsaw. Data collected included age, body mass index (BMI), and serum aTPO, serum thyroid stimulating hormone (TSH), serum fT4, serum follitropin (FSH), serum estradiol and serum leptin. AITD positive status was defined as serum aTPO greater than 5.6 mIU/ml.

RESULTS

Serum leptin concentrations were significantly higher in AITD+ patients compared to AITD- patients (17.13 ng/ml [SD 7.66] versus 12.78 ng/ml [SD 7.28]; p < 0.05). No differences by AITD status were found in age, BMI, TSH, FSH, estradiol and fT4.

CONCLUSIONS

Serum leptin concentrations were higher in patients with AITD than in patients without AITD.

Metformin Decreases Thyroid Volume and Nodule Size in Subjects with Insulin Resistance: A Preliminary Study

OBJECTIVE

The aim of this study was to investigate the effects of metformin on thyroid volume and nodule size.

SUBJECTS AND METHODS

Prospective data were gathered on 100 newly diagnosed subjects with insulin resistance (68 female, 32 male) between August 2008 and May 2010. Each subject followed a standard diet and exercise program, and received 1,700 mg/day of metformin therapy for 6 months. The height, weight, waist circumference (WC) and thyroid hormone levels of each subject were measured. Additionally, the dimensions of the thyroid lobes and maximum diameter of each thyroid nodule were determined by ultrasonography. BMI and thyroid volumes were also calculated. Insulin resistance was estimated by homeostasis model assessment. All these parameters were measured at the beginning and at the end of the treatment period.

RESULTS

BMI and WC decreased significantly after metformin therapy (34.5 ± 5.1 vs. 32.7 ± 4.8, p < 0.0001, and 106.3 ± 11.8 vs. 101.8 ± 19.0 cm, p = 0.008, respectively). Insulin resistance also decreased after metformin therapy (4.5 ± 1.9 vs. 2.9 ± 1.7, p < 0.0001). The mean thyroid volume (22.5 ± 11.2 vs. 20.3 ± 10.4 ml, p < 0.0001) and mean thyroid nodule size (12.9 ± 7.6 vs. 11.7 ± 7.2 mm, p < 0.0001) also decreased after treatment.

CONCLUSION

In subjects with insulin resistance, metformin therapy significantly decreased thyroid volume and nodule size.

Iodine deficiency is higher in morbid obesity in comparison with late after bariatric surgery and non-obese women

BACKGROUND

Iodine deficiency and obesity are worldwide-occurring health problems. Our purpose was to investigate the relationship between morbid obesity and iodine status, including subjects who lost weight after bariatric surgery.

METHODS

Ninety morbidly obese women, 90 women with at least 18 months follow-up after bariatric surgery, and 45 healthy non-obese women were recruited. Urinary iodine concentration (UIC) was measured in a spot urinary sample and expressed as the iodine-to-creatinine ratio.

RESULTS

Obese women showed a significantly lower UIC in comparison with non-obese women (96.6 (25.8-267.3) vs. 173.3 (47.0-493.6) μg/g; p < 0.001), with a lesser proportion of subjects with adequate iodine status (46.6 vs. 83.3 %, p < 0.001). The mean UIC significantly increased among women who underwent bariatric surgery before the collection of the urinary sample (96.6 (25.8-267.3) vs. 131.9 (62.9-496.4) μg/g; p < 0.001). No difference in UIC was detected between laparoscopic Roux-en-Y gastric bypass and laparoscopic sleeve gastrectomy. Univariate analysis showed that UIC negatively correlated with body mass index (BMI) (r = -0.278, p < 0.001) and positively with age (r = 0.206, p = 0.002). Finally, multiple linear regression analyses showed that BMI was independently associated with UIC (beta = -0.312, p < 0.001; R (2) = 0.166).

CONCLUSION

Obesity is an independent risk factor to iodine deficiency, almost in women. Whether more obese population needs to be considered as a vulnerable group and whether bariatric surgery can reverse iodine deficiency still remain to be elucidated.

High Body Mass Index Is an Indicator of Maternal Hypothyroidism, Hypothyroxinemia, and Thyroid-Peroxidase Antibody Positivity during Early Pregnancy

Background. Maternal thyroid dysfunction in early pregnancy may increase the risk of adverse pregnancy complications and neurocognitive deficiencies in the developing fetus. Currently, some researchers demonstrated that body mass index (BMI) is associated with thyroid function in nonpregnant population. Hence, the American Thyroid Association recommended screening thyroid function in obese pregnant women; however, the evidence for this is weak. For this purpose, our study investigated the relationship between high BMI and thyroid functions during early pregnancy in Liaoning province, an iodine-sufficient region of China. Methods. Serum thyroid stimulating hormone (TSH), free thyroxine (FT4), thyroid-peroxidase antibody (TPOAb), thyroglobulin antibody (TgAb) concentration, urinary iodine concentration (UIC), and BMI were determined in 6303 pregnant women. Results. BMI ≥ 25 kg/m² may act as an indicator of hypothyroxinemia and TPOAb positivity and BMI ≥ 30 kg/m² was associated with increases in the odds of hypothyroidism, hypothyroxinemia, and TPOAb positivity. The prevalence of isolated hypothyroxinemia increased among pregnant women with BMI > 24 kg/m². Conclusions. High BMI during early pregnancy may be an indicator of maternal thyroid dysfunction; for Asian women whose BMI > 24 kg/m² and who are within 8 weeks of pregnancy, thyroid functions should be assessed especially.

Subclinical hypothyroidism: a historical view and shifting prevalence

BACKGROUND AND AIMS

Accurate diagnosis and treatment of subclinical hypothyroidism (SCH) is challenging in clinical practice because of differing upper limits of normal (ULN) for thyroid-stimulating hormone (TSH). This review summarises the various definitions of SCH and their impact on reported SCH prevalence.

METHODOLOGY

Articles reporting the prevalence of SCH in relation to the ULN of TSH in human studies were identified through an English-language PubMed search for 'subclinical hypothyroidism,' 'prevalence,' and 'TSH' within the title and/or abstract. Relevant articles and related literature were selected for inclusion.

RESULTS

Estimates for the prevalence of SCH varied by sex, age, race/ethnicity, and geographic location (range, 0.4-16.9%). Higher rates of SCH were consistently reported in women (0.9-16.9%) and older individuals (2.7-16.9%). However, the ULN of TSH in those considered free of thyroid disease and not at risk increased progressively with age, suggesting that reports of SCH prevalence in elderly people may be overestimated. Multiple studies reported an increased risk of progression to overt hypothyroidism among individuals with elevated TSH and antithyroid antibodies.

CONCLUSIONS

Given the variable definition of SCH based on an inconsistent ULN for TSH, it is currently difficult to ascertain the true prevalence of SCH and to correctly label and treat patients with SCH; use of age-adjusted definitions may be considered when assessing prevalence. A diagnosis of SCH does not necessarily merit treatment, especially if TSH elevations are transient (i.e. not persistent for > 3-6 months) and the patient lacks other risk factors for developing overt hypothyroidism.

Leptin treatment: facts and expectations

Leptin has key roles in the regulation of energy balance, body weight, metabolism, and endocrine function. Leptin levels are undetectable or very low in patients with lipodystrophy, hypothalamic amenorrhea, and congenital leptin deficiency (CLD) due to mutations in the leptin gene. For these patients, leptin replacement therapy with metreleptin (a recombinant leptin analog) has improved or normalized most of their phenotypes, including normalization of endocrine axes, decrease in insulin resistance, and improvement of lipid profile and hepatic steatosis. Remarkable weight loss has been observed in patients with CLD. Due to its effects, leptin therapy has also been evaluated in conditions where leptin levels are normal or high, such as common obesity, diabetes (types 1 and 2), and Rabson-Mendenhall syndrome. A better understanding of the physiological roles of leptin may lead to the development of leptin-based therapies for other prevalent disorders such as obesity-associated nonalcoholic fatty liver disease, depression and dementia.

Physiology of leptin: energy homeostasis, neuroendocrine function and metabolism

Leptin is secreted by adipose tissue and regulates energy homeostasis, neuroendocrine function, metabolism, immune function and other systems through its effects on the central nervous system and peripheral tissues. Leptin administration has been shown to restore metabolic and neuroendocrine abnormalities in individuals with leptin-deficient states, including hypothalamic amenorrhea and lipoatrophy. In contrast, obese individuals are resistant to leptin. Recombinant leptin is beneficial in patients with congenital leptin deficiency or generalized lipodystrophy. However, further research on molecular mediators of leptin resistance is needed for the development of targeted leptin sensitizing therapies for obesity and related metabolic diseases.

Plasma leptin concentrations are highly correlated to emotional states throughout the day

Previous work has shown that leptin appears to regulate the plasma levels of hormones such as adrenocorticotropic hormone (ACTH) and cortisol in humans and that it has antidepressant effects in animals. It is unknown whether fluctuations in circulating leptin levels are correlated to changes in human emotions. This study was conducted to determine whether minute-to-minute fluctuations in the plasma concentrations of human leptin were associated with psychological variables. Leptin was sampled every 7 min throughout the day in 10 healthy subjects (five men and five women) studied in a clinical research center, and visual analog scales were applied every hour. We found highly significant correlations between fluctuations in plasma leptin concentrations and three psychological variables: sadness, carbohydrate craving and social withdrawal. We showed that during the course of the day increases in leptin levels are associated with decreased search for starchy foods, decreased feelings of sadness and increased social withdrawal. Our findings support the hypothesis that during the course of the day as leptin levels increase individuals subjectively feel happier (less sad) and have less inclination to interact socially. Conversely, when leptin levels decrease, we show increases in sadness and social cooperation, which might facilitate the search for food. We suggest that increased human leptin levels may promote positive feelings and that decreased leptin levels might modulate inner states that motivate and facilitate the search for nutrients.

Thyroid diseases in patients with acromegaly

Acromegaly often involves the presence of different pathologies of the thyroid gland. Long-lasting stimulation of the follicular epithelium by growth hormone (GH) and insulin-like growth factor 1 (IGF-1) can cause disorders in thyroid function, an increase in its mass and the development of goitre. Acromegalic patients present most frequently with non-toxic multinodular goitre. Nodules are more prevalent in patients with active acromegaly. It has been suggested that then thyroid size increases and it can be reduced through treatment with somatostatin analogues. The relationship between thyroid volume and the level of IGF-1 and the duration of the disease is unclear. Each acromegalic patient requires a hormonal and imaging evaluation of the thyroid when the diagnosis is made, and an accurate evaluation during further observation and treatment. Although the data concerning the co-occurrence of acromegaly and thyroid cancer still remain controversial, it is particularly important to diagnose the patient early and to rule out thyroid cancer.

Lack of association between peripheral activity of thyroid hormones and elevated TSH levels in childhood obesity

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.