Low serum TSH levels are associated with low values of fat-free mass and body cell mass in the elderly

Thyroid Function and Anthropometric Measures: A Systematic Review and Meta-Analysis

OBJECTIVE

Although often enquired about by patients, the association of thyroid function with anthropometric measures in the general population is unclear. We summarized population-based studies and randomized controlled trials (RCTs) on the association between thyroid function and anthropometric measures.

METHODS

We systematically searched Embase, Medline (Ovid), and Cochrane Central Register of Controlled Trials from inception until June 28, 2023. We included studies in adults examining thyroid function or thyroid disease as exposure and anthropometric measures as outcome (eg, body mass index [BMI], weight). We used random effect meta-analyses to pool the results.

RESULTS

We included 64 studies in the qualitative synthesis, and 21 in the quantitative synthesis (total participants n = 107 734 for cross-sectional studies, n = 22 010 for longitudinal studies, n = 80 for RCTs). The evidence was limited and heterogeneous, particularly for longitudinal studies. Cross-sectionally, we described an association for thyroid-stimulating hormone (TSH) concentrations and BMI (B per 1 mIU/L increase of TSH = 0.21; 95% confidence interval [CI], 0.09-0.32) and for free thyroxine (FT4) and BMI (B = -0.14; 95% CI, -0.23 to -0.05). Longitudinally, increasing TSH concentrations were related to weight gain and increasing FT4 concentrations to weight loss.

CONCLUSION

We showed a relation between higher TSH concentrations and higher BMI or weight, and between higher FT4 concentrations and lower BMI or weight, although effect sizes were modest. We highlight the need of more high-quality longitudinal studies. Despite the relevance of the association between thyroid (dys-)function and anthropometric measures, evidence is scarce.

Effects of Bariatric Surgery on Sarcopenic Obesity Outcomes: A One-Year Prospective Study in Middle-Aged Women

INTRODUCTION

Sarcopenic obesity (SO) is characterised by the confluence of muscle deterioration and high adiposity. When non-surgical interventions prove insufficient, bariatric surgery (BS) becomes the primary approach. This study aimed to address BS effects on SO outcomes 1 year post-surgery among middle-aged women, also considering physical exercise's impact.

METHODS

Prospective single-centre study of 140 patients who underwent Roux-en-Y gastric bypass or sleeve gastrectomy between November 2019 and December 2022. Participants were categorised into tertiles according to SO's diagnosis and severity (group 1-patients with the most severe SO; group 2-intermediate; group 3-the least severe or without SO), calculated considering the consensus issued by ESPEN and EASO in 2022. Evaluations of clinical and biochemical parameters were conducted before and 12 months after BS, and the variation was used for comparative purposes. Body composition was assessed using bone density scans. Linear regression analysis accounted for both surgery type and baseline body mass index (BMI).

RESULTS

Before BS, SO prevalence in the overall sample was 89.3%, decreasing to 2.9% after BS. Group 1 had more body fat mass (56.9 vs 54.8 vs 50.7 kg, p < 0.001), total, trunk and leg fat at baseline and a significantly lower total skeletal muscle mass (47.2 vs 49.4 vs 51.8 kg, p < 0.001). One year post-BS, group 1 presented more weight loss (- 39.8 ± 11.4 kg, p = 0.031), BMI reduction (- 15.9 ± 4.6 kg/m2, p = 0.005) and lost more fat mass (- 32.6 vs - 30.5 vs - 27.9 kg, p = 0.005), but not total skeletal muscle mass (- 5.8 vs - 5.9 vs - 6.8 kg, p = 0.130). Remission rates for comorbidities were substantial among all groups, but more marked among patients within group 1 (type 2 diabetes mellitus 75%, hypertension 47.1% and dyslipidemia 52.8%). Engagement in physical exercise of any kind has increased post-BS (33.1% vs 79.1%).

CONCLUSION

Despite concerns about malabsorptive mechanisms potentially worsening muscle loss, patients with the most severe SO undergoing BS lost more fat mass while experiencing the smallest reduction in total skeletal muscle mass. Remission rates for comorbidities following BS were notable among all groups.

Pituitary crosstalk with bone, adipose tissue and brain

Traditional textbook physiology has ascribed unitary functions to hormones from the anterior and posterior pituitary gland, mainly in the regulation of effector hormone secretion from endocrine organs. However, the evolutionary biology of pituitary hormones and their receptors provides evidence for a broad range of functions in vertebrate physiology. Over the past decade, we and others have discovered that thyroid-stimulating hormone, follicle-stimulating hormone, adrenocorticotropic hormone, prolactin, oxytocin and arginine vasopressin act directly on somatic organs, including bone, adipose tissue and liver. New evidence also indicates that pituitary hormone receptors are expressed in brain regions, nuclei and subnuclei. These studies have prompted us to attribute the pathophysiology of certain human diseases, including osteoporosis, obesity and neurodegeneration, at least in part, to changes in pituitary hormone levels. This new information has identified actionable therapeutic targets for drug discovery.