Understanding the effect of obesity on papillary thyroid cancer: is there a need for tailored diagnostic and therapeutic management?

Body Mass Index and Sporadic Medullary Thyroid Cancer: Insights from a Large Series

Background: Excess adipose tissue has been associated with the increased prevalence and aggressiveness of many human cancers. While its role in differentiated thyroid cancer is well established, in medullary thyroid cancer (MTC), data are conflicting. We aimed to evaluate the impact of excess adipose tissue on MTC prevalence, aggressiveness at diagnosis, and outcome in a large series of patients. Methods: We evaluated 529 patients with sporadic MTC from a prospectively maintained database. Weight and height were measured in all patients at the time of surgery, and body mass index (BMI) was calculated. Therefore, patients were classified according to BMI categories suggested by the WHO for Caucasian patients. Data about somatic mutations were available in 254/529 patients (48.0%). Results: The prevalence of subjects with obesity was higher than that in the Italian general population (20.2 vs. 12.0%). Patients with obesity presented smaller tumors, lower T and N stage, and lower AJCC 8th edition stage, as well as lower preoperative calcitonin values compared to under/normal and overweight ones. The prevalence of somatic RET and RAS mutations did not differ significantly across the WHO BMI categories. At the end of follow-up, structural disease was less common in patients with obesity (15.4%) compared to under/normal (25.6%, p < 0.05) and overweight (24.1%, p = 0.079). Further surgeries for local recurrence were less common in patients with obesity (3.8%) compared to overweight ones (11.0%, p < 0.05). Survival was superimposable in the different categories of BMI. Conclusions: Among patients with sporadic MTC, there is a higher prevalence of patients with obesity compared to the general population. A higher BMI was associated with less aggressive clinical presentation and better clinical outcomes.

Environmental factors related to the origin and evolution of differentiated thyroid cancer: a narrative review

INTRODUCTION

The global incidence of thyroid cancer (TC) has increased in the last decades. While improvements in diagnosis may contribute, overdiagnosis is also a possibility. This review focuses on the epidemiology, risk factors, and immune microenvironment associated with differentiated TC (DTC).

AREAS COVERED

A search was conducted in Scielo, Scopus, and EMBASE databases, involving 72 articles. TC is the most common endocrine neoplasm, with DTC form being predominant. Its incidence has globally risen, particularly among women aged over 45. Endogenous risk factors for DTC include genetic disorders, race, age, female gender, obesity, and type 2 diabetes mellitus. Environmental risks involve ionizing radiation, whether through therapeutic treatment or environmental contamination from nuclear accidents, iodine deficiency, endocrine disruptors, residence in volcanic areas, environmental pollution, and stress. The use of anti-obesity medications remains controversial. The tumor's immune microenvironment is the histological space where tumor cells interact with host cells, crucial for understanding aggressiveness. Immunotherapy emerges as a promising intervention.

EXPERT OPINION

Recent advances in DTC management offer transformative potential, requiring collaborative efforts for implementation. Emerging areas like precision medicine, molecular profiling, and immunotherapy present exciting prospects for future exploration, shaping the next era of diagnostic and therapeutic strategies in thyroid cancer research.

Subclinical Hypothyroidism in Patients with Obesity and Metabolic Syndrome: A Narrative Review

The literature on the connection between obesity, metabolic syndrome, and subclinical hypothyroidism is critically analyzed in this narrative review. These conditions are frequently observed among adult populations and various studies and meta-analyses have assessed their association. The prevalence of subclinical hypothyroidism in obese individuals is higher than in non-obese subjects and this trend is more pronounced in unhealthy obesity phenotypes. However, the diagnosis and treatment of subclinical hypothyroidism can be difficult in obese patients. Exaggerated body fat is linked to thyroid hypoechogenicity as evident through ultrasonography and euthyroid obese people have greater TSH, FT3, and FT3/FT4 ratios than non-obese individuals in a euthyroid condition. Moreover, a reduced expression of the TSH receptor and altered function of deiodinases has been found in the adipose tissue of obese patients. Current data do not support the necessity of a pharmacological correction of the isolated hyperthyrotropinemia in euthyroid obese patients because treatment with thyroid hormone does not significantly improve weight loss and the increase in serum TSH can be reversible after hypocaloric diet or bariatric surgery. On the other hand, obesity is linked to elevated leptin levels. Inflammation can raise the risk of Hashimoto thyroiditis, which increases the likelihood that obese patients will experience overt or subclinical hypothyroidism. Both metabolic syndrome and subclinical hypothyroidism are associated with atherosclerosis, liver and kidney disease. Hence, the association of these two illnesses may potentiate the adverse effects noted in each of them. Subclinical hypothyroidism should be identified in patients with obesity and treated with appropriate doses of L-thyroxine according to the lean body mass and body weight. Randomized controlled trials are necessary to verify whether treatment of thyroid deficiency could counteract the expected risks.

Obesity and thyroid cancer risk

PURPOSE OF REVIEW

This review explores recent evidence assessing the relationship between obesity and thyroid cancer.

RECENT FINDINGS

Consistent evidence from observational studies suggests that obesity increases the risk of thyroid cancer. The relationship persists when alternative measures of adiposity are used, but the strength of association may vary according to the timing and duration of obesity and how obesity or other metabolic parameters are defined as exposures. Recent studies have reported an association between obesity and thyroid cancers that are larger or have adverse clinicopathologic features, including those with BRAF mutations, thus providing evidence that the association is relevant for clinically significant thyroid cancers. The underlying mechanism for the association remains uncertain but may be driven by disruption in adipokines and growth-signaling pathways.

SUMMARY

Obesity is associated with an increased risk of thyroid cancer, although further research is required to understand the biological mechanisms underpinning this relationship. Reducing the prevalence of obesity is predicted to lessen the future burden of thyroid cancer. However, the presence of obesity does not impact current recommendations for screening or management of thyroid cancer.