Metformin Treatment for Small Benign Thyroid Nodules in Patients with Insulin Resistance

The prevalence of thyroid nodules and its relationship with metabolic parameters in a Chinese community-based population aged over 40 years

To investigate the prevalence of thyroid nodules (TN) among a community population aged >40 years and to explore the association between TN and its metabolic risk factors. Data from 9,533 adults aged over 40 years who participated in the epidemiological investigation of thyroid nodules in a Chinese community-based population from June to December 2011 were included in the analyses. We compared the levels of metabolic indices between the TN group and healthy controls. The prevalence of TN was 46.6% (39.7%, men; 50.3%, women) and it increased significantly with increasing age (P < 0.001). It was significantly higher in the group with hypertension than in that with normotension (P < 0.001) and was 43.0% in the normal blood glucose group, 49.4% in the prediabetes group, and 50.9% in the diabetes group (P < 0.001). Logistic regression analysis indicated that hypertension [odds ratio (OR) = 1.121 (1.025-1.225)] as well as prediabetes and diabetes [OR = 1.130 (1.036-1.233)] were all independent risk factors for TN after adjustment for sex, age, body mass index, blood lipid levels, smoking status, and alcohol consumption. The elderly population had a high prevalence of TN. Hypertension as well as prediabetes and diabetes might be independent risk factors for TN.

An analysis of the relative risk for goitre in euthyroid patients with type 2 diabetes

AIM

To assess the relative risk for goitre in a cohort of euthyroid patients with type 2 diabetes with special reference to the use of metformin and insulin therapy.

PATIENTS AND METHODS

Eight hundred euthyroid patients with type 2 diabetes (433 women, mean age 65·8 ± 12·5 years) and 671 euthyroid subjects without diabetes were retrospectively evaluated. There were 250 patients on metformin and 455 patients on insulin treatment.

RESULTS

The gender-, age-, body mass index- and thyrotropin (TSH)-adjusted relative risk for goitre occurring among diabetic patients relative to controls was 3·01 (1·61-5·64) (P < 0·01). This odds ratio was significant in females, patients with and without metformin therapy, patients without insulin therapy and without micro- and macrovascular complications of diabetes. However, male pateints, patients on insulin therapy or with micro- or macroangiopathy did not exhibit an increase in the risk of goitre. Patients on metformin therapy showed a significant increase in the risk of goitre only in the absence of insulin therapy. Multi-adjusted logistic regression analysis showed that goitre was significantly related to gender, TSH and haemoglobin A1c levels. Metformin and insulin therapy were nonsignificant variables in this model.

CONCLUSION

This is the first survey analysing the relationship between the presence of palpable goitre and clinical parameters in a large cohort of patients with type 2 diabetes. Our data suggest a significant relationship between goitre and glycaemic control, but do not support the presence of independent and significant relationships between goitre and metformin or insulin treatment in euthyroid patients with type 2 diabetes.

Obesity and thyroid cancer: epidemiologic associations and underlying mechanisms

The incidence of thyroid cancer has been rising over the past few decades along with a parallel increase in obesity. Observational studies have provided evidence for a potential association between the two. By contrast, clinical data for a link between type 2 diabetes mellitus, a condition strongly associated with obesity, and thyroid cancer are limited and largely not supportive of such an association. Obesity leads to hypoadiponectinemia, a pro-inflammatory state, and insulin resistance, which, in turn, leads to high circulating insulin and insulin-like growth factor-1 levels, thereby possibly increasing the risk for thyroid cancer. Thus, insulin resistance possibly plays a pivotal role in underlying the observed association between obesity and thyroid cancer, potentially leading to the development and/or progression of thyroid cancer, through its interconnections with other factors including insulin-like growth factor-1, adipocytokines/cytokines and thyroid-stimulating hormone. In this review, epidemiological and clinical evidence and potential mechanisms underlying the proposed association between obesity and thyroid cancer risk are reviewed. If the association between obesity and thyroid cancer demonstrated in observational studies proves to be causal, targeting obesity (and/or downstream mediators of risk) could be of importance in the prevention and management of thyroid cancer.

Repositioning metformin for cancer prevention and treatment

Metformin is the most commonly prescribed drug for type 2 diabetes (T2DM). Retrospective studies show that metformin is associated with decreased cancer risk. This historical correlation has driven vigorous research campaigns to determine the anticancer mechanisms of metformin. Consolidating the preclinical data is a challenge because unanswered questions remain concerning relevant mechanisms, bioavailability, and genetic factors that confer metformin sensitivity. Perhaps the most important unanswered question is whether metformin has activity against cancer in non-diabetics. In this review we highlight the proposed mechanisms of metformin action in cancer and discuss ongoing clinical trials with metformin in cancer. Improved understanding of these issues will increase the chances for successful application of metformin as an inexpensive, well-tolerated, and effective anticancer agent.

Metformin inhibits goitrogenous effects of type 2 diabetes

OBJECTIVE

Data on the association between type 2 diabetes mellitus (T2DM) and thyroid volume are sparse. An experimental study demonstrated an inhibitory effect of metformin on the growth of human thyroid cells. So far no study on humans has investigated potentially modulating effects of metformin on the association between T2DM and thyroid volume. Therefore, we investigated these effects in a population-based cohort study.

DESIGN AND METHODS

We used data from the Study of Health in Pomerania and included 2570 individuals for cross-sectional and 1088 individuals for longitudinal analyses. T2DM was defined by physician-diagnosed self-report or intake of antidiabetic medication.

RESULTS

In the cross-sectional data, females with T2DM treated with antidiabetic medication other than metformin had a larger thyroid volume (β=4.69; 95% CI 1.87 to 7.50) and a higher odds ratio (OR) for goiter (OR=1.71; 95% CI 1.05 to 2.79) than females without T2DM, whereas in males, no such association was detected. In females or males treated with metformin, T2DM was not associated with thyroid volume or goiter. In longitudinal analyses, incident T2DM not treated with metformin was significantly associated with a higher risk for incident goiter in the total population (incidence rate ratio (IRR)=1.70; 95% CI 1.10 to 2.91). Individuals with T2DM having changed from metformin to other antidiabetic agents during follow-up also had a higher risk for incident goiter than individuals without T2DM (IRR=2.71; 95% CI 1.74 to 4.20).

CONCLUSIONS

We demonstrate an inhibitory effect of metformin on prevalent and incident goiter. Anti-goitrogenous effects of metformin add to the general benefits of metformin treatment of T2DM.

Impaired glucose metabolism is a risk factor for increased thyroid volume and nodule prevalence in a mild-to-moderate iodine deficient area

OBJECTIVE

Insulin resistance (IR) is a key factor involved in the pathogenesis of impaired glucose metabolism. IR is associated with increased thyroid volume and nodule prevalence in patients with metabolic syndrome. Data on the association of thyroid morphology and abnormal glucose metabolism are limited. This prospective study was carried out to evaluate thyroid volume and nodule prevalence in patients with pre-diabetes and type 2 diabetes mellitus (DM) in a mild-to-moderate iodine deficient area.

MATERIALS AND METHODS

Data were gathered on all newly diagnosed patients with pre-diabetes and type 2 diabetes mellitus between May 2008 and February 2010. 156 patients with pre-diabetes and 123 patients with type 2 DM were randomly matched for age, gender, and smoking habits with 114 subjects with normal glucose metabolism. Serum thyroid-stimulating hormone (TSH) and thyroid ultrasonography was performed in all participants.

RESULTS

Mean TSH level in the diabetes group (1.9±0.9 mIU/L) was higher than in the control group (1.4±0.8 mIU/L) and the pre-diabetes group (1.5±0.8 mIU/L) (P<0.0001 for both). Mean thyroid volume was higher in the pre-diabetes (18.2±9.2mL) and diabetes (20.0±8.2mL) groups than in controls (11.4±3.8mL) (P<0.0001 for both). Percentage of patients with thyroid nodules was also higher in the pre-diabetes (51.3%) and diabetes groups (61.8%) than in controls (23.7%) (P<0.0001 for both).

CONCLUSIONS

The results suggest that patients with impaired glucose metabolism have significantly increased thyroid volume and nodule prevalence.

Prevalence of goiter and thyroid nodular disease in patients with class III obesity

OBJECTIVES: To evaluate the prevalence of goiter and nodular disease in patients with class III obesity, and to correlate results with serum leptin levels and insulin resistance (IR) parameters. SUBJECTS AND METHODS: A cross-sectional study was performed to assess thyroid ultrasound (US) patterns, HOMA-IR, serum leptin, and TSH levels in obese patients and controls. RESULTS: Thyroid volume was positively correlated with body mass index (BMI) (r = 0.240, p = 0.039) and with HOMA-IR (r = 0.329; p < 0.01). Thyroid US patterns were similar between groups. However, when data from the male group was considered, greater thyroid volume was detected in the obese group compared with controls (10.8 vs. 8.5 cm³; p = 0.04). Also, nodules were more frequently detected (67% vs. 18%), as were nodules requiring FNAB (33.3% vs. 0%, p ≥ 0.05-0.09), in this group. CONCLUSION: Although IR did not correlate directly with the presence of nodules, the results support the hypothesis of a direct association between insulin resistance and thyroid volume.

Metformin and thyroid: an update

BACKGROUND

Metformin is one of the most widely prescribed antidiabetic medications with a favorable safety profile. In the last decade, several studies have reported a TSH-lowering effect of metformin in patients with diabetes mellitus.

OBJECTIVE

To review literature data on the role of metformin use on thyroid function tests and the course of thyroid cancer.

METHODS

WE PERFORMED A SEARCH IN THE PUBMED DATABASE USING THE TERMS: 'metformin', 'thyroid', 'TSH', 'diabetes', 'polycystic ovarian syndrome (PCOS)' and 'thyroid cancer'.

RESULTS

The majority of available evidence suggests that metformin therapy results in a modest reduction of TSH levels in diabetic and/or PCOS patients with thyroid disorder, while thyroid hormone levels remain unaltered. It appears that this effect is independent of thyroid autoimmunity and thyroxine treatment. However, metformin use in subjects with an intact thyroid axis is not associated with a significant change of TSH levels. Concerning thyroid cancer, there is experimental evidence showing antimitogenic properties of metformin in differentiated and medullary thyroid cancer cells. On the other hand, there is also data supporting that metformin administration inhibits iodine uptake by thyroid cells and thus may limit the effectiveness of radioactive iodine treatment.

CONCLUSIONS

Most studies suggest a TSH suppressive action of metformin in subjects with overt or subclinical thyroid dysfunction, while this is not apparent in euthyroid individuals. It appears that metformin has antimitogenic properties against various thyroid cancer types; however, experimental evidence of reduced efficacy of radioactive iodine treatment following metformin administration may limit its use in the management of differentiated thyroid cancer.

Disease-specific mortality and secondary primary cancer in well-differentiated thyroid cancer with type 2 diabetes mellitus

Background

Increased body mass index is related to the incidence of thyroid cancer. However, the presentation and therapeutic outcomes of different thyroid cancers and type 2 diabetes mellitus (DM) have not been studied. This study investigated the effect of type 2 DM on the clinical presentations and therapeutic outcome of well-differentiated thyroid cancer.

Methods and Findings

A retrospective analysis of adult thyroid cancer patients with or without type 2 DM admitted between January 2001 and December 2010 was performed at an institution. A total of 1,687 well-differentiated thyroid cancer patients with different histological patterns were enrolled. Among these subjects, 122 were type 2 DM patients. Patients with thyroid cancer and type 2 DM were significantly older than non-DM patients. After a mean follow-up period of 5.6±0.1 years, patients with thyroid cancer and type 2 DM showed a higher percentage of disease progression than non-DM patients (24.6% vs. 17.4%). In addition, disease-specific mortality was higher in the type 2 DM group (10.7% vs. 3.8%). Thyroid cancer patients with type 2 DM showed a higher percentage of secondary primary cancers than those without DM (10.7% vs. 4.9%). Thyroid cancer-specific survival rates in the type 2 DM and non-DM groups were 82.2% and 94.9% at 5 years, 72.9% and 91.4% at 10 years, and 36.5% and 61.3% at 20 years, respectively. Multivariate analysis showed that type 2 DM was independent of thyroid cancer-specific mortality.

Conclusion

Patients with type 2 DM and well-differentiated thyroid cancer had an advanced tumor-node-metastasis stage at the time of diagnosis and an increased disease-specific mortality. Aggressive surgical procedures and close follow-up for well-differentiated thyroid cancer patients with type 2 DM are therefore necessary.

Metformin and its clinical use: new insights for an old drug in clinical practice

Metformin is generally recommended as first-line treatment in type 2 diabetes, especially in overweight patients, but in recent years new indications for its use have emerged. Metformin has been found to be safe and efficacious both as monotherapy and in combination with all oral antidiabetic agents and insulins. If metformin use during pregnancy and the lactation period is supported by few data, it could be indicated for women with polycystic ovary syndrome, since it could diminish circulating androgens and insulin resistance, thus ameliorating the ovulation rate. Metformin seems to reduce cancer risk, which appears to be increased in diabetics, and is a promising agent for oncoprevention and chemotherapy combinations. Moreover, metformin could find a place in the treatment of non-alcoholic fatty liver disease. Lactic acidosis could be decreased by avoiding metformin use in patients with hypovolemia, sepsis, renal impairment, hypoxic respiratory diseases and heart failure, in the preoperative period and before intravenous injection of contrast media.

Metformin: Midlife maturity, maiden charm

Metformin is one of the most commonly prescribed drugs for management of Type 2 diabetes mellitus. It has been in use for almost five decades. Now, pharmacological properties of this agent are being exapted for use in a number of other indications. New facets of its personality are coming up, generating more interest of the scientific community in this "middle-aged" molecule. This article explores the role of metformin in cardioprotection and its hepatoprotective properties. Nephroprotective, protection against excess body fat and gonadoprotective actions, properties have also been discussed. Additionally, this manuscript briefly reviews the thyroid stimulating hormone (TSH)-lowering properties in diabetic and non-diabetic patients, besides reviewing its actions on different types of cancers. Some of these actions may become approved indications for use of metformin following generation of new evidence. Metformin still has many unexplored dimensions that deserve further exploration.

Frequency of Thyroid Nodules among Patients with Colonic Polyps

Aim. Colonic polyps and thyroid nodules are common diseases and their frequency increases with age. In the literature, there is no study investigating the coexistence of colonic polyps and thyroid nodules. Therefore, this study was designed to investigate thyroid nodule prevalence in patients with colonic polyps. Material and Methods. Sixty-six patients with colonic polyps and 146 patients without colonic polyps enrolled into the study. Age and sex matched control group was composed from patients without colonic polyps. Colonoscopic examinations, thyroid ultrasonographies were performed in all patients, and TSH were measured. Results. Male/female ratio in polyp and control groups were 40/26 versus 68/78, respectively (P = 0.058). Mean ages were similar in both groups (53.3 ± 11.4 versus, 51.8 ± 11.4, P = 0.373). Thyroid nodule was detected in 44 (66.7%) patients with polyps and in 61 (41.8%) controls (P = 0.001). Patients with adenomatous polyps had 5 or more thyroid nodules compared to patients with hyperplastic polyps (P = 0.03). Thyroid nodules were more prevalent among patients aged 50 or older compared to 50 years or less (P = 0.023). Conclusion. Thyroid nodules were detected more common in patients with colonic polyps. Further studies are needed to clarify this coexistence.

The interface between thyroid and diabetes mellitus

Thyroid disease and type 1 but also type 2 diabetes mellitus (DM) are strongly associated, and this has important clinical implications for insulin sensitivity and treatment requirements. The pathophysiological basis of this association has only recently been better elucidated. It rests on a complex interaction of common signalling pathways and, in the case of type 1 diabetes and autoimmune thyroid disease, on a linked genetic susceptibility. The pathophysiological mechanisms underlying this linked regulation are increasingly being unravelled. They are exemplified in the regulation of 5' adenosine monophosphate-activated protein kinase (AMPK), a central target not only for the modulation of insulin sensitivity but also for the feedback of thyroid hormones on appetite and energy expenditure. The present review will discuss these concepts and their consequences for the clinical care of patients with DM and thyroid disorders. Moreover, it makes reference to the added effect of metformin in suppressing TSH.