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.

Cinacalcet as alternative treatment for primary hyperparathyroidism: achievements and prospects

Primary hyperparathyroidism (pHPT), which most frequently occurs asymptomatically, is a common endocrine disease associated with increased morbidity and mortality. The newly introduced management guidelines as well as the recent availability of the first calcimimetic offer a highly promising therapeutic option for patients with pHPT. Cinacalcet, the first available calcimimetic, increases the sensitivity of the calcium-sensing receptor (CaR) to circulating serum calcium, thereby safely reducing serum calcium and PTH concentrations in patients with mild-to-moderate pHPT, intractable disease, and also parathyroid carcinoma. Cinacalcet has proved efficient in short- and long-term controls of hypercalcemia and, though bone mineral density was not improved, the available data point to cinacalcet as the treatment of choice in non-operable patients with pHPT. These results encompass a wide spectrum of disease severity. Results are pending as to whether cinacalcet decreases mortality and morbidity in pHPT, confirmation of which would conclusively recommend this drug as a valid alternative to surgery.

Environmental factors and thyroid autoimmunity

Thyroid autoimmune disease, a multifactorial organ-specific autoimmune disorder, is marking a constant increase worldwide. It is thought to be caused by multiple environmental factors triggering autoimmune response in genetically susceptible individuals, though the exact mechanisms linking environmental factors to thyroid autoimmunity are not as yet well understood. Nevertheless, there is increasing evidence that mainly nutritive factors and environmental pollution by metals and chemicals (e.g. organochlorines, pesticides) are the main factors in the present-day spread of this disease. This review presents an overview of the current knowledge regarding environmental factors, their association with genetics and their impact on the immune system.

New insights into subclinical hypothyroidism and cardiovascular risk

Subclinical hypothyroidism (SH) is a frequent condition affecting millions of people around the world. Defined by increased thyrotropin-stimulating hormone (TSH) and accompanied by normal thyroid hormone levels, SH reflects a mild tissue hypothyroidism that has been associated with metabolic derangements and-although this issue is still contentious-possibly with increased cardiovascular risk. Depending on the degree of TSH elevation, SH has accordingly been associated with hyperlipidemia, arterial hypertension, and cardiovascular disease (CVD), as well as, increasingly, newly emerging CVD risk factors such as serum C-reactive protein and retinol binding protein 4 levels. There have also been reports of abnormalities in glucose metabolism and of hemostatic parameters, mainly underscored by the increased activity of factor VII. This review discusses the results of the latest studies on the various parameters affected by SH while highlighting the need for timely treatment with levothyroxine.

Metformin: its emerging role in oncology

Metformin is considered, in conjunction with lifestyle modification, as a first-line treatment modality for type 2 diabetes mellitus (DM). Recently, several clinical studies have reported reduced incidence of neoplastic diseases in DM type 2 patients treated with metformin, as compared to diet or other antidiabetic agents. Moreover, in vitro studies have disclosed significant antiproliferative and proapoptotic effects of metformin on different types of cancer. Metformin acts by activating AMP-activated protein kinase (AMPK), a key player in the regulation of energy homeostasis. Moreover, by activating AMPK, metformin inhibits the mammalian target of rapamycin complex 1 (mTORC1) resulting in decreased cancer cell proliferation. Concomitantly, metformin induces activation of LKB1 (serine/threonine kinase 11), a tumor suppressor gene, which is required for the phosphorylation and activation of AMPK. These new encouraging experimental data supporting the anti-cancer effects of metformin urgently require further clinical studies in order to establish its use as a synergistic therapy targeting the AMPK/mTOR signaling pathway.

Selenium and the thyroid: a close-knit connection

CONTEXT

The recent recognition that the essential trace element selenium is incorporated as selenocysteine in all three deiodinases has decisively confirmed the clear-cut link between selenium and thyroid function. It has additionally been established that the thyroid contains more selenium than any other tissue and that selenium deficiency aggravates the manifestation of endemic myxedematous cretinism and autoimmune thyroid disease.

EVIDENCE ACQUISITION

Clinical reports as well as a large number of biochemical articles linking selenium to thyroid have been considered. Interventional, prospective, randomized, controlled studies, including large observational studies, supplementing selenium in autoimmune thyroid disease, together with review articles published in Medline and Pubmed have undergone scrutiny. The methodological differences and variety of results emerging from these trials have been analyzed.

EVIDENCE SYNTHESIS

Evidence in support of selenium supplementation in thyroid autoimmune disease is evaluated, the results herein presented demonstrating the potential effectiveness of selenium in reducing the antithyroid peroxidase titer and improving the echostructure in the ultrasound examination. However, considerable discord remains as to who should comprise target groups for selenium treatment, who will most benefit from such treatment, the precise impact of the basal antithyroid peroxidase level, and the effect of disease duration on the treatment outcome. Clearly, further in-depth studies and evaluation are required concerning the mechanism of action of selenium as well as the choice of supplements or dietary intake.

CONCLUSIONS

Maintenance of "selenostasis" via optimal intake not only aids preservation of general health but also contributes substantially to the prevention of thyroid disease.

Sorafenib: rays of hope in thyroid cancer

BACKGROUND

Sorafenib (BAY 43-9006) is an inhibitor of multiple-receptor tyrosine kinases involved in tumor growth and angiogenesis, which can be advantageously administered orally. Initially used as monotherapy in advanced renal cell carcinoma, sorafenib was proven to increase progression-free survival while enhancing disease control. Clinical trials on sorafenib are at present ongoing for the treatment of various malignancies, including thyroid cancer (TC).

SUMMARY

Specifically, in two phase II studies recently conducted on papillary TC, although the respective results were not entirely compatible as regard partial response rate and progression-free survival, sorafenib demonstrated a relatively favorable benefit/risk profile. In another more recent phase II study, whose primary endpoint was the reinduction of radioactive iodine uptake at 26 weeks, although no reinduction of radioactive iodine uptake was observed, 59% had a beneficial response and 34% had stable disease. Sorafenib hence appears to be a valid alternative to conventional treatment of metastatic papillary TC refractory to radioiodine therapy.

CONCLUSIONS

Further prospective investigations are required to define the characteristics of tumor response to the drug and the factors inducing resistance to treatment. A major issue demanding immediate attention involves optimization of sorafenib treatment: this concerns multidrug combination with different tyrosine kinase inhibitors or immunomodulating agents with the aim of reducing doses and thereby improving drug tolerability and antineoplastic capability.

Gender, age, puberty, and BMI related changes of TSH and thyroid hormones in schoolchildren living in a long-standing iodine replete area

The aim of the work was to assess thyroid function in children and adolescents in an iodine replete area and to explore possible effects of age, gender, puberty, and adiposity. Thyrotropin (TSH), total triiodothyronine (T (3)), total thyroxine (T (4)), free thyroxine (FT (4)), and the T (4)/T (3) ratio were determined for 440 schoolchildren (200 boys and 240 girls), aged 5-18 years, living in an iodine replete region. Body Mass Index (BMI), BMI standard deviation score (BMI-SDS), and Body Surface Area (BSA) were calculated. In girls there was a negative correlation of TSH, T (3), and FT (4) values with age. In boys there was a negative correlation only of T (3) values with age. Girls had lower TSH, T (4), and T (3) values, whereas boys had only lower T (3) values at puberty compared to the prepubertal stage. Girls had lower TSH values than boys (p<0.03) only at puberty. BMI-SDS in boys and girls were 0.21 and 0.03, respectively. BMI-SDS was not related to TSH, T (4), or T (3) in either gender, whereas it was negatively related to T (4)/T (3) ratio in boys and to FT (4) in girls. We conclude that estrogens may exert a suppressive effect on the pituitary-thyroid axis after puberty. TSH values are not correlated with BMI-SDS, whereas T (4)/T (3) ratio in boys and FT (4) in girls are negatively correlated with BMI-SDS.

The 'rings of fire' and thyroid cancer

Several studies have revealed an increased incidence of thyroid cancer in volcanic areas around the world. Hawaii and the Philippines on the rim of the Pacific Ocean, where the greatest number of volcanoes are located at convergent plate boundaries, are among the regions with the highest incidence of thyroid carcinoma worldwide. Iceland is another region also rich in volcanoes in which the highest incidence of thyroid cancer in Europe is found. The common denominator of these regions is their numerous volcanoes and the fact that several constituents of volcanic lava have been postulated as being involved in the pathogenesis of thyroid cancer. This article aims at presenting pertinent data that could link a volcanic environment to thyroid cancer.

Selenium and inflammation: underlying anti-inflammatory mechanisms

The essential trace element selenium (Se), in the form of selenoproteins, plays a pivotal role in the antioxidant defense system of the cell. There is evidence that Se may confer benefits in patients with inflammatory disease and even infectious diseases like HIV. Furthermore, in patients with severe sepsis, characterized by an increase in reactive oxygen species and low endogenous anti-oxidative capacity, as well as in patients with systemic inflammatory response syndrome, Se supplementation may reduce mortality and improve the clinical outcome, respectively. The nuclear factor kappa-B (NF-kappaB) signaling pathway has been associated with enhanced inflammatory response and its activation has been significantly correlated with interleukin-6 and TNF-alpha production. Selenium may inhibit the activation of NF-kappaB by modulating selenoprotein genes expression. Moreover, Se supplementation in chronic inflammation restores the depleted hepatic and serum Se levels by increasing selenoprotein biosynthesis leading to suppressed CRP production thereby attenuating the inflammatory process. Se increases shedding of L-selectin from monocytes while decreasing soluble L-selectin, which has been reported to be associated with high mortality in patients with sepsis. These mechanisms are likely to contribute to the modulatory effects of an increased Se status on the inflammatory response. This review evaluates some apparently key mechanisms of the anti-inflammatory action of selenium and advocates Se supplementation as a modulator of inflammatory response in infectious and autoimmune disease. Prospective, randomized, controlled studies must be performed to provide a greater degree of certainty.

Does celiac disease trigger autoimmune thyroiditis?

Autoimmune thyroiditis has increased prevalence in patients with celiac disease and vice versa. new research suggests that serum transglutaminase 2 autoantibodies, which are present in patients with celiac disease, might have a role in the development of thyroid dysfunction.

Thyroid autoimmunity in schoolchildren in an area with long-standing iodine sufficiency: correlation with gender, pubertal stage, and maternal thyroid autoimmunity

BACKGROUND

A strong genetic background and gender are believed to be involved in thyroid autoimmunity (TA). The age these factors become manifest is less clear, however. The objective of the present study was to determine the prevalence of TA in children and adolescents and to determine if there are relationships between the period of onset of TA and gender and between TA and maternal autoimmunity.

METHODS

Antithyroperoxidase antibodies (anti-TPO Ab), antithyroglobulin antibodies (anti-Tg Ab), thyrotropin, thyroxine, triiodothyronine, and urinary iodine were determined in 440 healthy schoolchildren (200 boys and 240 girls), aged 5-18 years, and in 123 mothers living in an iodine-replete region.

RESULTS

The prevalence of positive anti-TPO and anti-Tg Ab was 4.6% and 4.3%, respectively. In girls, the prevalence of positive anti-TPO Ab was higher in Tanner stage II-V compared to Tanner stage I (8.2% vs. 2.2%; p < 0.05). No difference was detected with regard to anti-Tg Ab. In girls, positive anti-TPO and anti-Tg Ab levels were associated with significantly greater thyroid volume. Hypoechogenicity was detected in 52.6% and 36.8% of the children with positive anti-TPO or anti-Tg Ab, respectively (p = 0.0005). The prevalence of autoimmune thyroiditis, as defined by positive serum anti-TPO and/or anti-Tg and an echographic pattern of the thyroid gland having diffuse or irregular hypoechogenicity, was 2.5%. Mothers of anti-TPO Ab positive children had positive anti-TPO Ab more frequently compared to mothers of anti-TPO Ab negative children (82% vs. 18%; p = 0.0005). Mothers of anti-Tg Ab positive children had positive anti-Tg Ab more frequently compared to mothers of anti-Tg Ab negative children (75% vs. 25%; p = 0.0005).

CONCLUSIONS

These findings demonstrate that thyroid antibody positivity in children was significantly associated with maternal autoimmunity and their development in girls emerges at puberty. Since heredity, female gender, and puberty are strongly associated with TA, girls in families with TA should be examined at the onset of puberty.

Review on the occasion of a decade of recombinant human TSH: prospects and novel uses

The introduction of recombinant human thyroid-stimulating hormone (rhTSH) almost a decade ago represents a remarkable achievement in the history of clinical thyroidology. rhTSH now contributes substantially to the diagnostic approach to thyroid cancer, offering a reliable and safe alternative to thyroid hormone withdrawal by avoiding the morbidity of hypothyroidism. Several recent studies have also demonstrated the efficacy of radioiodine ablation of thyroid remnants after preparation with rhTSH. Moreover, the use of rhTSH in this context is associated with a lower whole body exposure to radiation compared to thyroid hormone withdrawal. Although not approved officially, rhTSH-assisted treatment of locoregional or distant metastatic disease may be the treatment of choice for patients in whom hypothyroidism may be relatively contraindicated, such as the very young and the aged, although additional efficacy studies are necessary. The compound has also been shown to be useful in the treatment of nontoxic multinodular goiter, especially when the radioiodine uptake is low. Finally, rhTSH may prove to be useful in studying the functional reserve of thyroid in the aging process, as well as the putative role of the TSH receptor in extrathyroidal tissue, such as lymphocytes, osteocytes, and adipocytes.

Cardiovascular risk and subclinical hypothyroidism: focus on lipids and new emerging risk factors. What is the evidence?

Controversy remains as to the risk of cardiovascular disease (CVD) associated with subclinical hypothyroidism (SCH), defined as an increased serum thyrotropin (TSH) concentration with normal free thyroxine and triiodothyronine levels. Substantial evidence indicates altered cholesterol and lipoprotein metabolism in SCH when serum TSH is above 10 mU/L. Observed abnormalities include elevated plasma levels of total cholesterol (TC) and low-density lipoprotein-cholesterol (LDL-C); the altered TC/high-density lipoprotein-cholesterol (HDL-C) and LDL-C/HDL-C ratios suggest a potential accelerated risk for CVD. The influence of SCH on lipids is directly proportional to the degree of TSH elevation and becomes more significant with the progression from SCH to overt disease, thereby accelerating any propensity to atherosclerosis. Although many clinicians may tend to ignore SCH with TSH levels <10, it is apparent that an enhanced CV risk could apply to these individuals, perhaps compounded by insulin resistance and amplified by the copresence of other risk factors such as endothelial dysfunction and elevated C-reactive protein.

Thyroid volume and echostructure in schoolchildren living in an iodine-replete area: relation to age, pubertal stage, and body mass index

BACKGROUND

Thyroid volume (TV) varies between geographical regions. Thus, population-specific references for TV in regions with long-standing iodine sufficiency may be more accurate than a single international reference.

AIM

The aim of the study was to determine TV and assess the prevalence of goiter and thyroid nodules in schoolchildren aged 5-18 years living in an iodine-replete area.

METHODS

Ultrasonography was used to assess TV and structure in 440 schoolchildren (200 boys and 240 girls) living in the Athens area. Urinary iodine excretion was also measured. Age, body surface area (BSA), body mass index (BMI), and Tanner stage were recorded.

RESULTS

TV was significantly correlated with age in boys (r = 0.779, p < 0.0005) and girls (r = 0.669, p < 0.0005), and with BSA in boys (r = 0.730, p < 0.0005) and girls (r = 0.623, p < 0.0005). TV increased with the progress of puberty in boys (Tanner stage I: 3.42 mL; Tanner stage II-V: 7.35 mL; p < 0.0005) and girls (Tanner stage I: 3.74 mL; Tanner stage II-V: 5.99 mL; p < 0.0005). We used the 97th percentile value as the upper limit and calculated the prevalence of goiter to be 3.2%. There was a weak correlation between TV and BMI standard deviation score only in boys (r = 0.166, p = 0.023). Boys in Tanner stage II-V had larger TV than girls had in the same pubertal stage (7.35 mL vs. 5.99 mL, p = 0.001); such a difference was not observed in Tanner stage I. The median urinary iodine was 307.83 microg I/g creatinine, indicating iodine sufficiency. There was a significant inverse correlation between TV and urinary iodine. In 5.1% of the studied subjects one or more nodules were observed, whereas in 4.1% of cases the nodules were accompanied by hypoechogenicity.

CONCLUSIONS

In healthy Greek children living in an iodine-replete area, the main determinants of TV in both boys and girls were age, BSA, and pubertal stage. The prevalence of goiter was 3.2% and that of altered echostructure was 9.2%.

Brunner's missing 'Aha experience' delayed progress in diabetes research by 200 years

In 1889, the pancreatectomy performed on a dog by Joseph von Mehring and Oskar Minkowski led to the discovery of the pancreatic origin of diabetes disease. Already 200 years before, Johann Conrad Brunner had successfully performed eight pancreatectomies on dogs and had precisely described the symptoms of polyphagia, polyuria, and polydipsia. He did not, however, recognize the association with the diabetes disease and thus missed an opportunity to accelerate the course of diabetes research by 200 years.

Short-term hypothyroidism after Levothyroxine-withdrawal in patients with differentiated thyroid cancer: clinical and quality of life consequences

Acute hypothyroidism induced by thyroid hormone withdrawal in patients with differentiated thyroid cancer during monitoring for remnant or metastatic disease, seriously affects multiple organs and systems, and especially in severe cases can impair quality of life. Indeed, it may induce untoward cardiovascular effects and can be hazardous in patients with underlying cardiovascular disease, particularly in the elderly. Moreover, acute hypothyroidism deranges the lipid profile and exacerbates neuropsychiatric illness. The introduction of recombinant human TSH (rhTSH) as a diagnostic and therapeutic tool in the care of patients with thyroid cancer has widened the scope of disease management. The use of rhTSH prevents derangement of various systems at approximately equivalent societal costs to that of withdrawal and promotes compliance while preserving the patient's normal daily functioning and productivity. Its reliability allied with its safety render this compound a valid alternative in the monitoring of patients with differentiated thyroid carcinoma as well as providing an alternative therapeutic procedure whenever LT4-withdrawal may be hazardous or in cases of patient non-compliance.