Thyroid Research - Most accessed articles

Association between primary hypothyroidism and metabolic syndrome and the role of C reactive protein: a cross - sectional study from South India

Ghanshyam Palamaner Subash Shantha — 2009-03-09T00:00:00Z

Background: Hypothyroidism (sub-clinical and overt) and metabolic syndrome are recognized risk factors for atherosclerotic cardiovascular disease. This study is an effort to identify the proposed association between these two disease entities and the risk factors involved in this association. Methods: A cross – sectional study from a tertiary care teaching hospital in Chennai city, South India. 420 patients with metabolic syndrome (NCEP – ATP III criteria) were included in the study group. 406 appropriately age and sex matched controls having no features of metabolic syndrome (0 out of the 5 criteria) were compared with the study group. The study extended over a 5 year period. TSH, FT4 were measured for both the groups using electrochemiluminescence immuno assay. HsCRP was measured for all the patients in the study group. The baseline characteristics between the groups were compared with Student's't' test. Chi-square test was used to analyze the association between metabolic syndrome and hypothyroidism (overt and sub-clinical). Logistic regression analysis was applied to identify the association between hypothyroidism and the patient characteristics in the study group. Results: Of the 420 patients in the study group, 240 were females (57.1%), 180 were males (42.9%) with mean age 51 ± 9.4 years. Of the 406 patients in the control group, 216 were females (53.2%), 190 males (46.8%) with mean age 49 ± 11.2 years. In the study group, 92 had sub-clinical hypothyroidism (SCH) (21.9%), 31 were overtly hypothyroid (7.4%) and 297 were euthyroid (70.7%). In the control group 27 patients had sub-clinical hypothyroidism (6.6%), 9 patients had overt hypothyroidism (2.2%) and 370 patients were euthyroid (91.2%). On comparison SCH (P < 0.001) and overt hypothyroidism (P < 0.001) were significantly associated with the study group as compared to the control group. Logistic regression analysis recognized the association between female gender (P = 0.021) and HsCRP (P = 0.014) with sub-clinical hypothyroidism and female gender (P = 0.01) with overt hypothyroidism in the study group. Conclusion: Hypothyroidism is associated with metabolic syndrome and females are more at risk. Metabolic syndrome patients with a raised HsCRP are at significant risk of having sub-clinical hypothyroidism.

The mechanisms of atrial fibrillation in hyperthyroidism.

Agata Bielecka-Dabrowa — 2009-04-02T00:00:00Z

Atrial fibrillation (AF) is a complex condition with several possible contributing factors. The rapid and irregular heartbeat produced by AF increases the risk of blood clot formation inside the heart. These clots may eventually become dislodged, causing embolism, stroke and other disorders. AF occurs in up to 15% of patients with hyperthyroidism compared to 4% of people in the general population and is more common in men and in patients with triiodothyronine (T3) toxicosis. The incidence of AF increases with advancing age. Also, subclinical hyperthyroidism is a risk factor associated with a 3-fold increase in development of AF. Thyrotoxicosis exerts marked influences on electrical impulse generation (chronotropic effect) and conduction (dromotropic effect). Several potential mechanisms could be invoked for the effect of thyroid hormones on AF risk, including elevation of left atrial pressure secondary to increased left ventricular mass and impaired ventricular relaxation, ischemia resulting from increased resting heart rate, and increased atrial eopic activity. Reentry has been postulated as one of the main mechanisms leading to AF. AF is more likely if effective refractory periods are short and conduction is slow. Hyperthyroidism is associated with shortening of action potential duration which may also contribute to AF.

Gender-specific regulation of response to thyroid hormone in aging.

Satoru Suzuki — 2012-01-26T00:00:00Z

Background: Similar to other systems, the endocrine system is affected by aging. Thyroid hormone, the action of which is affected by many factors, has been shown to be associated with longevity. The most useful marker for the assessment of thyroid hormone action is TSH level. Although age and gender are believed to modify the pituitary set point or response to free thyroid hormone concentration, the precise age- and gender-dependent responses to thyroid hormone have yet to be reported. Methods: We analyzed the results of 3564 thyroid function tests obtained from patients who received medication at both out- and inpatient clinics of Shinshu University Hospital. Subjects were from among those with thyroid function test results in the normal or mildly abnormal range. Based on a log-linear relationship between the concentrations of free hormones and TSH, we established the putative resistance index to assess the relation between serum free hormone and TSH levels. Results: Free thyroid hormone and TSH concentration showed an inverse log-linear relation. In males, there was a negative relationship between the free T3 resistance index and age. In females, although there were no relationships between age and free hormones, the indices were positively related to age. Conclusions: These findings indicated that there is a gender-specific response to thyroid hormone with aging. Although the TSH level is a useful marker for the assessment of peripheral thyroid hormone action, the values should be interpreted carefully, especially with regard to age- and gender-related differences.

Assessment of Japanese iodine intake based on seaweed consumption in Japan: A literature-based analysis

Theodore Zava — 2011-10-05T00:00:00Z

Japanese iodine intake from edible seaweeds is amongst the highest in the world. Predicting the type and amount of seaweed the Japanese consume is difficult due to day-to-day meal variation and dietary differences between generations and regions. In addition, iodine content varies considerably between seaweed species, with cooking and/or processing having an influence on iodine content. Due to all these factors, researchers frequently overestimate, or underestimate, Japanese iodine intake from seaweeds, which results in misleading and potentially dangerous diet and supplementation recommendations for people aiming to achieve the same health benefits seen by the Japanese. By combining information from dietary records, food surveys, urine iodine analysis (both spot and 24-hour samples) and seaweed iodine content, we estimate that the Japanese iodine intake--largely from seaweeds--averages 1,000-3,000 μg/day (1-3 mg/day).

Thyroid storm associated with Graves' disease covered by diabetic ketoacidosis, A case report

Erika Osada — 2011-04-14T00:00:00Z

Background: Thyroid storm is a condition in which multiple organ dysfunction results from failure of the compensatory mechanisms of the body owing to excessive thyroid hormone activity induced by some factors in patients with thyrotoxicosis. While diabetic ketoacidosis (DKA) is an important trigger for thyroid storm, simultaneous development of DKA and thyroid storm is rare.Case presentationA 59-year-old woman with no history of either diabetes mellitus or thyroid disease presented to our hospital because of developing nausea, vomiting and diarrhea for 2 days. Physical examination showed mild disturbance of consciousness, fever, and tachycardia. There were no other signs of thyrotoxicosis. Laboratory studies revealed elevation of random blood glucose and glycosylated hemoglobin, strongly positive of urine acetone, and metabolic acidosis. Since DKA was diagnosed, we initiated the patient on treatment with administration of insulin and adequate fluid replacement. Although the hyperglycemia and acidosis were immediately relieved, the disturbance of consciousness and tachycardia remained persistent. Levels of FT3 and FT4 were extremely high and TSH was below the detectable limit. TRAb was positive. The thyroid storm score of Burch & Wartofsky was 75/140, and the thyroid storm diagnostic criteria of the Japan Thyroid Association were satisfied. Oral administration of thiamazole, potassium iodide and propranolol resulted in immediate relief of the tachycardia.DiscussionWe encountered a case of thyroid storm associated with Graves' disease covered by DKA. Thyroid storm and DKA are both potentially fatal, and the prognosis varies depending on whether or not these conditions are detected and treated sufficiently early. The thyroid storm diagnostic criteria prepared in 2008 by the Japan Thyroid Association are very simple as compared to the Burch & Wartofsky scoring system for thyroid storm. The Japanese criteria may be useful in the diagnosis of this condition since they enable clinicians to identify a broad range of cases with thyroid storm. When dealing with cases of DKA or thyroid storm, it seems essential to bear in mind the possibility of the coexistence of these two diseases.

Hashimoto thyroiditis is more frequent than expected when diagnosed by cytology which uncovers a pre-clinical state

Anca Staii — 2010-12-20T00:00:00Z

Background: Our Thyroid-Multidisciplinary Clinic is a large referral site for thyroid diseases. Thyroid biopsies are mainly performed for thyroid cancer screening. Yet, Hashimoto thyroiditis (HT) is being too frequently diagnosed. The prevalence of HT is reported as 0.3-1.2% or twice the prevalence of type 1 diabetes. However, the prevalence of HT confirmed by cytology is still uncertain. To evaluate different aspects of thyroid physiopathology including prevalence of Hashimoto's, a database of clinical features, ultrasound images and cytology results of patients referred for FNA of thyroid nodules was prospectively developed. Methods: We retrospectively studied 811 consecutive patients for whom ultrasound guided thyroid FNA biopsies were performed at our clinic over 2.5 year period (Mar/2006-Sep/2008). Results: The analysis of our database revealed that from 761 patients, 102 (13.4%) had HT, from whom 56 (7.4%) were euthyroid or had sub-clinical (non-hypothyroid) disease, and 46 (6%) were clinically hypothyroid. Conclusions: This is the first study to show such a high prevalence of HT diagnosed by ultrasound-guided FNA. More strikingly, the prevalence of euthyroid HT, appears to be >5% similar to that of type 2 diabetes. Based on our results, there might be a need to follow up on cytological Hashimoto's to monitor for thyroid failure, especially in high risk states, like pregnancy. The potential risk for thyroid cancer in patients with biopsy-proven inflammation of thyroid epithelium remains to be established prospectively. However, it may explain the increased risk for thyroid cancer observed in patients with elevated but within normal TSH.

Do IGF-I concentrations better reflect growth hormone (GH) action in children with short stature than the results of GH stimulating tests? Evidence from the simultaneous assessment of thyroid function

Joanna Smyczynska — 2011-01-13T00:00:00Z

Background: The diagnosis of growth hormone (GH) deficiency (GHD) in short children seems unquestionable when both GH peak in stimulating tests (GHST) and IGF-I concentration are decreased. However, the discrepancies between the results of GHST and IGF-I secretion are observed. It seems purposeful to determine the significance of GHST and IGF-I assessment in diagnosing GHD. The relationship between GH secretion and thyroid function, as well as GH influence on the peripheral thyroxine (T4) to triiodothyronine (T3) deiodination, mediated by IGF-I, were identified. Thus, clear differences in thyroid function between GH-deficient and non-GH-deficient subjects should exist. Methods: Analysis comprised 800 children (541 boys), age 11.6 ± 3.1 years (mean ± SD), with short stature, in whom two (2) standard GHST (with clonidine and with glucagon) were performed and IGF-I, free T4 (FT4), free T3 (FT3) and TSH serum concentrations were assessed. The patients were qualified to the following groups: GHD - decreased GH peak in GHST and IGF-I SDS (n = 81), ISS - normal GH peak and IGF-I SDS (n = 347), low GH - normal IGF-I SDS, and decreased GH peak (n = 212), low IGF - decreased IGF-I SDS, and normal GH peak (n = 160). The relationships among the results of particular tests were evaluated. Results: In the groups with decreased IGF-I concentrations (GHD Group and low IGF Group), the more severe deficit of height was observed, together with higher TSH and FT4 but lower FT3 levels than in groups with normal IGF-I concentrations (ISS Group and low GH Group), independently of the results of GHST. TSH, FT4 and FT3 concentrations were - respectively - similar in two groups with decreased IGF-I secretion, as well as in two groups with normal IGF-I levels. Significant correlations were found between patients' height SDS and IGF-I SDS, between FT3 and IGF-I SDS (positive), and between FT4 and IGF-I SDS (negative), with no correlation between GH peak and any of the parameters analyzed. Conclusion: The assessment of thyroid function in children with short stature provides the evidence that measurement of IGF-I concentration may be a procedure reliable at least to the some degree in diagnosing GHD as the results of GHST.

Hypothyroidism and mood disorders: integrating novel insights from brain imaging techniques

2011-08-03T00:00:00Z

AbstractThyroid hormones play a critical role in brain development but also in the adult human brain by modulating metabolic activity. Hypothyroid states are associated with both functional and structural brain alterations also seen in patients with major depression. Recent animal experimental and preclinical data indicate subtle changes in myelination, microvascular density, local neurogenesis, and functional networks. The translational validity of such studies is obviously limited. Clinical evidence for neurobiological correlates of different stages and severities of hypothyroidism and effects of pharmacological intervention is lacking but may be achieved using advanced imaging techniques, e.g. functional and quantitative MRI techniques applied to patients with hypothyroidism before and after hormone replacement therapy.

Molecules important for thyroid hormone synthesis and action - known facts and future perspectives

2011-08-03T00:00:00Z

Thyroid hormones are of crucial importance for the functioning of nearly every organ. Remarkably, disturbances of thyroid hormone synthesis and function are among the most common endocrine disorders affecting approximately one third of the working German population. Over the last ten years our understanding of biosynthesis and functioning of these hormones has increased tremendously. This includes the identification of proteins involved in thyroid hormone biosynthesis like Thox2 and Dehal where mutations in these genes are responsible for certain degrees of hypothyroidism. One of the most important findings was the identification of a specific transporter for triiodothyronine (T3), the monocarboxylate transporter 8 (MCT8) responsible for directed transport of T3 into target cells and for export of thyroid hormones out of thyroid epithelial cells. Genetic disturbances of MCT8 in patients result in a biochemical constellation of high T3 levels in combination with low or normal TSH and thyroxine levels leading to a new syndrome of severe X-linked mental retardation. Importantly mice lacking MCT8 presented only with a mild phenotype, indicating that compensatory mechanisms exist in mice. Moreover, it has become clear that not only genomic actions of T3 exist. T3 is also capable to activate adhesion receptors and it signals via activation of PI3K and MAPK pathways. Most recently, thyroid hormone derivatives were identified, the thyronamines which are decarboxylated thyroid hormones initiating physiological actions like lowering body temperature and heart rate, thereby acting in opposite direction to the classical thyroid hormones. So far it is believed that thyronamines function via the activation of a G-protein coupled receptor, TAAR1. The objective of this review is to summarise the recent findings in thyroid hormone synthesis and action and to discuss their implications for diagnosis of thyroid disease and for treatment of patients.

Solitary intrathyroidal metastasis of renal clear cell carcinoma in a toxic substernal multinodular goiter

Gianlorenzo Dionigi — 2008-10-24T00:00:00Z

IntroductionThyroid gland is a rare site of clinically detectable tumor metastasis.Case reportA 71-year-old woman was referred to our department for an evaluation of toxic multinodular substernal goiter. She had a history of renal clear cell carcinoma of the left kidney, which had been resected 2 years previously. US confirmed the multinodular goiter. Total thyroidectomy with neuromonitoring was performed on March 2008. A histological examination revealed a solitary metastasis of a clear cell renal cancer in a diffuse multinodular goiter. No distant metastases are detected. Conclusion: Although uncommon, it is important for the endocrine surgeon and endocrine oncologist to be able to recognize and differentiate intrathyroid metastases from more primary common thyroid neoplasms. The diagnosis can be suspected if the patient has a thyroid tumor and a past history of extrathyroid cancer. These tumors, on the whole, tend to behave more aggressively and, in most cases, the use of multimodality therapy is recommended.