Selenium in Graves' disease

Antithyroid Drug Therapy for Graves' Disease and Implications for Recurrence

Graves' disease (GD) is the most common cause of hyperthyroidism worldwide. Current therapeutic options for GD include antithyroid drugs (ATD), radioactive iodine, and thyroidectomy. ATD treatment is generally well accepted by patients and clinicians due to some advantages including normalizing thyroid function in a short time, hardly causing hypothyroidism, and ameliorating immune disorder while avoiding radiation exposure and invasive procedures. However, the relatively high recurrence rate is a major concern for ATD treatment, which is associated with multiple influencing factors like clinical characteristics, treatment strategies, and genetic and environmental factors. Of these influencing factors, some are modifiable but some are nonmodifiable. The recurrence risk can be reduced by adjusting the modifiable factors as much as possible. The titration regimen for 12-18 months is the optimal strategy of ATD. Levothyroxine administration after successful ATD treatment was not recommended. The addition of immunosuppressive drugs might be helpful to decrease the recurrence rate of GD patients after ATD withdrawal, whereas further studies are needed to address the safety and efficacy. This paper reviewed the current knowledge of ATD treatment and mainly focused on influencing factors for recurrence in GD patients with ATD treatment.

Thyroid disorders-assessments of trace elements, clinical, and laboratory parameters

The trace elements studied in this work (Se, Cu, Zn) are the essential constituents or cofactors required to activate numerous enzymes and proteins, playing crucial role in various physiological processes. The disturbed levels of abovementioned elements may adversely affect the endocrine system, resulting in various thyroid disorders among other upsets. The aim of this study was to investigate possible associations between them and parameters of redox balance, thyroid function indices as well as clinical records (duration of disease and therapy, lag time between thyroid surgery and this study examination, LT4 dosage) in patients with different thyroid disorders, including malignant diseases of the gland. In the group of patients with papillary carcinoma, we found a statistically significant higher Cu concentration compared with controls and patients with Hashimoto disease. In the same groups, the parameter of Zn/Cu ratio demonstrated reciprocally arranged statistically significant differences. For the group of papillary cancer patients, there was a negative correlation between lag time since thyroid operation and GPX3 activity. Our data support hypothesis of indirect involvement of Zn and Cu in thyroid regulation. For selenium, lack of simple correlation between its serum level and thyroid indices implies the need for further research on other selenium status parameters more adequately depicting changes in endocrine system.

The role of selenium, vitamin C, and zinc in benign thyroid diseases and of selenium in malignant thyroid diseases: Low selenium levels are found in subacute and silent thyroiditis and in papillary and follicular carcinoma

BACKGROUND

Thyroid physiology is closely related to oxidative changes. The aim of this controlled study was to evaluate the levels of nutritional anti-oxidants such as vitamin C, zinc (Zn) and selenium (Se), and to investigate any association of them with parameters of thyroid function and pathology including benign and malignant thyroid diseases.

METHODS

This controlled evaluation of Se included a total of 1401 subjects (1186 adults and 215 children) distributed as follows: control group (n = 687), benign thyroid disease (85 children and 465 adults); malignant thyroid disease (2 children and 79 adults). Clinical evaluation of patients with benign thyroid disease included sonography, scintigraphy, as well as the determination of fT3, fT4, TSH, thyroid antibodies levels, Se, Zn, and vitamin C. Besides the routine oncological parameters (TG, TSH, fT4, ultrasound) Se was also determined in the cases of malignant disease. The local control groups for the evaluation of Se levels were taken from a general practice (WOMED) as well as from healthy active athletes. Blood samples were collected between 8:00 and 10:30 a.m. All patients lived in Innsbruck. Statistical analysis was done using SPSS 14.0. The Ho stated that there should be no differences in the levels of antioxidants between controls and thyroid disease patients.

RESULTS

Among the thyroid disease patients neither vitamin C, nor Zn nor Se correlated with any of the following parameters: age, sex, BMI, body weight, thyroid scintigraphy, ultrasound pattern, thyroid function, or thyroid antibodies. The proportion of patients with benign thyroid diseases having analyte concentrations below external reference cut off levels were 8.7% of cases for vitamin C; 7.8% for Zn, and 20.3% for Se. Low Se levels in the control group were found in 12%. Se levels were significantly decreased in cases of sub-acute and silent thyroiditis (66.4 +/- 23.1 microg/l and 59.3 +/- 20.1 microg/l, respectively) as well as in follicular and papillary thyroid carcinoma. The mean Se level in the control group was 90.5 +/- 20.8 microg/l.

CONCLUSION

The H0 can be accepted for vitamin C and zinc levels whereas it has to be rejected for Se. Patients with benign or malignant thyroid diseases can present low Se levels as compared to controls. Low levels of vitamin C were found in all subgroups of patients.

Selenium, zinc, and thyroid hormones in healthy subjects: low T3/T4 ratio in the elderly is related to impaired selenium status

Iodothyronine 5' deiodinase, which is mainly responsible for peripheral T3 production, has recently been demonstrated to be a selenium (Se)-containing enzyme. The structure of nuclear thyroid hormone receptors contains Zinc (Zn) ions, crucial for the functional properties of the protein. In the elderly, reduced peripheral conversion of T4 to T3 with a lower T3/T4 ratio and overt hypothyroidism are frequently observed. We measured serum Se and RBC GSH-Px (as indices of Se status), circulating and RBC Zinc (as indices of Zn status), thyroid hormones and TSH in 109 healthy euthyroid subjects (52 women, 57 men), carefully selected to avoid abnormally low thyroid hormone levels induced by acute or chronic diseases or calorie restriction. The subjects were subdivided into three age groups. To avoid under- or malnutrition conditions, dietary records were obtained for a sample of 24 subjects, randomly selected and representative of the whole population for age and sex. Low T3/T4 ratios and reduced Se and RBC GSH-Px activity were observed only in the older group. A highly significant linear correlation between the T3/T4 ratio and indices of Se status was observed in the older group of subjects (r = 0.54; p < 0.002, for Se; r = 0.50; p < 0.002, for RBC GSH-Px). Indices of Zn status did not correlate with thyroid hormones, but RBC Zn was decreased in older as compared with younger subjects. We concluded that reduced peripheral T4 conversion is related to impaired Se status in the elderly.