Factors influencing the levothyroxine dose in the hormone replacement therapy of primary hypothyroidism in adults

Levothyroxine (LT4) is a safe, effective means of hormone replacement therapy for hypothyroidism. Here, we review the pharmaceutical, pathophysiological and behavioural factors influencing the absorption, distribution, metabolism and excretion of LT4. Any factor that alters the state of the epithelium in the stomach or small intestine will reduce and/or slow absorption of LT4; these include ulcerative colitis, coeliac disease, bariatric surgery, Helicobacter pylori infection, food intolerance, gastritis, mineral supplements, dietary fibre, resins, and various drugs. Once in the circulation, LT4 is almost fully bound to plasma proteins. Although free T4 (FT4) and liothyronine concentrations are extensively buffered, it is possible that drug- or disorder-induced changes in plasma proteins levels can modify free hormone levels. The data on the clinical significance of genetic variants in deiodinase genes are contradictory, and wide-scale genotyping of hypothyroid patients is not currently justified. We developed a decision tree for the physician faced with an abnormally high thyroid-stimulating hormone (TSH) level in a patient reporting adequate compliance with the recommended LT4 dose. The physician should review medications, the medical history and the serum FT4 level and check for acute adrenal insufficiency, heterophilic anti-TSH antibodies, antibodies against gastric and intestinal components (gastric parietal cells, endomysium, and tissue transglutaminase 2), and Helicobacter pylori infection. The next step is an LT4 pharmacodynamic absorption test; poor LT4 absorption should prompt a consultation with a gastroenterologist and (depending on the findings) an increase in the LT4 dose level. An in-depth etiological investigation can reveal visceral disorders and, especially, digestive tract disorders

A systematic review and meta-analysis investigating the relationship between metabolic syndrome and the incidence of thyroid diseases

Purpose: To assess the prospective association between metabolic syndrome (MetS), its components, and incidence of thyroid disorders by conducting a systematic review and meta-analysis. Methods: A systematic search was performed in Ovid Medline, Embase.com, and Cochrane CENTRAL from inception to February 22, 2023. Publications from prospective studies were included if they provided data on baseline MetS status or one of its components and assessed the incidence of thyroid disorders over time. A random effects meta-analysis was conducted to calculate the odds ratio (OR) for developing thyroid disorders. Results: After full-text screening of 2927 articles, seven studies met our inclusion criteria. Two of these studies assessed MetS as an exposure (N = 71,727) and were included in our meta-analysis. The association between MetS at baseline and incidence of overt hypothyroidism at follow-up yielded an OR of 0.78 (95% confidence interval [CI]: 0.52–1.16 for two studies, I2 = 0%). Pooled analysis was not possible for subclinical hypothyroidism, due to large heterogeneity (I2 = 92.3%), nor for hyperthyroidism, as only one study assessed this association. We found evidence of an increased risk of overt (RR: 3.10 (1.56–4.64, I2 = 0%) and subclinical hypothyroidism (RR 1.50 (1.05–1.94), I2 = 0%) in individuals with obesity at baseline. There was a lower odds of developing overt hyperthyroidism in individuals with prediabetes at baseline (OR: 0.68 (0.47–0.98), I2 = 0%). Conclusions: We were unable to draw firm conclusions regarding the association between MetS and the incidence of thyroid disorders due to the limited number of available studies and the presence of important heterogeneity in reporting results. However, we did find an association between obesity at baseline and incidence of overt and subclinical hypothyroidism

Selenium status is positively associated with bone mineral density in healthy aging European men

Objective It is still a matter of debate if subtle changes in selenium (Se) status affect thyroid function tests (TFTs) and bone mineral density (BMD). This is particularly relevant for the elderly, whose nutritional status is more vulnerable. Design and Methods We investigated Se status in a cohort of 387 healthy elderly men (median age 77 yrs; inter quartile range 75-80 yrs) in relation to TFTs and BMD. Se status was determined by measuring both plasma selenoprotein P (SePP) and Se. Results The overall Se status in our population was low normal with only 0.5% (2/387) of subjects meeting the criteria for Se deficiency. SePP and Se levels were not associated with thyroid stimulating hormone (TSH), free thyroxine (FT4), thyroxine (T4), triiodothyronine (T3) or reverse triiodothyronine (rT3) levels. The T3/T4 and T3/rT3 ratios, reflecting peripheral metabolism of thyroid hormone, were not associated with Se status either. SePP and Se were positively associated with total BMD and femoral trochanter BMD. Se, but not SePP, was positively associated with femoral neck and ward's BMD. Multivariate linear analyses showed that these associations remain statistically significant in a model including TSH, FT4, body mass index, physical performance score, age, smoking, diabetes mellitus and number of medication use. Conclusion Our study demonstrates that Se status, within the normal European marginally supplied range, is positively associated with BMD in healthy aging men, independent of thyroid function. Thyroid function tests appear unaffected by Se status in this population

Traditional Chinese Medicine for Hashimoto's Thyroiditis: Focus on Selenium and Antioxidant Phytochemicals.

Hashimoto's thyroiditis (HT) is not only the most frequent autoimmune thyroid disease (AITD), but it also has a significant impact on patients' health-related quality of life (HRQoL), and it has been variably associated with differentiated thyroid carcinoma. Even though its pathogenesis is still incompletely understood, oxidative stress is believed to play an important role. Hypothyroidism related to later stages of HT can be treated with levothyroxine substitution therapy; various approaches such as selenium supplementation and iodine-restricted diets have been proposed as disease-modifying treatments for earlier stages, and even thyroidectomy has been suggested for refractory cases of painful HT. Nevertheless, many patients still report suboptimal HRQoL, highlighting an unmet medical need in this area. The concepts and approaches of traditional Chinese medicine (TCM) in treating HT are not broadly known in the West. Here, we provide an overview of TCM for HT, including combinations of TCM with selenium. We encompass evidence from clinical trials and other studies related to complex TCM prescriptions, single herbs used in TCM, and phytochemicals; wherever possible, we delineate the probable underlying molecular mechanisms. The findings show that the main active components of TCM for HT have commonly known or presumed antioxidant and anti-inflammatory activities, which may account for their potential utility in HT. Further exploring the practices of TCM for HT and combining them with evidence- and mechanism-based approaches according to Western standards may help to identify new strategies to alter the clinical course of the disease and/or to treat patients' symptoms better and improve their HRQoL

Potential Risks of Excess Iodine Ingestion and Exposure: Statement by the American Thyroid Association Public Health Committee

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/140261/1/thy.2014.0331.pd

Suplementacija s antioksidansima i serumski lipidi kod bolesnika s Graves-ovom bolesti: Učinak na LDL-kolesterol

The effect of supplementation with a fixed combination of antioxidants (beta-carotene, selenium, vitamins C and E) on serum lipids was monitored in patients with newly detected Graves\u27 disease. Measurements were made prior to the commencement of therapy and after 30 and 60 days. Patients were randomized into two groups. Test group comprised patients who received antioxidant supplementation in addition to methimazole, while patients treated with methimazole only were in the control group. The concentration of total and HDL-cholesterol increased significantly in test and control groups (p < 0.05) but these groups did not differ significantly. Concentration of LDL-cholesterol increased significantly in the test group only (p < 0.005) and was significantly different from the control group 60 days after the commencing the therapy (p < 0.005). Significant increase in the LDL-cholesterol concentration in the test group requires further investigations.U ovom istraživanju promatran je učinak suplementacije fiksnom kombinacijom antioksidansa (beta-karoten, selen, vitamin C i E) na koncentracije serumskih lipida, u odnosu na brzinu postizanja eutiroze. Mjerenja su obavljena u bolesnika s novo otkrivenom Graves-ovom bolešću liječenih metimazolom (tiamazolom) prije početka terapije, te nakon 30 i 60 dana. Bolesnici su bili randomizirani u dvije skupine. Test skupinu sačinjavali su bolesnici koji su dodatno uzimali antioksidanse, a kontrolnu skupinu bolesnici koji su uzimali samo metimazol (tiamazol). Koncentracije ukupnog i HDL-kolesterola u serumu rasle su tijekom terapije kod bolesnika iz obje skupine (p < 0,05) no, nisu se međusobno značajno razlikovale 60 dana nakon početka terapije. Kod bolesnika test skupine, koncentracija LDL-kolesterola se značajno povećala (p < 0,005) i bila je značajno različita od one u kontrolnoj skupini (p < 0,005), 60 dana nakon početka liječenja. Rezultati ovog istraživanja ukazuju da suplementacija s ovom kombinacijom antioksidansa nema značajnog utjecaja na promjene koncentracije serumskih lipida kod bolesnika s Graves-ovom bolešću 60 dana nakon početka terapije, s izuzetkom LDL-kolesterola. Zbog značajnog porasta koncentracije LDL-kolesterola kod bolesnika s Graves-ovom bolešću, koji su dodatno uzimali antioksidanse, potrebna su daljnja istraživanja u cilju pojašnjenja opisanih promjena

Trace elements in glucometabolic disorders: an update

Many trace elements, among which metals, are indispensable for proper functioning of a myriad of biochemical reactions, more particularly as enzyme cofactors. This is particularly true for the vast set of processes involved in regulation of glucose homeostasis, being it in glucose metabolism itself or in hormonal control, especially insulin. The role and importance of trace elements such as chromium, zinc, selenium, lithium and vanadium are much less evident and subjected to chronic debate. This review updates our actual knowledge concerning these five trace elements. A careful survey of the literature shows that while theoretical postulates from some key roles of these elements had led to real hopes for therapy of insulin resistance and diabetes, the limited experience based on available data indicates that beneficial effects and use of most of them are subjected to caution, given the narrow window between safe and unsafe doses. Clear therapeutic benefit in these pathologies is presently doubtful but some data indicate that these metals may have a clinical interest in patients presenting deficiencies in individual metal levels. The same holds true for an association of some trace elements such as chromium or zinc with oral antidiabetics. However, this area is essentially unexplored in adequate clinical trials, which are worth being performed