The Effect of Soy Phytoestrogen Supplementation on Thyroid Status and Cardiovascular Risk Markers in Patients with Subclinical Hypothyroidism: A Randomized, Double-Blind, Crossover Study

Sathyapalan, Thozhukat; Manuchehri, Alireza M.; Thatcher, Natalie J; Rigby, Alan S.; Chapman, T. E.; Kilpatrick, Eric S.; Atkin, Stephen L.

doi:10.1210/jc.2010-2255

Cited by 91 publications

(85 citation statements)

References 54 publications

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“…Soy protein has been studied and may interfere with levothyroxine absorption. Sathyapalan et al(572) performed a doubleblind crossover study and demonstrated that there was an increased risk of developing OH in patients who originally had SCH, when they received a vegetarian diet (containing 30 g soy protein and 16 mg phytoestrogen) as compared to a Western diet (containing 30 g soy protein and 2 mg phytoestrogens).The use of various thyroid hormone analogs that can be purchased over the internet to enhance thyroid function is a very controversial area. TRIAC is a naturally occurring metabolite of L-T4 that has significant metabolic action.…”

mentioning

confidence: 99%

Guidelines for the Treatment of Hypothyroidism: Prepared by the American Thyroid Association Task Force on Thyroid Hormone Replacement

Jonklaas

Bianco

Bauer

et al. 2014

Thyroid

1,464

1,376

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We concluded that levothyroxine should remain the standard of care for treating hypothyroidism. We found no consistently strong evidence for the superiority of alternative preparations (e.g., levothyroxine-liothyronine combination therapy, or thyroid extract therapy, or others) over monotherapy with levothyroxine, in improving health outcomes. Some examples of future research needs include the development of superior biomarkers of euthyroidism to supplement thyrotropin measurements, mechanistic research on serum triiodothyronine levels (including effects of age and disease status, relationship with tissue concentrations, as well as potential therapeutic targeting), and long-term outcome clinical trials testing combination therapy or thyroid extracts (including subgroup effects). Additional research is also needed to develop thyroid hormone analogs with a favorable benefit to risk profile.

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mentioning

confidence: 99%

Guidelines for the Treatment of Hypothyroidism: Prepared by the American Thyroid Association Task Force on Thyroid Hormone Replacement

Jonklaas

Bianco

Bauer

et al. 2014

Thyroid

1,464

1,376

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“…A recent study of administration of soy phytoestrogen in 2 different doses to individuals with subclinical hypothyroidism found that 10% of the 60 subjects progressed to overt hypothyroidism while receiving 16 mg/day over 8 weeks. 9 This dose was selected to duplicate the amount of phytoestrogen in a vegetarian diet.…”

Section: Discussionmentioning

confidence: 99%

Unawareness of the Effects of Soy Intake on the Management of Congenital Hypothyroidism

2012

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It has been established that soy products can interfere with thyroid hormone absorption resulting in continued hypothyroidism in individuals receiving recommended levothyroxine replacement. It has also been reported that achievement of euthyroidism in hypothyroid patients using soy products requires increased doses of levothyroxine. We have observed 2 patients with congenital hypothyroidism who continued to manifest clinical hypothyroidism while receiving recommended doses of hormone and ingesting soy products. The first patient was diagnosed by newborn screening (thyroid-stimulating hormone [TSH] =169 µIU/mL) and treated with 50 µg of levothyroxine since 6 days of age while simultaneously starting soy formula. At 3 weeks of age, she was clinically and biochemically hypothyroid (thyroxine = 4.0 µg/dL, TSH = 216 µIU/mL). We stopped her soy formula and decreased her levothyroxine dose. Three weeks later signs of hypothyroidism were resolving, and, by 10 weeks of age, she was clinically and biochemically euthyroid. Another patient was diagnosed by newborn screening, received levothyroxine, and did well. She was lost to us for 2 years. During this interval she began consuming soy milk and became profoundly hypothyroid (free thyroxine <0.4 ng/dL, TSH = 248 µIU/mL), even though the primary care physician had increased her levothyroxine dose to 112 µg/day. She was switched to cow milk, and her thyroid function slowly normalized with decreasing doses of levothyroxine. These 2 patients reinforce the importance of remembering that soy products interfere with levothyroxine absorption and can endanger infants and young children with congenital hypothyroidism who are at risk for developmental and growth delay.

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“…Subgroup analyses showed that isoflavones significantly lowered CRP by 0.70 mg/L ( p = 0.003) among women with baseline CRP concentrations greater than 2.2 mg/L, which was equivalent to an approximate 22% reduction in levels of this inflammatory marker, whereas no change was noted in women with lower baseline CRP levels [164]. Subsequently published research also reported decreases in CRP in response to various soy interventions (soy protein, soyfoods or isoflavones) including studies involving participants engaged in an exercise program [165], subclinical hypothyroid patients [166], diabetic patients [167,168], patients with liver disease [169] and patients with renal disease [169,170]. Conversely however, soy was without effect in several other studies [120,160,171,172,173,174,175,176].…”

Section: Effects Of Soy Protein On Cardiovascular Disease Risk Facmentioning

confidence: 99%

“…However, clinical research published in 2012 indicates that the iodination of isoflavones is negligible and clinically irrelevant [425]. One small British study did find that modest isoflavone exposure (16 mg/day) increased the likelihood of progressing from subclinical to overt hypothyroidism [166]. These results are surprising because the progression of subclinical to overt hypothyroidism among Japanese patients is not elevated [426] nor are rates of hypothyroidism elevated in Japan [427].…”

Section: Thyroid Functionmentioning

confidence: 99%

Soy and Health Update: Evaluation of the Clinical and Epidemiologic Literature

2016

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Soyfoods have long been recognized as sources of high-quality protein and healthful fat, but over the past 25 years these foods have been rigorously investigated for their role in chronic disease prevention and treatment. There is evidence, for example, that they reduce risk of coronary heart disease and breast and prostate cancer. In addition, soy alleviates hot flashes and may favorably affect renal function, alleviate depressive symptoms and improve skin health. Much of the focus on soyfoods is because they are uniquely-rich sources of isoflavones. Isoflavones are classified as both phytoestrogens and selective estrogen receptor modulators. Despite the many proposed benefits, the presence of isoflavones has led to concerns that soy may exert untoward effects in some individuals. However, these concerns are based primarily on animal studies, whereas the human research supports the safety and benefits of soyfoods. In support of safety is the recent conclusion of the European Food Safety Authority that isoflavones do not adversely affect the breast, thyroid or uterus of postmenopausal women. This review covers each of the major research areas involving soy focusing primarily on the clinical and epidemiologic research. Background information on Asian soy intake, isoflavones, and nutrient content is also provided.

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The Effect of Soy Phytoestrogen Supplementation on Thyroid Status and Cardiovascular Risk Markers in Patients with Subclinical Hypothyroidism: A Randomized, Double-Blind, Crossover Study

Cited by 91 publications

References 54 publications

Guidelines for the Treatment of Hypothyroidism: Prepared by the American Thyroid Association Task Force on Thyroid Hormone Replacement

Guidelines for the Treatment of Hypothyroidism: Prepared by the American Thyroid Association Task Force on Thyroid Hormone Replacement

Unawareness of the Effects of Soy Intake on the Management of Congenital Hypothyroidism

Soy and Health Update: Evaluation of the Clinical and Epidemiologic Literature

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