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

Division of Endocrinology, Department of Pediatrics, University of California San Diego, La Jolla, California, USA.
PEDIATRICS (Impact Factor: 5.47). 08/2012; 130(3):e699-702. DOI: 10.1542/peds.2011-3350
Source: PubMed


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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    • "In animal research, it was shown that certain meals can cause Hashimoto-like thyroiditis [19]. Other report found that in hypothyroidism patients, the intake of soy products might interfere with the thyroid function [20]. The following case was reported by our group in which a possible soy milk triggers Hashimoto's thyroiditis. "
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    ABSTRACT: Hashimoto’s thyroiditis is an autoimmune disease with symptoms of hypothyroidism including psychosis, weight gain, heat and cold sensitivity etc. Some risk factors such as certain human leukocyte antigen (HLA), cytotoxic T-lymphocyte antigen (CTLA) polymorphisms or certain infections are related to this disease. There are some reports claiming soy food could interfere with thyroid function. In this study, we found a case that soy milk might be a possible cause of Hashimoto’s thyroiditis by collecting relevant history and laboratory data from patient. The literature reviews provide supportive proof for this claim. It is concluded that the soy milk might be an etiology of Hashimoto’s thyroiditis which can be especially alarming for Asian people who favor drinking soy milk instead of milk.

  • Journal of pediatric nursing 02/2013; 28(2). DOI:10.1016/j.pedn.2013.01.006 · 1.01 Impact Factor
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    ABSTRACT: Thyroxine hormone has been recognised since the early part of the nineteenth century and levothyroxine has been available since the mid-nineteenth century as a replacement for deficient thyroid hormones. While levothyroxine remains the staple treatment for hypothyroidism even to this day, its optimal use can be challenging. As is often the case with older drugs, the pharmacokinetics of levothyroxine is often under-appreciated or misunderstood and many factors influence the optimal dosing of levothyroxine. This article will review the pharmacokinetics of levothyroxine in the treatment of hypothyroidism and highlight major concepts that should aid both clinicians and researchers.
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