This study was published in Pediatrics 2012 Sep;130(3):e699-702
Study title and authors:
Unawareness of the effects of soy intake on the management of congenital hypothyroidism.
Fruzza AG, Demeterco-Berggren C, Jones KL.
Division of Endocrinology, Department of Pediatrics, University of California San Diego, La Jolla, California, USA. firstname.lastname@example.org
This study can be accessed at: http://www.ncbi.nlm.nih.gov/pubmed/22908106
This paper describes two patients born with hypothyroidism (hypothyroidism is a state in which the thyroid gland does not make enough thyroid hormone) who were fed soy products and continued to manifest clinical hypothyroidism despite receiving recommended doses of levothyroxine (a synthetic form of the thyroid hormone thyroxine).
(i) The first patient was diagnosed with hypothyroidism and treated with 50 µg of levothyroxine since six days of age while simultaneously starting soy formula.
(ii) At three weeks of age, she was clinically and biochemically hypothyroid.
(iii) Her soy formula was stopped and her levothyroxine dose decreased.
(iv) Three weeks later signs of hypothyroidism were resolving, and, by 10 weeks of age, her thyroid was clinically and biochemically normal.
(i) The second patient was diagnosed hypothyroid, received levothyroxine, and did well.
(ii) Over the next two years she began consuming soy milk and became profoundly hypothyroid even though her primary care physician had increased her levothyroxine dose to 112 µg/day.
(iii) She was switched to cows milk, and her thyroid function slowly normalized with decreasing doses of levothyroxine.
These two patients highlight the adverse affects soy products have on thyroid function and may cause developmental and growth delay in infants and young children.