Feb 12 2004
Research was published in January showing that a diet that consists solely of soy formula can cause TSH levels to remain high in infants who have congenital hypothyroidism, even when they are being treated with levothyroxine. The study looked at the impact of a soy formula diet on thyroid function in 78 infants who were born hypothyroid, a condition known as congenital hypothyroidism.
Those infants who were fed strictly soy formula during their first year had a higher TSH levels after starting thyroid hormone replacement treatment than those infants on a non-soy diet. The median TSH levels after treatment began were 42.6 for those on a soy diet and 6.6 for those on a non-soy diet. These are substantial differences, and elevated TSH in infants may slow or impair cognitive and physical development.
The soy formula infants also saw their TSH levels return to normal more slowly. After four months of treatment, almost two-thirds of the soy formula infants still had elevated TSH levels indicative of hypothyroidism, compared to only 17% of those on the non-soy diet. The infants on the soy formula took a median of 150 days to achieve a TSH level less than 10, while those on the non-soy diet saw TSH levels drop below 10 within 40 days.
This research shows the potentially negative impact of soy formula in infants with hypothyroidism, and points to the further need for study on the connections between soy and thyroid function.
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Source: Archives of Disease in Childhood, 2004 Jan;89:1:37-40. "Soy formula complicates management of congenital hypothyroidism"
