Soy Formula Makes Congenital Hypothyroidism Harder to Treat By Anthony J. Brown, MD NEW YORK (Reuters Health) Feb 25 - The elevated TSH levels seen with congenital hypothyroidism (CH) respond to levothyroxine more slowly when the infant is being fed soy formula rather than other diets, new research indicates. Close thyroid monitoring is a must in soy-fed infants and the levothyroxine dose may need to be increased, say the authors of the study. "Having normal thyroid function tests in infancy is critical for normal brain development," lead author Dr. S. C. Conrad, from Children's Hospital Oakland in California, told Reuters Health. "So, if something is interfering with this, it can cause significant long-term problems." Recent case reports have suggested that the use of soy formulas in CH patients may slow the resolution of abnormal thyroid function tests. "For this reason and because such formulas are becoming increasingly popular, we decided to look at the association in our patient population," Dr. Conrad said. As reported in the Archives of Disease in Childhood for January, the researchers assessed a variety of TSH parameters in 8 CH patients fed a soy diet and 70 CH patients fed a non-soy diet. The two groups were comparable in terms of the starting levothyroxine dose and the change in this dose over one year. All of the measures pointed toward a prolonged increase of TSH in the soy diet group, the investigators note. For example, normalization of TSH took a median of 150 days in the soy diet group compared with just 40 days in the control group (p = 0.02). Similarly, by 4 months, 62.5% of soy-fed infants still had an elevated TSH level compared with only 17% of controls (p = 0.01). "Clinicians treating soy-fed CH patients need to be a little bit more vigilant about checking thyroid function tests and be aware that a higher levothyroxine dose may be required," Dr. Conrad said. In terms of the mechanisms involved, Dr. Conrad said that animal studies have shown that soy interferes with the intestinal absorption of levothyroxine, resulting in fecal loss of the drug. Arch Dis Child 2004;89:37-40. *********************************************** To temporarily stop your subscription: set lactnet nomail To start it again: set lactnet mail (or digest) To unsubscribe: unsubscribe lactnet All commands go to [log in to unmask] The LACTNET mailing list is powered by L-Soft's renowned LISTSERV(R) list management software together with L-Soft's LSMTP(R) mailer for lightning fast mail delivery. For more information, go to: http://www.lsoft.com/LISTSERV-powered.html