OBJECTIVE: Replacement T4 dose in hypothyroid patients bearing both chronic 
autoimmune thyroiditis and atypical celiac disease (CD) has been analyzed.
DESIGN: Replacement T4 dose has been analyzed in 35 hypothyroid patients with 
Hashimoto's thyroiditis (HT) and atypical CD, as defined by the American 
Gastroenterological Association. We have evaluated the ability of the same dose 
of T4 to reach target TSH in 21 patients before and during gluten-free diet 
(GFD). In the remaining 14 patients, noncompliant with GFD, we analyzed 
replacement T4 dose and compared it with that in a similar group consisting of 
68 patients with hypothyroid HT but no evidence of celiac sprue or other 
conditions interfering with T4 absorption.
RESULTS: In patients with isolated HT, the desired serum TSH (median=1.02 
mU/liter) was reached in all patients after 5±2 months of treatment at a median 
T4 dose of 1.31 μg/kg·d. After a similar period and dose of T4, higher levels of 
TSH (median=4.20 mU/liter) were observed in patients with HT and CD. In 21 CD 
patients, target TSH (median TSH=1.25 mU/liter) has been attained after 11±3 
months of GFD without increasing T4 dose (1.32 μg/kg·d). In the remaining 14 
patients, who were noncompliant with GFD, target TSH has also been achieved but 
at a higher T4 dose (median=1.96 μg/kg·d; +49%; P=0.0002) than in hypothyroid 
patients without CD.
CONCLUSIONS: Atypical CD increases the need for T4. The effect was reversed by 
GFD or by increasing T4 dose. Malabsorption of T4 may provide the opportunity to 
detect CD that was overlooked until the patients were put under T4 therapy.