Prevalence of thyroid function test abnormalities and thyroid autoantibodies in children with vitiligo.

Sir,

With reference to the interesting study by Afsar and Isleten,[1] the association of thyroid dysfunction (TD) with vitiligo has triggered studies worldwide to evaluate the justification for screening for TD in patients with certain vitiligo types. Currently, children with vitiligo, especially girls and subjects with generalized/vulgaris-type vitiligo, have been advocated to be screened annually for thyroid function tests (TFTs) and thyroid autoantibodies (TAA) to assist in the early diagnosis and therapy of associated TD.[2] Afsar and Isleten[1] stated in their study that TFT and TAA abnormalities were detected in 25.3% of the studied pediatric patients with nonsegmental vitiligo. Among them, 16.4% of patients were evaluated as subclinical hypothyroidism, 2.5% were evaluated as hypothyroidism, and 6.3% were evaluated as euthyroidism. However, TAA were found to be positive in 11.3% of patients. On the basis of these data, Afsar and Isleten[1] suggested that TFT and TAA be analyzed in children with vitiligo. I presume that such suggestion ought to be cautiously undertaken. This is based on the presence of four limitations that were not considered by Afsar and Isleten.[1] These include the followings. (1) The study period was short (21 months; April 2008-January 2010). (2) The studied cohort was small (n = 79). 3. It is well-known that reference limits for thyroid hormones (THs) and thyroid-stimulating hormone (TSH) differ between races and with age. Age- and race-specific distribution and reference limits, possibly influenced by genetic factors, should be employed to provide clinicians accurate limits for specific populations and guidance for further evaluation of TD.[3] Such references have been constructed for certain pediatric populations.[45] According to my knowledge, no similar Turkish references are yet present to be employed in the clinical settings. 4. The data addressed by Afsar and Isleten[1] were related to a single pediatric dermatology clinic. Conducting large scale multicenter studies over extended period of time and employing Turkish age- and gender-specific reference for TH and TSH could better elucidate the exact prevalence of TD in Turkish vitiligo patients and, hence, the justification to screen them for TD.