Congenital Hypothyroidism; is There any Familial Component?

Congenital hypothyroidism (CH) is a relatively common congenital disorder in neonates. Recently, a considerable proportion of familial cases have been identified, and possible roles of autoimmune factors suggested. The aim of this study was to evaluate the abnormality of thyroid function tests in first degree relatives of CH neonates and compared it to normal population. From 2002-2007 thyroid function tests (T4 and TSH) of 194 randomly selected CH neonates borne in all 17 hospitals of the Isfahan, Iran and their first degree relatives were measured, and compared with thyroid function tests of first degree relatives of 350 normal neonates that randomly selected as sex, age and urban/rural status. Patients’ mothers and control groups were also evaluated for TPO antibody. Statistical analysis was performed by SPSS (version 11.5; SPSS Inc., Chicago, IL) and Chi Square test used to compare two groups. Thyroid function tests was measured in the first degree relative of neonates with CH (361parents, 136 siblings) and compared with control groups (665 parents, 477 siblings). Thyroid function tests were abnormal in 85 patients of case group vs. 96 patients of control group. Hypothyroidism was found on 75 and 57 person in case and control groups, respectively. In 17.3% of CH neonates mothers and 32.5% of control groups mothers TPO antibody were positive. 31.4% of CH infants had parental consanguinity that 22.6% of them had abnormal thyroid function test in their family. The study showed that abnormal thyroid function tests are significantly more frequent in the first degree relatives of CH infants than normal population (P < 0.005 for parents and P < 0.0001 for siblings). Furthermore the proportion of affected infants mothers with positive TPO-Ab was significantly lower than control groups (P = 0.005). Our study suggested that there is a possible familial and genetic component in inheritance of CH and maternal thyroid autoimmunity may not play an important role in development of CH in our area.