Both youngsters and adults with same-sex attraction are at greater risk for negative health outcomes. It is argued that early biological events generated by genes and prenatal sex hormones determine an individual's sexual orientation. However, despite mounting efforts, a satisfactory conclusion has not been reached and there is a need to explore alternate factors like functioning of thyroid system during pregnancy.

This study was conducted to explore the relationship between maternal thyroid dysfunction in pregnancy and same-sex attraction/gender nonconformity in the offspring.

A retrospective chart review was undertaken of 790 eligible children and adolescents who had been admitted to child psychiatry between 2005 and 2013. This population consisted of 520 (65%) males and 270 (35%) females, aged 8 to17 years. Children who were victims of sexual and physical abuse and who had mental retardation, autism and psychosis were not included.

Fifteen mothers (1.8%) were found to have a history of thyroid dysfunction during pregnancy. Sixteen youngsters (2%) had a history of same-sex attraction/gender nonconformity. Twelve overlapping cases with both same-sex attraction/gender nonconformity and maternal thyroid dysfunction during pregnancy were identified, which was extremely significant (p < 0.0001, by Fisher's exact test). The association was also significant for each sex (p < 0.0001, by Fisher's exact test).

There is evidence that thyroid gland and its hormones play a crucial role in determining sexual orientation in people. Maternal thyroid dysfunctions during pregnancy may result in homosexual orientation in the offspring.