Testosterone

Oestrogen

Oxytocin

Atypical sex chromosome patterns

Klinefelter’s syndrome

https://www.nhs.uk/conditions/klinefelters-syndrome/

Turner syndrome

https://www.nhs.uk/conditions/turner-syndrome/

Hassett et al original paper:

Learn more about Congenital Adrenal Hyperplasia (CAH)

https://www.huffpost.com/entry/gender-toys-children-toy-preferences-hormones_n_1827727