I am of the opinion, it is. See e.g.:

Simpson ER. Sources of estrogen and their importance. J Steroid Biochem Mol Biol. 2003 Sep;86(3-5):225-30.

Nelson LR1, Bulun SE. Estrogen production and action. J Am Acad Dermatol. 2001 Sep;45(3 Suppl):S116-24.

Thank you very much