Probable histone demethylase that specifically demethylates 'Lys-9' of histone H3, thereby playing a central role in histone code. Demethylation of Lys residue generates formaldehyde and succinate. May be involved in hormone-dependent transcriptional activation, by participating in recruitment to androgen-receptor target genes (By similarity). Binds 1 Fe(2+) ion per subunit. Interacts specifically with the ligand-binding domain of the thyroid receptor (TR). Requires the presence of thyroid hormone for its interaction. Leu-Xaa-Xaa-Leu-Leu (LXXLL) motifs are known to mediate the association with nuclear receptors. May function as a tumor suppressor, reduced expression in breast cancer tumors. Belongs to the JHDM2 histone demethylase family.