Other hormonal parameters that could be used to assess stress-coping mechanisms in horses include beta-endorphine and thyroid hormones, which have been studied in healthy horses under different conditions and could add some value to further studies (Ferlazzo et al.2018a,b,c), or oxytocin which has been studied in horses used for post-traumatic stress disorder equine-assisted therapies and activities (Malinowski et al.2018). This evidence concerns the gene TG and post-traumatic stress disorder.