OXT and progressive pseudorheumatoid arthropathy of childhood: According to scientific research, in the case of PPD, the main players are certain catecholamines (serotonin) [25,26], endocrine hormones, in particular oxytocin, reproductive hormones [25,28,29], stress hormones, in particular those of the hypothalamic–pituitary–adrenal (HPA) [25,28,29,30] axis and inflammatory responses [25,31,32].