Progesterone (A): Primarily synthesized by the corpus luteum (IV) during the menstrual cycle and by the placenta during pregnancy.
Relaxin (B): Produced by the ovary (II) and the placenta during pregnancy, aiding in ligament relaxation for childbirth preparation.
Melanocyte-stimulating hormone (C): Synthesized by the pars intermedia (I) of the pituitary gland.
Catecholamines (D): Epinephrine and norepinephrine are produced by the adrenal medulla (III).