Hydroxyprogesterone caproate is a synthetic steroid hormone that is similar to medroxyprogesterone acetate and megestrol acetate.

It is an ester derivative of 17α-hydroxyprogesterone formed from c aproic acid (hexanoic acid). Mimicking the action of progesterone, hydroxyprogesterone caporate binds to and activates nuclear progesterone receptors in the reproductive system and causes the ligand-receptor complex to be translocated to the nucleus where it binds to and promotes expression of target genes.

Due to the negative feedback mechanism seen with progesterone, this agent also blocks luteinizin g hormone (LH) release from the pituitary gland, thereby leading to an inhibition of ovulation and an alteration in the cervical mucus and endometrium.

Furthermore, without stimulation of LH, estrogen release from the ovaries is stopped, hence impeding the growth of estrogen-sensitive tumor cells.