Progesterone interacts with specific intranuclear receptors and binds to specific DNA sequence on the genome and then, initiates transcription of a specific set of genes which is ultimately responsible for the translation of hormonal action into physiological events. Progesterone has a negative feedback action on the hypothalamo-pituitary axis, primarily on GnRH and consequently on LH secretion. Progesterone prevents the hormonal surge from hypophysis (FSH and LH) and so suppresses oestrus and ovulation. At removal progesterone falls dramatically in 1 hour allowing follicular maturation, oestrus and ovulation in a narrow window.

Progesterone is rapidly absorbed by intravaginal route. Circulating progesterone is bound to proteins in blood. Progesterone binds to corticosteroid-binding globulin (CBG) and to albumin. Progesterone is accumulated in fatty tissue due to its lipophylic properties, and in tissues/organs containing progesterone receptors. Liver is the main site of progesterone metabolism. Progesterone has a half-life of 3 hours, a Cmax of 5µg/L and a Tmax of 9h. The principal route of excretion is the faeces and the secondary route is the urine.