Actions of progesterone:


1- It is essential for occurrence & maintenance of pregnancy.
2- Uterus:
i- It promotes secretory changes of endometrium during the secretory phase of menstrual cycle.
ii- It prepares the uterus for implantation of the fertilized ovum.
iii- It decreases uterine contractions through decreasing myometrium sensitivity to oxytocin
(Which is essential for maintenance of pregnancy)
iv- It decreases the number of estrogen receptors in the endometrium.
3- Cervix: It makes the cervical mucus thick, tenacious and cellular
4- Vagina: It makes vaginal epithelium proliferate and become infiltrated by leucocytes
5- Breast: It promotes growth of the secretory acini of the breasts.
6 - Thermogenic effect: It increases the body temperature by about 0.5 ⁰C in the second half of
menstrual cycle due to increased basal metabolic rate by about (5-10%)
7- On electrolyte and water balance:
 Progesterone in large dose, it increases Na+ and water excretion.
 But in small doses, it causes Na+ and water retention.
8- It prevents ovulation & menstruation during pregnancy: Through a negative feedback
mechanism by inhibition of LH secretion