Progesterone: The Key Factor of the Beginning of Life

Abstract

Progesterone is the ovarian steroid produced by the granulosa cells of follicles after the LH peak at mid-cycle. Its role is to sustain embryo endometrial implantation and ongoing pregnancy. Other biological effects of progesterone may exert a protective function in supporting pregnancy up to birth. Luteal phase support (LPS) with progesterone is the standard of care for assisted reproductive technology. Progesterone vaginal administration is currently the most widely used treatment for LPS. Physicians and patients have been reluctant to change an administration route that has proven to be effective. However, some questions remain open, namely the need for LPS in fresh and frozen embryo transfer, the route of administration, the optimal duration of LPS, dosage, and the benefit of combination therapies. The aim of this review is to provide an overview of the uterine and extra-uterine effects of progesterone that may play a role in embryo implantation and pregnancy, and to discuss the advantages of the use of progesterone for LPS in the context of Good Medical Practice.

Keywords: implantation; luteal phase support; progesterone; progesterone supplementation.

Figure 1

Progestagenic and estrogenic activity of various progestins. Reprinted from Ref. [114]. Copyright 1994, with permission from Elsevier.

Figure 2

Electromechanical activities of human uteri during the extracorporeal perfusion of human uteri. Silver-silver electrodes recorded the electrical signals, and intraluminal pressure probes detected the pressure variations [6].

Figure 3

(a) Frequency of uterine contractions detected in vivo in a cohort of menstruating women during the menstrual cycle detected with ultrasound (US) and Intrauterine Pressure detection (IUP); (b) Timings detected were menstrual cycle (mens), early follicular (EF), late follicular (LF), peri-ovulatory (PO), early luteal (EL), and late luteal (LL) phase of normal menstrual cycles. Adapted with permission from Ref. [62]. Copyright 2000, European Society of Human Reproduction and Embryology.

Figure 4

(a) The uterine slices after application into the vaginal collar of an extracorporeally perfused human uterus of radiolabeled progesterone (3H-P), used as a test substance, and 14C butanol, used as free diffusible reference substance, to calculate the P uterine pharmacokinetics and metabolism of the uterus; (b) The uptake of progesterone into the myometrium and endometrium after radiolabeled vaginal P application by autoradiography.