Progesterone is a steroid hormone derived from cholesterol that acts as a chemical messenger, playing a central role in the female reproductive system. After ovulation, the temporary structure known as the corpus luteum forms in the ovary and becomes the primary source of progesterone. This hormone prepares the body for a potential pregnancy by enacting changes within the uterus. If the ovary stopped releasing progesterone, the entire reproductive cycle and broader hormonal balance would be immediately disrupted.
Disruption of the Menstrual Cycle
The immediate consequence of progesterone cessation would be the destabilization of the uterine lining, or endometrium. Following ovulation, progesterone initiates the secretory phase, causing endometrial glands to secrete nutrients and blood vessels to grow. This transformation creates a thick, nourishing environment capable of supporting a fertilized egg.
Without progesterone, the developed endometrium cannot be sustained and rapidly breaks down. This collapse triggers withdrawal bleeding, the physiological mechanism of menstruation. The resulting bleeding would likely be irregular, potentially heavy, and occur prematurely, shortening the luteal phase. The absence of the hormone leads to menstrual irregularities or a complete lack of a normal cycle.
Failure to Achieve and Maintain Pregnancy
Progesterone is often called the “hormone of pregnancy” because it is necessary for both conception and gestation. Its primary function is to make the endometrium receptive to an embryo, a process called decidualization.
If the endometrium is not adequately prepared by progesterone, the fertilized egg cannot successfully embed into the uterine wall, resulting in implantation failure.
Even if implantation occurred, the pregnancy could not be sustained without the hormone. Progesterone maintains uterine quiescence by suppressing the contractility of the myometrium, the muscular layer of the uterus.
This suppression prevents the uterine muscle from contracting, which avoids spontaneous abortion or early miscarriage. A sudden drop in progesterone would immediately remove this “progesterone block,” leading to increased myometrial activity and the expulsion of the uterine contents.
In a normal pregnancy, the corpus luteum produces progesterone until the placenta takes over hormone production around the eighth to twelfth week of gestation. The cessation of ovarian progesterone release would cause an immediate loss of hormonal support for the embryo.
Any pregnancy would face a high risk of loss due to uterine contractions and the inability to maintain the nutrient-rich lining.
Broader Systemic Hormonal Imbalances
The hormone’s influence extends beyond the uterus and is integral to the wider endocrine system. Progesterone plays a significant role in the negative feedback loop of the Hypothalamic-Pituitary-Ovarian (HPO) axis.
High levels of progesterone signal back to the pituitary gland to reduce the secretion of Luteinizing Hormone (LH) and Follicle-Stimulating Hormone (FSH). The chronic absence of ovarian progesterone would disrupt this regulatory feedback, leading to aberrant signaling from the pituitary.
Progesterone also affects other tissues, including the development of the mammary glands for lactation. Chronic deficiency could affect bone health, as progesterone interacts with other sex steroids to contribute to bone mineral density.
The hormone also has neuroprotective effects and is associated with mood regulation. Its absence could contribute to alterations in emotional well-being and cognitive functions over the long term.