Progesterone
What is progesterone and why is it important?
Progesterone is produced by the corpus luteums (Latin for "yellow body"), and is a water producing hormone. This is the reason why the basal body temperature increases after ovulation. It makes the womb lining it optimum condition by making it thicken and form more arteries, so that an egg can attach itself and grow.
When an egg buries itself in the lining of the womb it secretes hCG (human chorion gonadotropin). hCG stimulates the corpus luteums to continue living beyond it’s normal life (2 weeks), produce more progesterone and making sure the pregnancy can go ahead.
Progesterone is vital to keeping a pregnancy. If the levels of progesterone fall during the pregnancy, abortion may be an unfortunate reality. The corpus luteums will produce progesterone until 10 – 12 weeks of pregnancy, after this the placenta takes over the progesterone production.
If the corpus luteums doesn’t get hCG stimulation in time from a fertilized egg, it will ”give up”, shrink and die. The gradually falling levels of progesterone will prepare the body for the next menstruation. When the levels are low enough, the lining of the womb will be pushed out (menstruation). Sufficient quantities of progesterone in enough days will stop the period from coming too early for the egg to attach. Too little progesterone in too few days can lead to (short luteal phases –link), and can make it problematic to get pregnant.
Progesterone is apparently also the partial reason for sore breasts, fatigue and other cycle related pains and known pregnancy symptoms.