If pregnancy occurs, the production of progesterone from the corpus luteum continues for 7 weeks because of the tonic release of luteinizing hormone (LH) from the pituitary gland (The corpus luteum will only survive for the first 6-10 weeks of a pregnancy). Studies show that after 7 weeks, the placenta takes over this function.
http://emedicine.medscape.com/article/254934-overview
In a quick summary, the luteal phase defect is a consequence of a follicular phase defect so that if there’s a low progesterone level which many people seem to associate low progesterone with progesterone that needs to be added back, most of the time that either means that the person did not ovulate or the ovulation came out of a follicle that was not a competent follicle to produce adequate amounts of progesterone.
http://www.obgyn.net/displaytranscript.asp?page=/avtranscripts/pcossandiego_thatcher
Menstrual Cycle and Miscarriage
Maximal progesterone induced blocking factor (protects the fetus from the mother's immune system) expression was observed when the hybridoma was cultured with 10(-10)M progesterone, compared to the control.
http://www.ncbi.nlm.nih.gov/pubmed/18619543
Progesterone is the precursor of the mineralocorticoid aldosterone, and after conversion to 17-hydroxyprogesterone (another natural progestogen), of cortisol and androstenedione. Androstenedione can be converted to testosterone, estrone and estradiol.
http://www.newworldencyclopedia.org/entry/Progesterone
- Progesterone is produced in the ovaries (specifically after ovulation in the corpus luteum), the brain, and, during pregnancy, in the placenta.
http://en.wikipedia.org/wiki/Progesterone
- A reason for poor progesterone production could be due to oxidative stress, free radicals, and high levels of lipoperoxide.
http://www.lifeissues.net/writers/feh/feh_15vitamin_c.html
- The baseline premenstrual dysphoria symptoms loneliness, crying, and skin blemishes with were statistically significantly and positively correlated with pregnanediol glucoronide (urinary metabolite of progesterone) levels in the cross-sectional study.
http://www.springerlink.com/content/2w26114203p87hw5/
- As progesterone decreases, GnRH rises and causes stimulation of LH and FSH. FSH causes maturation of follicles past the antral stage. The dominant follicle establishes itself and is the main follicle that grows. The growing follicle produces estrogen in the granulosa cells. Estrogen actually peaks before heat (estrus) and it is the estrogen that causes the final LH release.
- Mean hCG levels reach a maximum at week 8, progesterone levels reach the nadir at week 7 and increase after that.
http://humrep.oxfordjournals.org/cgi/content/full/den299